<?php
/**
* PHP implementation of the JSON-LD API.
*
* @author Dave Longley
*
* BSD 3-Clause License
* Copyright (c) 2011-2012 Digital Bazaar, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of the Digital Bazaar, Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* Performs JSON-LD compaction.
*
* @param mixed $input the JSON-LD object to compact.
* @param mixed $ctx the context to compact with.
* @param assoc [$options] options to use:
* [base] the base IRI to use.
* [strict] use strict mode (default: true).
* [optimize] true to optimize the compaction (default: false).
* [graph] true to always output a top-level graph (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return mixed the compacted JSON-LD output.
*/
function jsonld_compact($input, $ctx, $options=array()) {
$p = new JsonLdProcessor();
return $p->compact($input, $ctx, $options);
}
/**
* Performs JSON-LD expansion.
*
* @param mixed $input the JSON-LD object to expand.
* @param assoc[$options] the options to use:
* [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array the expanded JSON-LD output.
*/
function jsonld_expand($input, $options=array()) {
$p = new JsonLdProcessor();
return $p->expand($input, $options);
}
/**
* Performs JSON-LD framing.
*
* @param mixed $input the JSON-LD object to frame.
* @param stdClass $frame the JSON-LD frame to use.
* @param assoc [$options] the framing options.
* [base] the base IRI to use.
* [embed] default @embed flag (default: true).
* [explicit] default @explicit flag (default: false).
* [omitDefault] default @omitDefault flag (default: false).
* [optimize] optimize when compacting (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return stdClass the framed JSON-LD output.
*/
function jsonld_frame($input, $frame, $options=array()) {
$p = new JsonLdProcessor();
return $p->frame($input, $frame, $options);
}
/**
* Performs JSON-LD normalization.
*
* @param mixed $input the JSON-LD object to normalize.
* @param assoc [$options] the options to use:
* [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array the normalized JSON-LD output.
*/
function jsonld_normalize($input, $options=array()) {
$p = new JsonLdProcessor();
return $p->normalize($input, $options);
}
/**
* Outputs the RDF statements found in the given JSON-LD object.
*
* @param mixed $input the JSON-LD object.
* @param assoc [$options] the options to use:
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array all RDF statements in the JSON-LD object.
*/
function jsonld_to_rdf($input, $options=array()) {
$p = new JsonLdProcessor();
return $p->toRdf($input, $options);
}
/**
* Processes a local context, resolving any URLs as necessary, and returns a
* new active context.
*
* @param active_ctx the current active context.
* @param local_ctx the local context to process.
* @param [options] the options to use:
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return the new active context.
*/
function jsonld_process_context($active_ctx, $local_ctx, $options=array()) {
$p = new JsonLdProcessor();
return $p->processContext($active_ctx, $local_ctx, $options);
}
/**
* A JSON-LD processor.
*/
class JsonLdProcessor {
/** XSD constants */
const XSD_BOOLEAN = 'http://www.w3.org/2001/XMLSchema#boolean';
const XSD_DOUBLE = 'http://www.w3.org/2001/XMLSchema#double';
const XSD_INTEGER = 'http://www.w3.org/2001/XMLSchema#integer';
/** RDF constants */
const RDF_FIRST = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#first';
const RDF_REST = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#rest';
const RDF_NIL = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil';
const RDF_TYPE = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
/**
* Constructs a JSON-LD processor.
*/
public function __construct() {}
/**
* Performs JSON-LD compaction.
*
* @param mixed $input the JSON-LD object to compact.
* @param mixed $ctx the context to compact with.
* @param assoc $options the compaction options.
* [activeCtx] true to also return the active context used.
*
* @return mixed the compacted JSON-LD output.
*/
public function compact($input, $ctx, $options) {
// nothing to compact
if($input === null) {
return null;
}
// set default options
isset($options['base']) or $options['base'] = '';
isset($options['strict']) or $options['strict'] = true;
isset($options['optimize']) or $options['optimize'] = false;
isset($options['graph']) or $options['graph'] = false;
isset($options['activeCtx']) or $options['activeCtx'] = false;
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// expand input
try {
$expanded = $this->expand($input, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not expand input before compaction.',
'jsonld.CompactError', null, $e);
}
// process context
$active_ctx = $this->_getInitialContext();
try {
$active_ctx = $this->processContext($active_ctx, $ctx, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not merge context before compaction.',
'jsonld.CompactError', null, $e);
}
// do compaction
$compacted = $this->_compact($active_ctx, null, $expanded, $options);
// always use an array if graph options is on
if($options['graph'] === true) {
$compacted = self::arrayify($compacted);
}
// else if compacted is an array with 1 entry, remove array
else if(is_array($compacted) && count($compacted) === 1) {
$compacted = $compacted[0];
}
// follow @context key
if(is_object($ctx) && property_exists($ctx, '@context')) {
$ctx = $ctx->{'@context'};
}
// build output context
$ctx = self::copy($ctx);
$ctx = self::arrayify($ctx);
// remove empty contexts
$tmp = $ctx;
$ctx = array();
foreach($tmp as $i => $v) {
if(!is_object($v) || count(get_object_vars($v)) > 0) {
$ctx[] = $v;
}
}
// remove array if only one context
$ctx_length = count($ctx);
$has_context = ($ctx_length > 0);
if($ctx_length === 1) {
$ctx = $ctx[0];
}
// add context
if($has_context || $options['graph']) {
if(is_array($compacted)) {
// use '@graph' keyword
$kwgraph = $this->_compactIri($active_ctx, '@graph');
$graph = $compacted;
$compacted = new stdClass();
if($has_context) {
$compacted->{'@context'} = $ctx;
}
$compacted->{$kwgraph} = $graph;
}
else if(is_object($compacted)) {
// reorder keys so @context is first
$graph = $compacted;
$compacted = new stdClass();
$compacted->{'@context'} = $ctx;
foreach($graph as $k => $v) {
$compacted->{$k} = $v;
}
}
}
if($options['activeCtx']) {
return array(
'compacted' => $compacted,
'activeCtx' => $active_ctx);
}
else {
return $compacted;
}
}
/**
* Performs JSON-LD expansion.
*
* @param mixed $input the JSON-LD object to expand.
* @param assoc $options the options to use:
* [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array the expanded JSON-LD output.
*/
public function expand($input, $options) {
// set default options
isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// resolve all @context URLs in the input
$input = self::copy($input);
$this->_resolveUrls($input, $options['resolver']);
// do expansion
$ctx = $this->_getInitialContext();
$expanded = $this->_expand($ctx, null, $input, $options, false);
// optimize away @graph with no other properties
if(is_object($expanded) && property_exists($expanded, '@graph') &&
count(get_object_vars($expanded)) === 1) {
$expanded = $expanded->{'@graph'};
}
// normalize to an array
return self::arrayify($expanded);
}
/**
* Performs JSON-LD framing.
*
* @param mixed $input the JSON-LD object to frame.
* @param stdClass $frame the JSON-LD frame to use.
* @param $options the framing options.
* [base] the base IRI to use.
* [embed] default @embed flag (default: true).
* [explicit] default @explicit flag (default: false).
* [omitDefault] default @omitDefault flag (default: false).
* [optimize] optimize when compacting (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return stdClass the framed JSON-LD output.
*/
public function frame($input, $frame, $options) {
// set default options
isset($options['base']) or $options['base'] = '';
isset($options['embed']) or $options['embed'] = true;
isset($options['explicit']) or $options['explicit'] = false;
isset($options['omitDefault']) or $options['omitDefault'] = false;
isset($options['optimize']) or $options['optimize'] = false;
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// preserve frame context
$ctx = (property_exists($frame, '@context') ?
$frame->{'@context'} : new stdClass());
try {
// expand input
$_input = $this->expand($input, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not expand input before framing.',
'jsonld.FrameError', $e);
}
try {
// expand frame
$_frame = $this->expand($frame, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not expand frame before framing.',
'jsonld.FrameError', $e);
}
// do framing
$framed = $this->_frame($_input, $_frame, $options);
try {
// compact result (force @graph option to true)
$options['graph'] = true;
$options['activeCtx'] = true;
$result = $this->compact($framed, $ctx, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not compact framed output.',
'jsonld.FrameError', $e);
}
$compacted = $result['compacted'];
$ctx = $result['activeCtx'];
// get graph alias
$graph = $this->_compactIri($ctx, '@graph');
// remove @preserve from results
$compacted->{$graph} = $this->_removePreserve($ctx, $compacted->{$graph});
return $compacted;
}
/**
* Performs JSON-LD normalization.
*
* @param mixed $input the JSON-LD object to normalize.
* @param assoc $options the options to use:
* [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array the JSON-LD normalized output.
*/
public function normalize($input, $options) {
// set default options
isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
try {
// expand input then do normalization
$expanded = $this->expand($input, $options);
}
catch(JsonLdException $e) {
throw new JsonLdException(
'Could not expand input before normalization.',
'jsonld.NormalizeError', $e);
}
// do normalization
return $this->_normalize($expanded);
}
/**
* Outputs the RDF statements found in the given JSON-LD object.
*
* @param mixed $input the JSON-LD object.
* @param assoc $options the options to use:
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return array the RDF statements.
*/
public function toRDF($input, $options) {
// set default options
isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// resolve all @context URLs in the input
$input = self::copy($input);
$this->_resolveUrls($input, $options['resolver']);
// output RDF statements
return $this->_toRDF($input);
}
/**
* Processes a local context, resolving any URLs as necessary, and returns a
* new active context in its callback.
*
* @param stdClass $active_ctx the current active context.
* @param mixed $local_ctx the local context to process.
* @param assoc $options the options to use:
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
*
* @return stdClass the new active context.
*/
public function processContext($active_ctx, $local_ctx) {
// return initial context early for null context
if($local_ctx === null) {
return $this->_getInitialContext();
}
// set default options
isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// resolve URLs in localCtx
$local_ctx = self::copy($local_ctx);
if(is_object($local_ctx) && !property_exists($local_ctx, '@context')) {
$local_ctx = (object)array('@context' => $local_ctx);
}
$ctx = $this->_resolveUrls($local_ctx, $options['resolver']);
// process context
return $this->_processContext($active_ctx, $ctx, $options);
}
/**
* Returns true if the given subject has the given property.
*
* @param stdClass $subject the subject to check.
* @param string $property the property to look for.
*
* @return bool true if the subject has the given property, false if not.
*/
public static function hasProperty($subject, $property) {
$rval = false;
if(property_exists($subject, $property)) {
$value = $subject->{$property};
$rval = (!is_array($value) || count($value) > 0);
}
return $rval;
}
/**
* Determines if the given value is a property of the given subject.
*
* @param stdClass $subject the subject to check.
* @param string $property the property to check.
* @param mixed $value the value to check.
*
* @return bool true if the value exists, false if not.
*/
public static function hasValue($subject, $property, $value) {
$rval = false;
if(self::hasProperty($subject, $property)) {
$val = $subject->{$property};
$isList = self::_isListValue($val);
if(is_array($val) || $isList) {
if($isList) {
$val = $val->{'@list'};
}
foreach($val as $v) {
if(self::compareValues($value, $v)) {
$rval = true;
break;
}
}
}
// avoid matching the set of values with an array value parameter
else if(!is_array($value)) {
$rval = self::compareValues($value, $val);
}
}
return $rval;
}
/**
* Adds a value to a subject. If the subject already has the value, it will
* not be added. If the value is an array, all values in the array will be
* added.
*
* Note: If the value is a subject that already exists as a property of the
* given subject, this method makes no attempt to deeply merge properties.
* Instead, the value will not be added.
*
* @param stdClass $subject the subject to add the value to.
* @param string $property the property that relates the value to the subject.
* @param mixed $value the value to add.
* @param bool [$propertyIsArray] true if the property is always an array,
* false if not (default: false).
*/
public static function addValue(
$subject, $property, $value, $propertyIsArray=false) {
if(is_array($value)) {
if(count($value) === 0 && $propertyIsArray &&
!property_exists($subject, $property)) {
$subject->{$property} = array();
}
foreach($value as $v) {
self::addValue($subject, $property, $v, $propertyIsArray);
}
}
else if(property_exists($subject, $property)) {
$has_value = self::hasValue($subject, $property, $value);
// make property an array if value not present or always an array
if(!is_array($subject->{$property}) &&
(!$has_value || $propertyIsArray)) {
$subject->{$property} = array($subject->{$property});
}
// add new value
if(!$has_value) {
$subject->{$property}[] = $value;
}
}
else {
// add new value as set or single value
$subject->{$property} = $propertyIsArray ? array($value) : $value;
}
}
/**
* Gets all of the values for a subject's property as an array.
*
* @param stdClass $subject the subject.
* @param string $property the property.
*
* @return array all of the values for a subject's property as an array.
*/
public static function getValues($subject, $property) {
$rval = $subject->{$property} ?: array();
return self::arrayify($rval);
}
/**
* Removes a property from a subject.
*
* @param stdClass $subject the subject.
* @param string $property the property.
*/
public static function removeProperty($subject, $property) {
unset($subject->{$property});
}
/**
* Removes a value from a subject.
*
* @param stdClass $subject the subject.
* @param string $property the property that relates the value to the subject.
* @param mixed $value the value to remove.
* @param bool [$propertyIsArray] true if the property is always an array,
* false if not (default: false).
*/
public static function removeValue(
$subject, $property, $value, $propertyIsArray=false) {
// filter out value
$filter = function($e) use ($value) {
return !self::compareValues($e, $value);
};
$values = self::getValues($subject, $property);
$values = array_filter($values, $filter);
if(count($values) === 0) {
self::removeProperty($subject, $property);
}
else if(count($values) === 1 && !$propertyIsArray) {
$subject->{$property} = $values[0];
}
else {
$subject->{$property} = $values;
}
}
/**
* Compares two JSON-LD values for equality. Two JSON-LD values will be
* considered equal if:
*
* 1. They are both primitives of the same type and value.
* 2. They are both @values with the same @value, @type, and @language, OR
* 3. They both have @ids they are the same.
*
* @param mixed $v1 the first value.
* @param mixed $v2 the second value.
*
* @return bool true if v1 and v2 are considered equal, false if not.
*/
public static function compareValues($v1, $v2) {
// 1. equal primitives
if($v1 === $v2) {
return true;
}
// 2. equal @values
if(self::_isValue($v1) && self::_isValue($v2) &&
$v1->{'@value'} === $v2->{'@value'} &&
property_exists($v1, '@type') === property_exists($v2, '@type') &&
property_exists($v1, '@language') === property_exists($v2, '@language') &&
(!property_exists($v1, '@type') || $v1->{'@type'} === $v2->{'@type'}) &&
(!property_exists($v1, '@language') ||
$v2->{'@language'} === $v2->{'@language'})) {
return true;
}
// 3. equal @ids
if(is_object($v1) && property_exists($v1, '@id') &&
is_object($v2) && property_exists($v2, '@id')) {
return $v1->{'@id'} === $v2->{'@id'};
}
return false;
}
/**
* Compares two JSON-LD normalized inputs for equality.
*
* @param array $n1 the first normalized input.
* @param array $n2 the second normalized input.
*
* @return bool true if the inputs are equivalent, false if not.
*/
public static function compareNormalized($n1, $n2) {
if(!is_array($n1) || !is_array($n2)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; normalized JSON-LD must be an array.',
'jsonld.SyntaxError');
}
// different # of subjects
if(count($n1) !== count($n2)) {
return false;
}
// assume subjects are in the same order because of normalization
foreach($n1 as $i => $s1) {
$s2 = $n2[$i];
// different @ids
if($s1->{'@id'} !== $s2->{'@id'}) {
return false;
}
// subjects have different properties
if(count(get_object_vars($s1)) !== count(get_object_vars($s2))) {
return false;
}
foreach($s1 as $p => $objects) {
// skip @id property
if($p === '@id') {
continue;
}
// s2 is missing s1 property
if(!self::hasProperty($s2, $p)) {
return false;
}
// subjects have different objects for the property
if(count($objects) !== count($s2->{$p})) {
return false;
}
foreach($objects as $oi => $o) {
// s2 is missing s1 object
if(!self::hasValue($s2, $p, $o)) {
return false;
}
}
}
}
return true;
}
/**
* Gets the value for the given active context key and type, null if none is
* set.
*
* @param stdClass $ctx the active context.
* @param string $key the context key.
* @param string [$type] the type of value to get (eg: '@id', '@type'), if not
* specified gets the entire entry for a key, null if not found.
*
* @return mixed the value.
*/
public static function getContextValue($ctx, $key, $type) {
$rval = null;
// return null for invalid key
if($key === null) {
return $rval;
}
// get default language
if($type === '@language' && property_exists($ctx, $type)) {
$rval = $ctx->{$type};
}
// get specific entry information
if(property_exists($ctx->mappings, $key)) {
$entry = $ctx->mappings->{$key};
// return whole entry
if($type === null) {
$rval = $entry;
}
// return entry value for type
else if(property_exists($entry, $type)) {
$rval = $entry->{$type};
}
}
return $rval;
}
/**
* If $value is an array, returns $value, otherwise returns an array
* containing $value as the only element.
*
* @param mixed $value the value.
*
* @return an array.
*/
public static function arrayify($value) {
if(is_array($value)) {
return $value;
}
return array($value);
}
/**
* Clones an object, array, or string/number.
*
* @param mixed $value the value to clone.
*
* @return mixed the cloned value.
*/
public static function copy($value) {
if(is_object($value) || is_array($value)) {
return unserialize(serialize($value));
}
else {
return $value;
}
}
/**
* Recursively compacts an element using the given active context. All values
* must be in expanded form before this method is called.
*
* @param stdClass $ctx the active context to use.
* @param mixed $property the property that points to the element, null for
* none.
* @param mixed $element the element to compact.
* @param array $options the compaction options.
*
* @return mixed the compacted value.
*/
protected function _compact($ctx, $property, $element, $options) {
// recursively compact array
if(is_array($element)) {
$rval = array();
foreach($element as $e) {
$e = $this->_compact($ctx, $property, $e, $options);
// drop null values
if($e !== null) {
$rval[] = $e;
}
}
if(count($rval) === 1) {
// use single element if no container is specified
$container = self::getContextValue($ctx, $property, '@container');
if($container !== '@list' && $container !== '@set') {
$rval = $rval[0];
}
}
return $rval;
}
// recursively compact object
if(is_object($element)) {
// element is a @value
if(self::_isValue($element)) {
$type = self::getContextValue($ctx, $property, '@type');
$language = self::getContextValue($ctx, $property, '@language');
// matching @type specified in context, compact element
if($type !== null &&
property_exists($element, '@type') && $element->{'@type'} === $type) {
$element = $element->{'@value'};
// use native datatypes for certain xsd types
if($type === self::XSD_BOOLEAN) {
$element = !($element === 'false' || $element === '0');
}
else if($type === self::XSD_INTEGER) {
$element = intval($element);
}
else if($type === self::XSD_DOUBLE) {
$element = doubleval($element);
}
}
// matching @language specified in context, compact element
else if($language !== null &&
property_exists($element, '@language') &&
$element->{'@language'} === $language) {
$element = $element->{'@value'};
}
// compact @type IRI
else if(property_exists($element, '@type')) {
$element->{'@type'} = $this->_compactIri($ctx, $element->{'@type'});
}
return $element;
}
// compact subject references
if(self::_isSubjectReference($element)) {
$type = self::getContextValue($ctx, $property, '@type');
if($type === '@id') {
$element = $this->_compactIri($ctx, $element->{'@id'});
return $element;
}
}
// recursively process element keys
$rval = new stdClass();
foreach($element as $key => $value) {
// compact @id and @type(s)
if($key === '@id' || $key === '@type') {
// compact single @id
if(is_string($value)) {
$value = $this->_compactIri($ctx, $value);
}
// value must be a @type array
else {
$types = array();
foreach($value as $v) {
$types[] = $this->_compactIri($ctx, $v);
}
$value = $types;
}
// compact property and add value
$prop = $this->_compactIri($ctx, $key);
$isArray = (is_array($value) && count($value) === 0);
self::addValue($rval, $prop, $value, $isArray);
continue;
}
// Note: value must be an array due to expansion algorithm.
// preserve empty arrays
if(count($value) === 0) {
$prop = $this->_compactIri($ctx, $key);
self::addValue($rval, $prop, array(), true);
}
// recusively process array values
foreach($value as $v) {
$isList = self::_isListValue($v);
// compact property
$prop = $this->_compactIri($ctx, $key, $v);
// remove @list for recursion (will be re-added if necessary)
if($isList) {
$v = $v->{'@list'};
}
// recursively compact value
$v = $this->_compact($ctx, $prop, $v, $options);
// get container type for property
$container = self::getContextValue($ctx, $prop, '@container');
// handle @list
if($isList && $container !== '@list') {
// handle messy @list compaction
if(property_exists($rval, $prop) && $options['strict']) {
throw new JsonLdException(
'JSON-LD compact error; property has a "@list" @container ' +
'rule but there is more than a single @list that matches ' +
'the compacted term in the document. Compaction might mix ' +
'unwanted items into the list.',
'jsonld.SyntaxError');
}
// reintroduce @list keyword
$kwlist = $this->_compactIri($ctx, '@list');
$val = new stdClass();
$val->{$kwlist} = $v;
$v = $val;
}
// if @container is @set or @list or value is an empty array, use
// an array when adding value
$isArray = ($container === '@set' || $container === '@list' ||
(is_array($v) && count($v) === 0));
// add compact value
self::addValue($rval, $prop, $v, $isArray);
}
}
return $rval;
}
// only primitives remain which are already compact
return $element;
}
/**
* Recursively expands an element using the given context. Any context in
* the element will be removed. All context URLs must have been resolved
* before calling this method.
*
* @param stdClass $ctx the context to use.
* @param mixed $property the property for the element, null for none.
* @param mixed $element the element to expand.
* @param array $options the expansion options.
* @param bool $propertyIsList true if the property is a list, false if not.
*
* @return mixed the expanded value.
*/
protected function _expand(
$ctx, $property, $element, $options, $propertyIsList) {
// recursively expand array
if(is_array($element)) {
$rval = array();
foreach($element as $e) {
// expand element
$e = $this->_expand($ctx, $property, $e, $options, $propertyIsList);
if(is_array($e) && $propertyIsList) {
// lists of lists are illegal
throw new JsonLdException(
'Invalid JSON-LD syntax; lists of lists are not permitted.',
'jsonld.SyntaxError');
}
// drop null values
else if($e !== null) {
$rval[] = $e;
}
}
return $rval;
}
// recursively expand object
if(is_object($element)) {
// if element has a context, process it
if(property_exists($element, '@context')) {
$ctx = $this->_processContext($ctx, $element->{'@context'}, $options);
unset($element->{'@context'});
}
$rval = new stdClass();
foreach($element as $key => $value) {
// expand property
$prop = $this->_expandTerm($ctx, $key);
// drop non-absolute IRI keys that aren't keywords
if(!self::_isAbsoluteIri($prop) && !self::_isKeyword($prop, $ctx)) {
continue;
}
// if value is null and property is not @value, continue
$value = $element->{$key};
if($value === null && $prop !== '@value') {
continue;
}
// syntax error if @id is not a string
if($prop === '@id' && !is_string($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; "@id" value must a string.',
'jsonld.SyntaxError', array('value' => $value));
}
// @type must be a string, array of strings, or an empty JSON object
if($prop === '@type' &&
!(is_string($value) || self::_isArrayOfStrings($value) ||
self::_isEmptyObject($value))) {
throw new JsonLdException(
'Invalid JSON-LD syntax; "@type" value must a string, an array ' +
'of strings, or an empty object.',
'jsonld.SyntaxError', array('value' => $value));
}
// @graph must be an array or an object
if($prop === '@graph' && !(is_object($value) || is_array($value))) {
throw new JsonLdException(
'Invalid JSON-LD syntax; "@value" value must not be an ' +
'object or an array.',
'jsonld.SyntaxError', array('value' => $value));
}
// @value must not be an object or an array
if($prop === '@value' && (is_object($value) || is_array($value))) {
throw new JsonLdException(
'Invalid JSON-LD syntax; "@value" value must not be an ' +
'object or an array.',
'jsonld.SyntaxError', array('value' => $value));
}
// @language must be a string
if($prop === '@language' && !is_string($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; "@language" value must not be a string.',
'jsonld.SyntaxError', array('value' => $value));
}
// recurse into @list, @set, or @graph, keeping the active property
$isList = ($prop === '@list');
if($isList || $prop === '@set' || $prop === '@graph') {
$value = $this->_expand($ctx, $property, $value, $options, $isList);
if($isList && self::_isListValue($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; lists of lists are not permitted.',
'jsonld.SyntaxError');
}
}
else {
// update active property and recursively expand value
$property = $key;
$value = $this->_expand($ctx, $property, $value, $options, false);
}
// drop null values if property is not @value (dropped below)
if($value !== null || $prop === '@value') {
// convert value to @list if container specifies it
if($prop !== '@list' && !self::_isListValue($value)) {
$container = self::getContextValue($ctx, $property, '@container');
if($container === '@list') {
// ensure value is an array
$value = (object)array('@list' => self::arrayify($value));
}
}
// add value, use an array if not @id, @type, @value, or @language
$useArray = !($prop === '@id' || $prop === '@type' ||
$prop === '@value' || $prop === '@language');
self::addValue($rval, $prop, $value, $useArray);
}
}
// get property count on expanded output
$count = count(get_object_vars($rval));
// @value must only have @language or @type
if(property_exists($rval, '@value')) {
if(($count === 2 && !property_exists($rval, '@type') &&
!property_exists($rval, '@language')) ||
$count > 2) {
throw new JsonLdException(
'Invalid JSON-LD syntax; an element containing "@value" must have ' +
'at most one other property which can be "@type" or "@language".',
'jsonld.SyntaxError', array('element' => $rval));
}
// value @type must be a string
if(property_exists($rval, '@type') && !is_string($rval->{'@type'})) {
throw new JsonLdException(
'Invalid JSON-LD syntax; the "@type" value of an element ' +
'containing "@value" must be a string.',
'jsonld.SyntaxError', array('element' => $rval));
}
// return only the value of @value if there is no @type or @language
else if($count === 1) {
$rval = $rval->{'@value'};
}
// drop null @values
else if($rval->{'@value'} === null) {
$rval = null;
}
}
// convert @type to an array
else if(property_exists($rval, '@type') && !is_array($rval->{'@type'})) {
$rval->{'@type'} = array($rval->{'@type'});
}
// handle @set and @list
else if(property_exists($rval, '@set') ||
property_exists($rval, '@list')) {
if($count !== 1) {
throw new JsonLdException(
'Invalid JSON-LD syntax; if an element has the property "@set" ' +
'or "@list", then it must be its only property.',
'jsonld.SyntaxError', array('element' => $rval));
}
// optimize away @set
if(property_exists($rval, '@set')) {
$rval = $rval->{'@set'};
}
}
// drop objects with only @language
else if(property_exists($rval, '@language') && $count === 1) {
$rval = null;
}
return $rval;
}
// expand element according to value expansion rules
return $this->_expandValue($ctx, $property, $element, $options['base']);
}
/**
* Performs JSON-LD framing.
*
* @param array $input the expanded JSON-LD to frame.
* @param array $frame the expanded JSON-LD frame to use.
* @param array $options the framing options.
*
* @return array the framed output.
*/
protected function _frame($input, $frame, $options) {
// create framing state
$state = (object)array(
'options' => $options,
'subjects' => new stdClass());
// produce a map of all subjects and name each bnode
$namer = new UniqueNamer('_:t');
$this->_flatten($state->subjects, $input, $namer, null, null);
// frame the subjects
$framed = new ArrayObject();
$this->_match_frame(
$state, array_keys((array)$state->subjects), $frame, $framed, null);
return (array)$framed;
}
/**
* Performs JSON-LD normalization.
*
* @param input the expanded JSON-LD object to normalize.
*
* @return the normalized output.
*/
protected function _normalize($input) {
// get statements
$namer = new UniqueNamer('_:t');
$bnodes = new stdClass();
$subjects = new stdClass();
$this->_getStatements($input, $namer, $bnodes, $subjects);
// create canonical namer
$namer = new UniqueNamer('_:c14n');
// continue to hash bnode statements while bnodes are assigned names
$unnamed = null;
$nextUnnamed = array_keys((array)$bnodes);
$duplicates = null;
do {
$unnamed = $nextUnnamed;
$nextUnnamed = array();
$duplicates = new stdClass();
$unique = new stdClass();
foreach($unnamed as $bnode) {
// hash statements for each unnamed bnode
$statements = $bnodes->{$bnode};
$hash = $this->_hashStatements($statements, $namer);
// store hash as unique or a duplicate
if(property_exists($duplicates, $hash)) {
$duplicates->{$hash}[] = $bnode;
$nextUnnamed[] = $bnode;
}
else if(property_exists($unique, $hash)) {
$duplicates->{$hash} = array($unique->{$hash}, $bnode);
$nextUnnamed[] = $unique->{$hash};
$nextUnnamed[] = $bnode;
unset($unique->{$hash});
}
else {
$unique->{$hash} = $bnode;
}
}
// name unique bnodes in sorted hash order
$hashes = array_keys((array)$unique);
sort($hashes);
foreach($hashes as $hash) {
$namer->getName($unique->{$hash});
}
}
while(count($unnamed) > count($nextUnnamed));
// enumerate duplicate hash groups in sorted order
$hashes = array_keys((array)$duplicates);
sort($hashes);
foreach($hashes as $hash) {
// process group
$group = $duplicates->{$hash};
$results = array();
foreach($group as $bnode) {
// skip already-named bnodes
if($namer->isNamed($bnode)) {
continue;
}
// hash bnode paths
$path_namer = new UniqueNamer('_:t');
$path_namer->getName($bnode);
$results[] = $this->_hashPaths(
$bnodes, $bnodes->{$bnode}, $namer, $path_namer);
}
// name bnodes in hash order
usort($results, function($a, $b) {
$a = $a->hash;
$b = $b->hash;
return ($a < $b) ? -1 : (($a > $b) ? 1 : 0);
});
foreach($results as $result) {
// name all bnodes in path namer in key-entry order
foreach($result->pathNamer->order as $bnode) {
$namer->getName($bnode);
}
}
}
// create JSON-LD array
$output = array();
// add all bnodes
foreach($bnodes as $id => $statements) {
// add all property statements to bnode
$bnode = (object)array('@id' => $namer->getName($id));
foreach($statements as $statement) {
if($statement->s === '_:a') {
$z = $this->_getBlankNodeName($statement->o);
$o = $z ? (object)array('@id' => $namer->getName($z)) : $statement->o;
self::addValue($bnode, $statement->p, $o, true);
}
}
$output[] = $bnode;
}
// add all non-bnodes
foreach($subjects as $id => $statements) {
// add all statements to subject
$subject = (object)array('@id' => $id);
foreach($statements as $statement) {
$z = $this->_getBlankNodeName($statement->o);
$o = $z ? (object)array('@id' => $namer->getName($z)) : $statement->o;
self::addValue($subject, $statement->p, $o, true);
}
$output[] = $subject;
}
// sort normalized output by @id
usort($output, function($a, $b) {
$a = $a->{'@id'};
$b = $b->{'@id'};
return ($a < $b) ? -1 : (($a > $b) ? 1 : 0);
});
return $output;
}
/**
* Outputs the RDF statements found in the given JSON-LD object.
*
* @param mixed $input the JSON-LD object.
*
* @return array the RDF statements.
*/
protected function _toRDF($input) {
// FIXME: implement
throw new JsonLdException('Not implemented', 'jsonld.NotImplemented');
}
/**
* Processes a local context and returns a new active context.
*
* @param stdClass $active_ctx the current active context.
* @param mixed $local_ctx the local context to process.
* @param array $options the context processing options.
*
* @return stdClass the new active context.
*/
protected function _processContext($active_ctx, $local_ctx, $options) {
// initialize the resulting context
$rval = self::copy($active_ctx);
// normalize local context to an array
$ctxs = self::arrayify($local_ctx);
// process each context in order
foreach($ctxs as $ctx) {
// reset to initial context
if($ctx === null) {
$rval = $this->_getInitialContext();
continue;
}
// dereference @context key if present
if(is_object($ctx) && property_exists($ctx, '@context')) {
$ctx = $ctx->{'@context'};
}
// context must be an object by now, all URLs resolved before this call
if(!is_object($ctx)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context must be an object.',
'jsonld.SyntaxError', array('context' => $ctx));
}
// define context mappings for keys in local context
$defined = new stdClass();
foreach($ctx as $k => $v) {
$this->_defineContextMapping(
$rval, $ctx, $k, $options['base'], $defined);
}
}
return $rval;
}
/**
* Expands the given value by using the coercion and keyword rules in the
* given context.
*
* @param stdClass $ctx the active context to use.
* @param string $property the property the value is associated with.
* @param mixed $value the value to expand.
* @param string $base the base IRI to use.
*
* @return mixed the expanded value.
*/
protected function _expandValue($ctx, $property, $value, $base) {
// default to simple string return value
$rval = $value;
// special-case expand @id and @type (skips '@id' expansion)
$prop = $this->_expandTerm($ctx, $property);
if($prop === '@id') {
$rval = $this->_expandTerm($ctx, $value, $base);
}
else if($prop === '@type') {
$rval = $this->_expandTerm($ctx, $value);
}
else {
// get type definition from context
$type = self::getContextValue($ctx, $property, '@type');
// do @id expansion
if($type === '@id') {
$rval = (object)array('@id' => $this->_expandTerm($ctx, $value, $base));
}
// other type
else if($type !== null) {
$rval = (object)array('@value' => strval($value), '@type' => $type);
}
// check for language tagging
else {
$language = self::getContextValue($ctx, $property, '@language');
if($language !== null) {
$rval = (object)array(
'@value' => strval($value), '@language' => $language);
}
}
}
return $rval;
}
/**
* Recursively gets all statements from the given expanded JSON-LD input.
*
* @param mixed $input the valid expanded JSON-LD input.
* @param UniqueNamer $namer the namer to use when encountering blank nodes.
* @param stdClass $bnodes the blank node statements map to populate.
* @param stdClass $subjects the subject statements map to populate.
* @param mixed [$name] the name (@id) assigned to the current input.
*/
protected function _getStatements(
$input, $namer, $bnodes, $subjects, $name=null) {
// recurse into arrays
if(is_array($input)) {
foreach($input as $e) {
$this->_getStatements($e, $namer, $bnodes, $subjects);
}
}
// safe to assume input is a subject/blank node
else {
$isBnode = self::_isBlankNode($input);
// name blank node if appropriate, use passed name if given
if($name === null) {
if(property_exists($input, '@id')) {
$name = $input->{'@id'};
}
if($isBnode) {
$name = $namer->getName($name);
}
}
// use a subject of '_:a' for blank node statements
$s = $isBnode ? '_:a' : $name;
// get statements for the blank node
$entries;
if($isBnode) {
if(!property_exists($bnodes, $name)) {
$entries = $bnodes->{$name} = new ArrayObject();
}
else {
$entries = $bnodes->{$name};
}
}
else if(!property_exists($subjects, $name)) {
$entries = $subjects->{$name} = new ArrayObject();
}
else {
$entries = $subjects->{$name};
}
// add all statements in input
foreach($input as $p => $objects) {
// skip @id
if($p === '@id') {
continue;
}
// convert @lists into embedded blank node linked lists
foreach($objects as $i => $o) {
if(self::_isListValue($o)) {
$objects[$i] = $this->_makeLinkedList($o);
}
}
foreach($objects as $o) {
// convert boolean to @value
if(is_bool($o)) {
$o = (object)array(
'@value' => ($o ? 'true' : 'false'),
'@type' => self::XSD_BOOLEAN);
}
// convert double to @value
else if(is_double($o)) {
// do special JSON-LD double format, printf('%1.16e') equivalent
$o = preg_replace('/(e(?:\+|-))([0-9])$/', '${1}0${2}',
sprintf('%1.16e', $o));
$o = (object)array('@value' => $o, '@type' => self::XSD_DOUBLE);
}
// convert integer to @value
else if(is_integer($o)) {
$o = (object)array(
'@value' => strval($o), '@type' => self::XSD_INTEGER);
}
// object is a blank node
if(self::_isBlankNode($o)) {
// name object position blank node
$o_name = property_exists($o, '@id') ? $o->{'@id'} : null;
$o_name = $namer->getName($o_name);
// add property statement
$this->_addStatement($entries, (object)array(
's' => $s, 'p' => $p, 'o' => (object)array('@id' => $o_name)));
// add reference statement
if(!property_exists($bnodes, $o_name)) {
$o_entries = $bnodes->{$o_name} = new ArrayObject();
}
else {
$o_entries = $bnodes->{$o_name};
}
$this->_addStatement(
$o_entries, (object)array(
's' => $name, 'p' => $p, 'o' => (object)array('@id' => '_:a')));
// recurse into blank node
$this->_getStatements($o, $namer, $bnodes, $subjects, $o_name);
}
// object is a string, @value, subject reference
else if(is_string($o) || self::_isValue($o) ||
self::_isSubjectReference($o)) {
// add property statement
$this->_addStatement($entries, (object)array(
's' => $s, 'p' => $p, 'o' => $o));
// ensure a subject entry exists for subject reference
if(self::_isSubjectReference($o) &&
!property_exists($subjects, $o->{'@id'})) {
$subjects->{$o->{'@id'}} = new ArrayObject();
}
}
// object must be an embedded subject
else {
// add property statement
$this->_addStatement($entries, (object)array(
's' => $s, 'p' => $p, 'o' => (object)array(
'@id' => $o->{'@id'})));
// recurse into subject
$this->_getStatements($o, $namer, $bnodes, $subjects);
}
}
}
}
}
/**
* Converts a @list value into an embedded linked list of blank nodes in
* expanded form. The resulting array can be used as an RDF-replacement for
* a property that used a @list.
*
* @param array $value the @list value.
*
* @return stdClass the head of the linked list of blank nodes.
*/
protected function _makeLinkedList($value) {
// convert @list array into embedded blank node linked list
$list = $value->{'@list'};
// build linked list in reverse
$len = count($list);
$tail = (object)array('@id' => self::RDF_NIL);
for($i = $len - 1; $i >= 0; --$i) {
$tail = (object)array(
self::RDF_FIRST => array($list[$i]),
self::RDF_REST => array($tail));
}
return $tail;
}
/**
* Adds a statement to an array of statements. If the statement already exists
* in the array, it will not be added.
*
* @param ArrayObject $statements the statements array.
* @param stdClass $statement the statement to add.
*/
protected function _addStatement($statements, $statement) {
foreach($statements as $s) {
if($s->s === $statement->s && $s->p === $statement->p &&
self::compareValues($s->o, $statement->o)) {
return;
}
}
$statements[] = $statement;
}
/**
* Hashes all of the statements about a blank node.
*
* @param ArrayObject $statements the statements about the bnode.
* @param UniqueNamer $namer the canonical bnode namer.
*
* @return string the new hash.
*/
protected function _hashStatements($statements, $namer) {
// serialize all statements
$triples = array();
foreach($statements as $statement) {
// serialize triple
$triple = '';
// serialize subject
if($statement->s === '_:a') {
$triple .= '_:a';
}
else if(strpos($statement->s, '_:') === 0) {
$id = $statement->s;
$id = $namer->isNamed($id) ? $namer->getName($id) : '_:z';
$triple .= $id;
}
else {
$triple .= '<' . $statement->s . '>';
}
// serialize property
$p = ($statement->p === '@type') ? self::RDF_TYPE : $statement->p;
$triple .= ' <' . $p . '> ';
// serialize object
if(self::_isBlankNode($statement->o)) {
if($statement->o->{'@id'} === '_:a') {
$triple .= '_:a';
}
else {
$id = $statement->o->{'@id'};
$id = $namer->isNamed($id) ? $namer->getName($id) : '_:z';
$triple .= $id;
}
}
else if(is_string($statement->o)) {
$triple .= '"' . $statement->o . '"';
}
else if(self::_isSubjectReference($statement->o)) {
$triple .= '<' . $statement->o->{'@id'} . '>';
}
// must be a value
else {
$triple .= '"' . $statement->o->{'@value'} . '"';
if(property_exists($statement->o, '@type')) {
$triple .= '^^<' . $statement->o->{'@type'} . '>';
}
else if(property_exists($statement->o, '@language')) {
$triple .= '@' . $statement->o{'@language'};
}
}
// add triple
$triples[] = $triple;
}
// sort serialized triples
sort($triples);
// return hashed triples
return sha1(implode($triples));
}
/**
* Produces a hash for the paths of adjacent bnodes for a bnode,
* incorporating all information about its subgraph of bnodes. This
* method will recursively pick adjacent bnode permutations that produce the
* lexicographically-least 'path' serializations.
*
* @param stdClass $bnodes the map of bnode statements.
* @param ArrayObject $statements the statements for the bnode to produce
* the hash for.
* @param UniqueNamer $namer the canonical bnode namer.
* @param UniqueNamer $path_namer the namer used to assign names to adjacent
* bnodes.
*
* @return stdClass the hash and path namer used.
*/
protected function _hashPaths($bnodes, $statements, $namer, $path_namer) {
// create SHA-1 digest
$md = hash_init('sha1');
// group adjacent bnodes by hash, keep properties and references separate
$groups = new stdClass();
$cache = new stdClass();
foreach($statements as $statement) {
if($statement->s !== '_:a' && strpos($statement->s, '_:') === 0) {
$bnode = $statement->s;
$direction = 'p';
}
else {
$bnode = $this->_getBlankNodeName($statement->o);
$direction = 'r';
}
if($bnode !== null) {
// get bnode name (try canonical, path, then hash)
if($namer->isNamed($bnode)) {
$name = $namer->getName($bnode);
}
else if($path_namer->isNamed($bnode)) {
$name = $path_namer->getName($bnode);
}
else if(property_exists($cache, $bnode)) {
$name = $cache->{$bnode};
}
else {
$name = $this->_hashStatements($bnodes->{$bnode}, $namer);
$cache->{$bnode} = $name;
}
// hash direction, property, and bnode name/hash
$group_md = hash_init('sha1');
hash_update($group_md, $direction);
hash_update($group_md,
($statement->p === '@type') ? self::RDF_TYPE : $statement->p);
hash_update($group_md, $name);
$group_hash = hash_final($group_md);
// add bnode to hash group
if(property_exists($groups, $group_hash)) {
$groups->{$group_hash}[] = $bnode;
}
else {
$groups->{$group_hash} = array($bnode);
}
}
}
// iterate over groups in sorted hash order
$group_hashes = array_keys((array)$groups);
sort($group_hashes);
foreach($group_hashes as $group_hash) {
// digest group hash
hash_update($md, $group_hash);
// choose a path and namer from the permutations
$chosen_path = null;
$chosen_namer = null;
$permutator = new Permutator($groups->{$group_hash});
while($permutator->hasNext()) {
$permutation = $permutator->next();
$path_namer_copy = clone $path_namer;
// build adjacent path
$path = '';
$skipped = false;
$recurse = array();
foreach($permutation as $bnode) {
// use canonical name if available
if($namer->isNamed($bnode)) {
$path .= $namer->getName($bnode);
}
else {
// recurse if bnode isn't named in the path yet
if(!$path_namer_copy->isNamed($bnode)) {
$recurse[] = $bnode;
}
$path .= $path_namer_copy->getName($bnode);
}
// skip permutation if path is already >= chosen path
if($chosen_path !== null && strlen($path) >= strlen($chosen_path) &&
$path > $chosen_path) {
$skipped = true;
break;
}
}
// recurse
if(!$skipped) {
foreach($recurse as $bnode) {
$result = $this->_hashPaths(
$bnodes, $bnodes->{$bnode}, $namer, $path_namer_copy);
$path .= $path_namer_copy->getName($bnode);
$path .= "<{$result->hash}>";
$path_namer_copy = $result->pathNamer;
// skip permutation if path is already >= chosen path
if($chosen_path !== null && strlen($path) >= strlen($chosen_path) &&
$path > $chosen_path) {
$skipped = true;
break;
}
}
}
if(!$skipped && ($chosen_path === null || $path < $chosen_path)) {
$chosen_path = $path;
$chosen_namer = $path_namer_copy;
}
}
// digest chosen path and update namer
hash_update($md, $chosen_path);
$path_namer = $chosen_namer;
}
// return SHA-1 hash and path namer
return (object)array(
'hash' => hash_final($md), 'pathNamer' => $path_namer);
}
/**
* A helper function that gets the blank node name from a statement value
* (a subject or object). If the statement value is not a blank node or it
* has an @id of '_:a', then null will be returned.
*
* @param mixed $value the statement value.
*
* @return mixed the blank node name or null if none was found.
*/
protected function _getBlankNodeName($value) {
return ((self::_isBlankNode($value) && $value->{'@id'} !== '_:a') ?
$value->{'@id'} : null);
}
/**
* Recursively flattens the subjects in the given JSON-LD expanded input.
*
* @param stdClass $subjects a map of subject @id to subject.
* @param mixed $input the JSON-LD expanded input.
* @param UniqueNamer $namer the blank node namer.
* @param mixed $name the name assigned to the current input if it is a bnode.
* @param mixed $list the list to append to, null for none.
*/
protected function _flatten($subjects, $input, $namer, $name, $list) {
// recurse through array
if(is_array($input)) {
foreach($input as $e) {
$this->_flatten($subjects, $e, $namer, null, $list);
}
}
// handle subject
else if(is_object($input)) {
// add value to list
if(self::_isValue($input) && $list) {
$list[] = $input;
return;
}
// get name for subject
if($name === null) {
if(property_exists($input, '@id')) {
$name = $input->{'@id'};
}
if(self::_isBlankNode($input)) {
$name = $namer->getName($name);
}
}
// add subject reference to list
if($list !== null) {
$list[] = (object)array('@id' => $name);
}
// create new subject or merge into existing one
if(property_exists($subjects, $name)) {
$subject = $subjects->{$name};
}
else {
$subject = $subjects->{$name} = new stdClass();
}
$subject->{'@id'} = $name;
foreach($input as $prop => $objects) {
// skip @id
if($prop === '@id') {
continue;
}
// copy keywords
if(self::_isKeyword($prop)) {
$subject->{$prop} = $objects;
continue;
}
// iterate over objects
foreach($objects as $o) {
// handle embedded subject or subject reference
if(self::_isSubject($o) || self::_isSubjectReference($o)) {
// rename blank node @id
$id = property_exists($o, '@id') ? $o->{'@id'} : '_:';
if(strpos($id, '_:') === 0) {
$id = $namer->getName($id);
}
// add reference and recurse
self::addValue($subject, $prop, (object)array('@id' => $id), true);
$this->_flatten($subjects, $o, $namer, $id, null);
}
else {
// recurse into list
if(self::_isListValue($o)) {
$l = new ArrayObject();
$this->_flatten($subjects, $o->{'@list'}, $namer, $name, $l);
$o = (object)array('@list' => (array)$l);
}
// add non-subject
self::addValue($subject, $prop, $o, true);
}
}
}
}
// add non-object to list
else if($list !== null) {
$list[] = $input;
}
}
/**
* Frames subjects according to the given frame.
*
* @param stdClass $state the current framing state.
* @param array $subjects the subjects to filter.
* @param array $frame the frame.
* @param mixed $parent the parent subject or top-level array.
* @param mixed $property the parent property, initialized to null.
*/
protected function _match_frame(
$state, $subjects, $frame, $parent, $property) {
// validate the frame
$this->_validateFrame($state, $frame);
$frame = $frame[0];
// filter out subjects that match the frame
$matches = $this->_filterSubjects($state, $subjects, $frame);
// get flags for current frame
$options = $state->options;
$embed_on = $this->_getFrameFlag($frame, $options, 'embed');
$explicit_on = $this->_getFrameFlag($frame, $options, 'explicit');
// add matches to output
foreach($matches as $id => $subject) {
/* Note: In order to treat each top-level match as a compartmentalized
result, create an independent copy of the embedded subjects map when the
property is null, which only occurs at the top-level. */
if($property === null) {
$state->embeds = new stdClass();
}
// start output
$output = new stdClass();
$output->{'@id'} = $id;
// prepare embed meta info
$embed = (object)array('parent' => $parent, 'property' => $property);
// if embed is on and there is an existing embed
if($embed_on && property_exists($state->embeds, $id)) {
// only overwrite an existing embed if it has already been added to its
// parent -- otherwise its parent is somewhere up the tree from this
// embed and the embed would occur twice once the tree is added
$embed_on = false;
// existing embed's parent is an array
$existing = $state->embeds->{$id};
if(is_array($existing->parent)) {
foreach($existing->parent as $p) {
if(self::compareValues($output, $p)) {
$embed_on = true;
break;
}
}
}
// existing embed's parent is an object
else if(self::hasValue(
$existing->parent, $existing->property, $output)) {
$embed_on = true;
}
// existing embed has already been added, so allow an overwrite
if($embed_on) {
$this->_removeEmbed($state, $id);
}
}
// not embedding, add output without any other properties
if(!$embed_on) {
$this->_addFrameOutput($state, $parent, $property, $output);
}
else {
// add embed meta info
$state->embeds->{$id} = $embed;
// iterate over subject properties
$props = array_keys((array)$subject);
sort($props);
foreach($props as $prop) {
// copy keywords to output
if(self::_isKeyword($prop)) {
$output->{$prop} = self::copy($subject->{$prop});
continue;
}
// if property isn't in the frame
if(!property_exists($frame, $prop)) {
// if explicit is off, embed values
if(!$explicit_on) {
$this->_embedValues($state, $subject, $prop, $output);
}
continue;
}
// add objects
$objects = $subject->{$prop};
foreach($objects as $o) {
// recurse into list
if(self::_isListValue($o)) {
// add empty list
$list = (object)array('@list' => array());
$this->_addFrameOutput($state, $output, $prop, $list);
// add list objects
$src = $o->{'@list'};
foreach($src as $o) {
// recurse into subject reference
if(self::_isSubjectReference($o)) {
$this->_match_frame(
$state, array($o->{'@id'}), $frame->{$prop},
$list, '@list');
}
// include other values automatically
else {
$this->_addFrameOutput(
$state, $list, '@list', self::copy($o));
}
}
continue;
}
// recurse into subject reference
if(self::_isSubjectReference($o)) {
$this->_match_frame(
$state, array($o->{'@id'}), $frame->{$prop}, $output, $prop);
}
// include other values automatically
else {
$this->_addFrameOutput($state, $output, $prop, self::copy($o));
}
}
}
// handle defaults
$props = array_keys((array)$frame);
sort($props);
foreach($props as $prop) {
// skip keywords
if(self::_isKeyword($prop)) {
continue;
}
// if omit default is off, then include default values for properties
// that appear in the next frame but are not in the matching subject
$next = $frame->{$prop}[0];
$omit_default_on = $this->_getFrameFlag(
$next, $options, 'omitDefault');
if(!$omit_default_on && !property_exists($output, $prop)) {
$preserve = '@null';
if(property_exists($next, '@default')) {
$preserve = self::copy($next->{'@default'});
}
$output->{$prop} = (object)array('@preserve' => $preserve);
}
}
// add output to parent
$this->_addFrameOutput($state, $parent, $property, $output);
}
}
}
/**
* Gets the frame flag value for the given flag name.
*
* @param stdClass $frame the frame.
* @param stdClass $options the framing options.
* @param string $name the flag name.
*
* @return mixed $the flag value.
*/
protected function _getFrameFlag($frame, $options, $name) {
$flag = "@$name";
return (property_exists($frame, $flag) ?
$frame->{$flag}[0] : $options[$name]);
}
/**
* Validates a JSON-LD frame, throwing an exception if the frame is invalid.
*
* @param stdClass $state the current frame state.
* @param array $frame the frame to validate.
*/
protected function _validateFrame($state, $frame) {
if(!is_array($frame) || count($frame) !== 1 || !is_object($frame[0])) {
throw new JsonLdException(
'Invalid JSON-LD syntax; a JSON-LD frame must be a single object.',
'jsonld.SyntaxError', array('frame' => $frame));
}
}
/**
* Returns a map of all of the subjects that match a parsed frame.
*
* @param stdClass $state the current framing state.
* @param array $subjects the set of subjects to filter.
* @param stdClass $frame the parsed frame.
*
* @return stdClass all of the matched subjects.
*/
protected function _filterSubjects($state, $subjects, $frame) {
$rval = new stdClass();
sort($subjects);
foreach($subjects as $id) {
$subject = $state->subjects->{$id};
if($this->_filterSubject($subject, $frame)) {
$rval->{$id} = $subject;
}
}
return $rval;
}
/**
* Returns true if the given subject matches the given frame.
*
* @param stdClass $subject the subject to check.
* @param stdClass $frame the frame to check.
*
* @return bool true if the subject matches, false if not.
*/
protected function _filterSubject($subject, $frame) {
// check @type (object value means 'any' type, fall through to ducktyping)
if(property_exists($frame, '@type') &&
!(count($frame->{'@type'}) === 1 && is_object($frame->{'@type'}[0]))) {
$types = $frame->{'@type'};
foreach($types as $type) {
// any matching @type is a match
if(self::hasValue($subject, '@type', $type)) {
return true;
}
}
return false;
}
// check ducktype
foreach($frame as $k => $v) {
// only not a duck if @id or non-keyword isn't in subject
if(($k === '@id' || !self::_isKeyword($k)) &&
!property_exists($subject, $k)) {
return false;
}
}
return true;
}
/**
* Embeds values for the given subject and property into the given output
* during the framing algorithm.
*
* @param stdClass $state the current framing state.
* @param stdClass $subject the subject.
* @param string $property the property.
* @param mixed $output the output.
*/
protected function _embedValues($state, $subject, $property, $output) {
// embed subject properties in output
$objects = $subject->{$property};
foreach($objects as $o) {
// recurse into @list
if(self::_isListValue($o)) {
$list = (object)array('@list' => new ArrayObject());
$this->_addFrameOutput($state, $output, $property, $list);
$this->_embedValues($state, $o, '@list', $list->{'@list'});
$list->{'@list'} = (array)$list->{'@list'};
return;
}
// handle subject reference
if(self::_isSubjectReference($o)) {
$id = $o->{'@id'};
// embed full subject if isn't already embedded
if(!property_exists($state->embeds, $id)) {
// add embed
$embed = (object)array('parent' => $output, 'property' => $property);
$state->embeds->{$id} = $embed;
// recurse into subject
$o = new stdClass();
$s = $state->subjects->{$id};
foreach($s as $prop => $v) {
// copy keywords
if(self::_isKeyword($prop)) {
$o->{$prop} = self::copy($v);
continue;
}
$this->_embedValues($state, $s, $prop, $o);
}
}
$this->_addFrameOutput($state, $output, $property, $o);
}
// copy non-subject value
else {
$this->_addFrameOutput($state, $output, $property, self::copy($o));
}
}
}
/**
* Removes an existing embed.
*
* @param stdClass $state the current framing state.
* @param string $id the @id of the embed to remove.
*/
protected function _removeEmbed($state, $id) {
// get existing embed
$embeds = $state->embeds;
$embed = $embeds->{$id};
$property = $embed->property;
// create reference to replace embed
$subject = (object)array('@id' => id);
// remove existing embed
if(is_array($embed->parent)) {
// replace subject with reference
foreach($embed->parent as $i => $parent) {
if(self::compareValues($parent, $subject)) {
$embed->parent[$i] = $subject;
break;
}
}
}
else {
// replace subject with reference
$useArray = is_array($embed->parent->{$property});
self::removeValue($embed->parent, $property, $subject, $useArray);
self::addValue($embed->parent, $property, $subject, $useArray);
}
// recursively remove dependent dangling embeds
$removeDependents = function($id) {
// get embed keys as a separate array to enable deleting keys in map
$ids = array_keys((array)$embeds);
foreach($ids as $next) {
if(property_exists($embeds, $next) &&
is_object($embeds->{$next}->parent) &&
$embeds->{$next}->parent->{'@id'} === $id) {
unset($embeds->{$next});
$removeDependents($next);
}
}
};
$removeDependents($id);
}
/**
* Adds framing output to the given parent.
*
* @param stdClass $state the current framing state.
* @param mixed $parent the parent to add to.
* @param string $property the parent property.
* @param mixed $output the output to add.
*/
protected function _addFrameOutput($state, $parent, $property, $output) {
if(is_object($parent) && !($parent instanceof ArrayObject)) {
self::addValue($parent, $property, $output, true);
}
else {
$parent[] = $output;
}
}
/**
* Removes the @preserve keywords as the last step of the framing algorithm.
*
* @param stdClass $ctx the active context used to compact the input.
* @param mixed $input the framed, compacted output.
*
* @return mixed the resulting output.
*/
protected function _removePreserve($ctx, $input) {
// recurse through arrays
if(is_array($input)) {
$output = array();
foreach($input as $e) {
$result = $this->_removePreserve($ctx, $e);
// drop nulls from arrays
if($result !== null) {
$output[] = $result;
}
}
$input = $output;
}
else if(is_object($input)) {
// remove @preserve
if(property_exists($input, '@preserve')) {
if($input->{'@preserve'} === '@null') {
return null;
}
return $input->{'@preserve'};
}
// skip @values
if(self::_isValue($input)) {
return $input;
}
// recurse through @lists
if(self::_isListValue($input)) {
$input->{'@list'} = $this->_removePreserve($ctx, $input->{'@list'});
return $input;
}
// recurse through properties
foreach($input as $prop => $v) {
$result = $this->_removePreserve($ctx, $v);
$container = self::getContextValue($ctx, $prop, '@container');
if(is_array($result) && count($result) === 1 &&
$container !== '@set' && $container !== '@list') {
$result = $result[0];
}
$input->{$prop} = $result;
}
}
return $input;
}
/**
* Compares two strings first based on length and then lexicographically.
*
* @param string $a the first string.
* @param string $b the second string.
*
* @return integer -1 if a < b, 1 if a > b, 0 if a == b.
*/
protected function _compareShortestLeast($a, $b) {
if(strlen($a) < strlen($b)) {
return -1;
}
else if(strlen($b) < strlen($a)) {
return 1;
}
return ($a < $b) ? -1 : (($a > $b) ? 1 : 0);
}
/**
* Ranks a term that is possible choice for compacting an IRI associated with
* the given value.
*
* @param stdClass $ctx the active context.
* @param string $term the term to rank.
* @param mixed $value the associated value.
*
* @return integer the term rank.
*/
protected function _rankTerm($ctx, $term, $value) {
// no term restrictions for a null value
if($value === null) {
return 3;
}
// get context entry for term
$entry = $ctx->mappings->{$term};
$has_type = property_exists($entry, '@type');
$has_language = property_exists($entry, '@language');
$has_default_language = property_exists($ctx, '@language');
// @list rank is the sum of its values' ranks
if(self::_isListValue($value)) {
$list = $value->{'@list'};
if(count($list) === 0) {
return ($entry->{'@container'} === '@list') ? 1 : 0;
}
// sum term ranks for each list value
$sum = 0;
foreach($list as $v) {
$sum += $this->_rankTerm($ctx, $term, $v);
}
return $sum;
}
// rank boolean or number
if(is_bool($value) || is_double($value) || is_integer($value)) {
if(is_bool($value)) {
$type = self::XSD_BOOLEAN;
}
else if(is_double($value)) {
$type = self::XSD_DOUBLE;
}
else {
$type = self::XSD_INTEGER;
}
if($has_type && $entry->{'@type'} === $type) {
return 3;
}
return (!$has_type && !$has_language) ? 2 : 1;
}
// rank string (this means the value has no @language)
if(is_string($value)) {
// entry @language is specifically null or no @type, @language, or default
if(($has_language && $entry->{'@language'} === null) ||
(!$has_type && !$has_language && !$has_default_language)) {
return 3;
}
return 0;
}
// Note: Value must be an object that is a @value or subject/reference.
// @value must have either @type or @language
if(self::_isValue($value)) {
if(property_exists($value, '@type')) {
// @types match
if($has_type && $value->{'@type'} === $entry->{'@type'}) {
return 3;
}
return (!$has_type && !$has_language) ? 1 : 0;
}
// @languages match or entry has no @type or @language but default
// @language matches
if(($has_language && $value->{'@language'} === $entry->{'@language'}) ||
(!$has_type && !$has_language && $has_default_language &&
$value->{'@language'} === $ctx->{'@language'})) {
return 3;
}
return (!$has_type && !$has_language) ? 1 : 0;
}
// value must be a subject/reference
if($has_type && $entry->{'@type'} === '@id') {
return 3;
}
return (!$has_type && !$has_language) ? 1 : 0;
}
/**
* Compacts an IRI or keyword into a term or prefix if it can be. If the
* IRI has an associated value it may be passed.
*
* @param stdClass $ctx the active context to use.
* @param string $iri the IRI to compact.
* @param mixed $value the value to check or null.
*
* @return string the compacted term, prefix, keyword alias, or original IRI.
*/
protected function _compactIri($ctx, $iri, $value=null) {
// can't compact null
if($iri === null) {
return $iri;
}
// compact rdf:type
if($iri === self::RDF_TYPE) {
return '@type';
}
// term is a keyword
if(self::_isKeyword($iri)) {
// return alias if available
$aliases = $ctx->keywords->{$iri};
if(count($aliases) > 0) {
return $aliases[0];
}
else {
// no alias, keep original keyword
return $iri;
}
}
// find all possible term matches
$terms = array();
$highest = 0;
$listContainer = false;
$isList = self::_isListValue($value);
foreach($ctx->mappings as $term => $entry) {
$has_container = property_exists($entry, '@container');
// skip terms with non-matching iris
if($entry->{'@id'} !== $iri) {
continue;
}
// skip @set containers for @lists
if($isList && $has_container && $entry->{'@container'} === '@set') {
continue;
}
// skip @list containers for non-@lists
if(!$isList && $has_container && $entry->{'@container'} === '@list') {
continue;
}
// for @lists, if listContainer is set, skip non-list containers
if($isList && $listContainer && (!$has_container ||
$entry->{'@container'} !== '@list')) {
continue;
}
// rank term
$rank = $this->_rankTerm($ctx, $term, $value);
if($rank > 0) {
// add 1 to rank if container is a @set
if($has_container && $entry->{'@container'} === '@set') {
$rank += 1;
}
// for @lists, give preference to @list containers
if($isList && !$listContainer && $has_container &&
$entry->{'@container'} === '@list') {
$listContainer = true;
$terms = array();
$highest = $rank;
$terms[] = $term;
}
// only push match if rank meets current threshold
else if($rank >= $highest) {
if($rank > $highest) {
$terms = array();
$highest = $rank;
}
$terms[] = $term;
}
}
}
// no term matches, add possible CURIEs
if(count($terms) === 0) {
foreach($ctx->mappings as $term => $entry) {
// skip terms with colons, they can't be prefixes
if(strpos($term, ':') !== false) {
continue;
}
// skip entries with @ids that are not partial matches
if($entry->{'@id'} === $iri || strpos($iri, $entry->{'@id'}) !== 0) {
continue;
}
// add CURIE as term if it has no mapping
$curie = $term . ':' . substr($iri, strlen($entry->{'@id'}));
if(!property_exists($ctx->mappings, $curie)) {
$terms[] = $curie;
}
}
}
// no matching terms, use IRI
if(count($terms) === 0) {
return $iri;
}
// return shortest and lexicographically-least term
usort($terms, array($this, '_compareShortestLeast'));
return $terms[0];
}
/**
* Defines a context mapping during context processing.
*
* @param stdClass $active_ctx the current active context.
* @param stdClass $ctx the local context being processed.
* @param string $key the key in the local context to define the mapping for.
* @param string $base the base IRI.
* @param stdClass $defined a map of defining/defined keys to detect cycles
* and prevent double definitions.
*/
protected function _defineContextMapping(
$active_ctx, $ctx, $key, $base, $defined) {
if(property_exists($defined, $key)) {
// key already defined
if($defined->{$key}) {
return;
}
// cycle detected
throw new JsonLdException(
'Cyclical context definition detected.',
'jsonld.CyclicalContext',
(object)array('context' => $ctx, 'key' => $key));
}
// now defining key
$defined->{$key} = false;
// if key has a prefix, define it first
$colon = strpos($key, ':');
$prefix = null;
if($colon !== false) {
$prefix = substr($key, 0, $colon);
if(property_exists($ctx, $prefix)) {
// define parent prefix
$this->_defineContextMapping(
$active_ctx, $ctx, $prefix, $base, $defined);
}
}
// get context key value
$value = $ctx->{$key};
if(self::_isKeyword($key)) {
// only @language is permitted
if($key !== '@language') {
throw new JsonLdException(
'Invalid JSON-LD syntax; keywords cannot be overridden.',
'jsonld.SyntaxError', array('context' => $ctx));
}
if($value !== null && !is_string($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; the value of "@language" in a ' +
'@context must be a string or null.',
'jsonld.SyntaxError', array('context' => $ctx));
}
if($value === null) {
unset($active_ctx->{'@language'});
}
else {
$active_ctx->{'@language'} = $value;
}
$defined->{$key} = true;
return;
}
// clear context entry
if($value === null) {
if(property_exists($active_ctx->mappings, $key)) {
// if key is a keyword alias, remove it
$kw = $active_ctx->mappings->{$key}->{'@id'};
if(self::_isKeyword($kw)) {
array_splice($active_ctx->keywords->{$kw},
in_array($key, $active_ctx->keywords->{$kw}), 1);
}
unset($active_ctx->mappings->{$key});
}
$defined->{$key} = true;
return;
}
if(is_string($value)) {
if(self::_isKeyword($value)) {
// disallow aliasing @context and @preserve
if($value === '@context' || $value === '@preserve') {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context and @preserve cannot be aliased.',
'jsonld.SyntaxError');
}
// uniquely add key as a keyword alias and resort
$aliases = $active_ctx->keywords->{$value};
if(in_array($key, $active_ctx->keywords->{$value}) === false) {
$active_ctx->keywords->{$value}[] = $key;
usort($active_ctx->keywords->{$value},
array($this, '_compareShortestLeast'));
}
}
else {
// expand value to a full IRI
$value = $this->_expandContextIri(
$active_ctx, $ctx, $value, $base, $defined);
}
// define/redefine key to expanded IRI/keyword
$active_ctx->mappings->{$key} = (object)array('@id' => $value);
$defined->{$key} = true;
return;
}
if(!is_object($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context property values must be ' +
'strings or objects.',
'jsonld.SyntaxError', array('context' => $ctx));
}
// create new mapping
$mapping = new stdClass();
if(property_exists($value, '@id')) {
$id = $value->{'@id'};
if(!is_string($id)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context @id values must be strings.',
'jsonld.SyntaxError', array('context' => $ctx));
}
// expand @id to full IRI
$id = $this->_expandContextIri($active_ctx, $ctx, $id, $base, $defined);
// add @id to mapping
$mapping->{'@id'} = $id;
}
else {
// non-IRIs *must* define @ids
if($prefix === null) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context terms must define an @id.',
'jsonld.SyntaxError', array('context' => $ctx, 'key' => $key));
}
// set @id based on prefix parent
if(property_exists($active_ctx->mappings, $prefix)) {
$suffix = substr($key, $colon + 1);
$mapping->{'@id'} = $active_ctx->mappings->{$prefix}->{'@id'} . $suffix;
}
// key is an absolute IRI
else {
$mapping->{'@id'} = $key;
}
}
if(property_exists($value, '@type')) {
$type = $value->{'@type'};
if(!is_string($type)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context @type values must be strings.',
'jsonld.SyntaxError', array('context' => $ctx));
}
if($type !== '@id') {
// expand @type to full IRI
$type = $this->_expandContextIri(
$active_ctx, $ctx, $type, '', $defined);
}
// add @type to mapping
$mapping->{'@type'} = $type;
}
if(property_exists($value, '@container')) {
$container = $value->{'@container'};
if($container !== '@list' && $container !== '@set') {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context @container value must be ' +
'"@list" or "@set".',
'jsonld.SyntaxError', array('context' => $ctx));
}
// add @container to mapping
$mapping->{'@container'} = $container;
}
if(property_exists($value, '@language') &&
!property_exists($value, '@type')) {
$language = $value->{'@language'};
if($language !== null && !is_string($language)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; @context @language value must be ' +
'a string or null.',
'jsonld.SyntaxError', array('context' => $ctx));
}
// add @language to mapping
$mapping->{'@language'} = $language;
}
// merge onto parent mapping if one exists for a prefix
if($prefix !== null && property_exists($active_ctx->mappings, $prefix)) {
$child = $mapping;
$mapping = self::copy($active_ctx->mappings->{$prefix});
foreach($child as $k => $v) {
$mapping->{$k} = $v;
}
}
// define key mapping
$active_ctx->mappings->{$key} = $mapping;
$defined->{$key} = true;
}
/**
* Expands a string value to a full IRI during context processing. It can
* be assumed that the value is not a keyword.
*
* @param stdClass $active_ctx the current active context.
* @param stdClass $ctx the local context being processed.
* @param string $value the string value to expand.
* @param string $base the base IRI.
* @param stdClass $defined a map for tracking cycles in context definitions.
*
* @return mixed the expanded value.
*/
protected function _expandContextIri(
$active_ctx, $ctx, $value, $base, $defined) {
// dependency not defined, define it
if(property_exists($ctx, $value) &&
(!property_exists($defined, $value) || !$defined->{$value})) {
$this->_defineContextMapping($active_ctx, $ctx, $value, $base, $defined);
}
// recurse if value is a term
if(property_exists($active_ctx->mappings, $value)) {
$id = $active_ctx->mappings->{$value}->{'@id'};
// value is already an absolute IRI
if($value === $id) {
return $value;
}
return $this->_expandContextIri($active_ctx, $ctx, $id, $base, $defined);
}
// split value into prefix:suffix
if(strpos($value, ':') !== false) {
list($prefix, $suffix) = explode(':', $value, 2);
// a prefix of '_' indicates a blank node
if($prefix === '_') {
return $value;
}
// a suffix of '//' indicates value is an absolute IRI
if(strpos($suffix, '//') === 0) {
return $value;
}
// dependency not defined, define it
if(property_exists($ctx, $prefix) &&
(!property_exists($defined, $prefix) || !$defined->{$prefix})) {
$this->_defineContextMapping(
$active_ctx, $ctx, $prefix, $base, $defined);
}
// recurse if prefix is defined
if(property_exists($active_ctx->mappings, $prefix)) {
$id = $active_ctx->mappings->{$prefix}->{'@id'};
return $this->_expandContextIri(
$active_ctx, $ctx, $id, $base, $defined) . $suffix;
}
// consider value an absolute IRI
return $value;
}
// prepend base
$value = "$base$value";
// value must now be an absolute IRI
if(!self::_isAbsoluteIri($value)) {
throw new JsonLdException(
'Invalid JSON-LD syntax; a @context value does not expand to ' +
'an absolute IRI.',
'jsonld.SyntaxError', array('context' => $ctx, 'value' => $value));
}
return $value;
}
/**
* Expands a term into an absolute IRI. The term may be a regular term, a
* prefix, a relative IRI, or an absolute IRI. In any case, the associated
* absolute IRI will be returned.
*
* @param stdClass $ctx the active context to use.
* @param string $term the term to expand.
* @param string $base the base IRI to use if a relative IRI is detected.
*
* @return string the expanded term as an absolute IRI.
*/
protected function _expandTerm($ctx, $term, $base='') {
// nothing to expand
if($term === null) {
return null;
}
// the term has a mapping, so it is a plain term
if(property_exists($ctx->mappings, $term)) {
$id = $ctx->mappings->{$term}->{'@id'};
// term is already an absolute IRI
if($term === $id) {
return $term;
}
return $this->_expandTerm($ctx, $id, $base);
}
// split term into prefix:suffix
if(strpos($term, ':') !== false) {
list($prefix, $suffix) = explode(':', $term, 2);
// a prefix of '_' indicates a blank node
if($prefix === '_') {
return $term;
}
// a suffix of '//' indicates value is an absolute IRI
if(strpos($suffix, '//') === 0) {
return $term;
}
// the term's prefix has a mapping, so it is a CURIE
if(property_exists($ctx->mappings, $prefix)) {
return $this->_expandTerm(
$ctx, $ctx->mappings->{$prefix}->{'@id'}, $base) . $suffix;
}
// consider term an absolute IRI
return $term;
}
// prepend base to term
return "$base$term";
}
/**
* Resolves external @context URLs using the given URL resolver. Each instance
* of @context in the input that refers to a URL will be replaced with the
* JSON @context found at that URL.
*
* @param mixed $input the JSON-LD object with possible contexts.
* @param callable $resolver(url, callback(err, jsonCtx)) the URL resolver.
*
* @return mixed the result.
*/
protected function _resolveUrls($input, $resolver) {
// keeps track of resolved URLs (prevents duplicate work)
$urls = new stdClass();
// finds URLs in @context properties and replaces them with their
// resolved @contexts if replace is true
$findUrls = function($input, $replace) use (&$findUrls, $urls) {
if(is_array($input)) {
$output = array();
foreach($input as $v) {
$output[] = $findUrls($v, $replace);
}
return $output;
}
else if(is_object($input)) {
foreach($input as $k => $v) {
if($k !== '@context') {
$input->{$k} = $findUrls($v, $replace);
continue;
}
// array @context
if(is_array($v)) {
foreach($v as $i => $url) {
if(is_string($url)) {
// replace w/resolved @context if requested
if($replace) {
$v[$i] = $urls->{$url};
}
// unresolved @context found
else if(!property_exists($urls, $url)) {
$urls->{$url} = new stdClass();
}
}
}
}
// string @context
else if(is_string($v)) {
// replace w/resolved @context if requested
if($replace) {
$input->{$key} = $urls->{$v};
}
// unresolved @context found
else if(!property_exists($urls, $v)) {
$urls->{$v} = new stdClass();
}
}
}
}
return $input;
};
$input = $findUrls($input, false);
// resolve all URLs
foreach($urls as $url => $v) {
// validate URL
if(filter_var($url, FILTER_VALIDATE_URL) === false) {
throw new JsonLdException(
'Malformed URL.', 'jsonld.InvalidUrl', array('url' => $url));
}
// resolve URL
$ctx = $resolver($url);
// parse string context as JSON
if(is_string($ctx)) {
$ctx = json_decode($ctx);
switch(json_last_error()) {
case JSON_ERROR_NONE:
break;
case JSON_ERROR_DEPTH:
throw new JsonLdException(
'Could not parse JSON from URL; the maximum stack depth has ' .
'been exceeded.', 'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_STATE_MISMATCH:
throw new JsonLdException(
'Could not parse JSON from URL; invalid or malformed JSON.',
'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_CTRL_CHAR:
case JSON_ERROR_SYNTAX:
throw new JsonLdException(
'Could not parse JSON from URL; syntax error, malformed JSON.',
'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_UTF8:
throw new JsonLdException(
'Could not parse JSON from URL; malformed UTF-8 characters.',
'jsonld.ParseError', array('url' => $url));
default:
throw new JsonLdException(
'Could not parse JSON from URL; unknown error.',
'jsonld.ParseError', array('url' => $url));
}
}
// ensure ctx is an object
if(!is_object($ctx)) {
throw new JsonLdException(
'URL does not resolve to a valid JSON-LD object.',
'jsonld.InvalidUrl', array('url' => $url));
}
// FIXME: needs to recurse to resolve URLs in the result, and
// detect cycles, and limit recursion
if(property_exists($ctx, '@context')) {
$urls->{$url} = $ctx->{'@context'};
}
}
// do url replacement
return $findUrls($input, true);
}
/**
* Gets the initial context.
*
* @return stdClass the initial context.
*/
protected function _getInitialContext() {
return (object)array(
'mappings' => new stdClass(),
'keywords' => (object)array(
'@context'=> array(),
'@container'=> array(),
'@default'=> array(),
'@embed'=> array(),
'@explicit'=> array(),
'@graph'=> array(),
'@id'=> array(),
'@language'=> array(),
'@list'=> array(),
'@omitDefault'=> array(),
'@preserve'=> array(),
'@set'=> array(),
'@type'=> array(),
'@value'=> array()
));
}
/**
* Returns whether or not the given value is a keyword (or a keyword alias).
*
* @param string $value the value to check.
* @param stdClass [$ctx] the active context to check against.
*
* @return bool true if the value is a keyword, false if not.
*/
protected static function _isKeyword($value, $ctx=null) {
if($ctx !== null) {
if(property_exists($ctx->keywords, $value)) {
return true;
}
foreach($ctx->keywords as $kw => $aliases) {
if(in_array($value, $aliases) !== false) {
return true;
}
}
}
else {
switch($value) {
case '@context':
case '@container':
case '@default':
case '@embed':
case '@explicit':
case '@graph':
case '@id':
case '@language':
case '@list':
case '@omitDefault':
case '@preserve':
case '@set':
case '@type':
case '@value':
return true;
}
}
return false;
}
/**
* Returns true if the given input is an empty Object.
*
* @param mixed $input the input to check.
*
* @return bool true if the input is an empty Object, false if not.
*/
protected static function _isEmptyObject($input) {
return is_object($input) && count(get_object_vars($input)) === 0;
}
/**
* Returns true if the given input is an Array of Strings.
*
* @param mixed $input the input to check.
*
* @return bool true if the input is an Array of Strings, false if not.
*/
protected static function _isArrayOfStrings($input) {
if(!is_array($input)) {
return false;
}
foreach($input as $v) {
if(!is_string($v)) {
return false;
}
}
return true;
}
/**
* Returns true if the given value is a subject with properties.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a subject with properties, false if not.
*/
protected static function _isSubject($value) {
$rval = false;
// Note: A value is a subject if all of these hold true:
// 1. It is an Object.
// 2. It is not a @value, @set, or @list.
// 3. It has more than 1 key OR any existing key is not @id.
if(is_object($value) &&
!property_exists($value, '@value') &&
!property_exists($value, '@set') &&
!property_exists($value, '@list')) {
$count = count(get_object_vars($value));
$rval = ($count > 1 || !property_exists($value, '@id'));
}
return $rval;
}
/**
* Returns true if the given value is a subject reference.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a subject reference, false if not.
*/
protected static function _isSubjectReference($value) {
// Note: A value is a subject reference if all of these hold true:
// 1. It is an Object.
// 2. It has a single key: @id.
return (is_object($value) && count(get_object_vars($value)) === 1 &&
property_exists($value, '@id'));
}
/**
* Returns true if the given value is a @value.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a @value, false if not.
*/
protected static function _isValue($value) {
// Note: A value is a @value if all of these hold true:
// 1. It is an Object.
// 2. It has the @value property.
return is_object($value) && property_exists($value, '@value');
}
/**
* Returns true if the given value is a @set.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a @set, false if not.
*/
protected static function _isSetValue($value) {
// Note: A value is a @set if all of these hold true:
// 1. It is an Object.
// 2. It has the @set property.
return is_object($value) && property_exists($value, '@set');
}
/**
* Returns true if the given value is a @list.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a @list, false if not.
*/
protected static function _isListValue($value) {
// Note: A value is a @list if all of these hold true:
// 1. It is an Object.
// 2. It has the @list property.
return is_object($value) && property_exists($value, '@list');
}
/**
* Returns true if the given value is a blank node.
*
* @param mixed $value the value to check.
*
* @return bool true if the value is a blank node, false if not.
*/
protected static function _isBlankNode($value) {
$rval = false;
// Note: A value is a blank node if all of these hold true:
// 1. It is an Object.
// 2. If it has an @id key its value begins with '_:'.
// 3. It has no keys OR is not a @value, @set, or @list.
if(is_object($value)) {
if(property_exists($value, '@id')) {
$rval = (strpos($value->{'@id'}, '_:') === 0);
}
else {
$rval = (count(get_object_vars($value)) === 0 ||
!(property_exists($value, '@value') ||
property_exists($value, '@set') ||
property_exists($value, '@list')));
}
}
return $rval;
}
/**
* Returns true if the given value is an absolute IRI, false if not.
*
* @param string $value the value to check.
*
* @return bool true if the value is an absolute IRI, false if not.
*/
protected static function _isAbsoluteIri($value) {
return strpos($value, ':') !== false;
}
}
/**
* A JSON-LD Exception.
*/
class JsonLdException extends Exception {
protected $type;
protected $details;
protected $cause;
public function __construct($msg, $type, $details=null, $previous=null) {
$this->type = $type;
$this->details = $details;
$this->cause = $previous;
parent::__construct($msg, 0, $previous);
}
public function __toString() {
$rval = __CLASS__ . ": [{$this->type}]: {$this->message}\n";
if($this->details) {
$rval .= 'details: ' . print_r($this->details, true) . "\n";
}
if($this->cause) {
$rval .= 'cause: ' . $this->cause;
}
$rval .= $this->getTraceAsString() . "\n";
return $rval;
}
};
/**
* A UniqueNamer issues unique names, keeping track of any previously issued
* names.
*/
class UniqueNamer {
/**
* Constructs a new UniqueNamer.
*
* @param prefix the prefix to use ('<prefix><counter>').
*/
public function __construct($prefix) {
$this->prefix = $prefix;
$this->counter = 0;
$this->existing = new stdClass();
$this->order = array();
}
/**
* Clones this UniqueNamer.
*/
public function __clone() {
$this->existing = clone $this->existing;
}
/**
* Gets the new name for the given old name, where if no old name is given
* a new name will be generated.
*
* @param mixed [$old_name] the old name to get the new name for.
*
* @return string the new name.
*/
public function getName($old_name=null) {
// return existing old name
if($old_name && property_exists($this->existing, $old_name)) {
return $this->existing->{$old_name};
}
// get next name
$name = $this->prefix . $this->counter;
$this->counter += 1;
// save mapping
if($old_name !== null) {
$this->existing->{$old_name} = $name;
$this->order[] = $old_name;
}
return $name;
}
/**
* Returns true if the given old name has already been assigned a new name.
*
* @param string $old_name the old name to check.
*
* @return true if the old name has been assigned a new name, false if not.
*/
public function isNamed($old_name) {
return property_exists($this->existing, $old_name);
}
}
/**
* A Permutator iterates over all possible permutations of the given array
* of elements.
*/
class Permutator {
/**
* Constructs a new Permutator.
*
* @param array $list the array of elements to iterate over.
*/
public function __construct($list) {
// original array
$this->list = $list;
sort($this->list);
// indicates whether there are more permutations
$this->done = false;
// directional info for permutation algorithm
$this->left = new stdClass();
foreach($list as $v) {
$this->left->{$v} = true;
}
}
/**
* Returns true if there is another permutation.
*
* @return bool true if there is another permutation, false if not.
*/
public function hasNext() {
return !$this->done;
}
/**
* Gets the next permutation. Call hasNext() to ensure there is another one
* first.
*
* @return array the next permutation.
*/
public function next() {
// copy current permutation
$rval = $this->list;
/* Calculate the next permutation using the Steinhaus-Johnson-Trotter
permutation algorithm. */
// get largest mobile element k
// (mobile: element is greater than the one it is looking at)
$k = null;
$pos = 0;
$length = count($this->list);
for($i = 0; $i < $length; ++$i) {
$element = $this->list[$i];
$left = $this->left->{$element};
if(($k === null || $element > $k) &&
(($left && $i > 0 && $element > $this->list[$i - 1]) ||
(!$left && $i < ($length - 1) && $element > $this->list[$i + 1]))) {
$k = $element;
$pos = $i;
}
}
// no more permutations
if($k === null) {
$this->done = true;
}
else {
// swap k and the element it is looking at
$swap = $this->left->{$k} ? $pos - 1 : $pos + 1;
$this->list[$pos] = $this->list[$swap];
$this->list[$swap] = $k;
// reverse the direction of all elements larger than k
for($i = 0; $i < $length; ++$i) {
if($this->list[$i] > $k) {
$this->left->{$this->list[$i]} = !$this->left->{$this->list[$i]};
}
}
}
return $rval;
}
}
/* end of file, omit ?> */