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Implement JSON-LD context URL resolution.

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This commit is contained in:
Dave Longley 2012-05-07 17:12:10 -04:00
parent 52fa975894
commit 4c847440c7
1 changed files with 238 additions and 143 deletions
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307
jsonld.php
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@ -45,7 +45,7 @@
* [strict] use strict mode (default: true). * [strict] use strict mode (default: true).
* [optimize] true to optimize the compaction (default: false). * [optimize] true to optimize the compaction (default: false).
* [graph] true to always output a top-level graph (default: false). * [graph] true to always output a top-level graph (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return mixed the compacted JSON-LD output. * @return mixed the compacted JSON-LD output.
*/ */
@ -60,7 +60,7 @@ function jsonld_compact($input, $ctx, $options=array()) {
* @param mixed $input the JSON-LD object to expand. * @param mixed $input the JSON-LD object to expand.
* @param assoc[$options] the options to use: * @param assoc[$options] the options to use:
* [base] the base IRI to use. * [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array the expanded JSON-LD output. * @return array the expanded JSON-LD output.
*/ */
@ -80,7 +80,7 @@ function jsonld_expand($input, $options=array()) {
* [explicit] default @explicit flag (default: false). * [explicit] default @explicit flag (default: false).
* [omitDefault] default @omitDefault flag (default: false). * [omitDefault] default @omitDefault flag (default: false).
* [optimize] optimize when compacting (default: false). * [optimize] optimize when compacting (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return stdClass the framed JSON-LD output. * @return stdClass the framed JSON-LD output.
*/ */
@ -97,7 +97,7 @@ function jsonld_frame($input, $frame, $options=array()) {
* [base] the base IRI to use. * [base] the base IRI to use.
* [format] the format if output is a string: * [format] the format if output is a string:
* 'application/nquads' for N-Quads (default). * 'application/nquads' for N-Quads (default).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array the normalized output. * @return array the normalized output.
*/ */
@ -132,7 +132,7 @@ function jsonld_from_rdf($input, $options=array()) {
* [base] the base IRI to use. * [base] the base IRI to use.
* [format] the format to use to output a string: * [format] the format to use to output a string:
* 'application/nquads' for N-Quads (default). * 'application/nquads' for N-Quads (default).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array all RDF statements in the JSON-LD object. * @return array all RDF statements in the JSON-LD object.
*/ */
@ -141,6 +141,47 @@ function jsonld_to_rdf($input, $options=array()) {
return $p->toRDF($input, $options); return $p->toRDF($input, $options);
} }
/** The default JSON-LD URL resolver. */
$jsonld_default_url_resolver = null;
/**
* Sets the default JSON-LD URL resolver.
*
* @param callable resolver(url) the URL resolver to use.
*/
function jsonld_set_url_resolver($resolver) {
global $jsonld_default_url_resolver;
$jsonld_default_url_resolver = $resolver;
}
/**
* Retrieves JSON-LD at the given URL.
*
* @param string $url the URL to to resolve.
*
* @return the JSON-LD.
*/
function jsonld_resolve_url($url) {
global $jsonld_default_url_resolver;
if($jsonld_default_url_resolver !== null) {
return call_user_func($jsonld_default_url_resolver, $url);
}
// default JSON-LD GET implementation
$opts = array('http' =>
array(
'method' => "GET",
'header' =>
"Accept: application/ld+json\r\n" .
"User-Agent: PaySwarm PHP Client/1.0\r\n"));
$stream = stream_context_create($opts);
$result = @file_get_contents($url, false, $stream);
if($result === false) {
throw new Exception("Could not GET url: '$url'");
}
return $result;
}
/** /**
* A JSON-LD processor. * A JSON-LD processor.
*/ */
@ -156,6 +197,9 @@ class JsonLdProcessor {
const RDF_NIL = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil'; const RDF_NIL = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil';
const RDF_TYPE = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type'; const RDF_TYPE = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
/** Restraints */
const MAX_CONTEXT_URLS = 10;
/** /**
* Constructs a JSON-LD processor. * Constructs a JSON-LD processor.
*/ */
@ -183,7 +227,6 @@ class JsonLdProcessor {
isset($options['optimize']) or $options['optimize'] = false; isset($options['optimize']) or $options['optimize'] = false;
isset($options['graph']) or $options['graph'] = false; isset($options['graph']) or $options['graph'] = false;
isset($options['activeCtx']) or $options['activeCtx'] = false; isset($options['activeCtx']) or $options['activeCtx'] = false;
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// expand input // expand input
@ -283,19 +326,25 @@ class JsonLdProcessor {
* @param mixed $input the JSON-LD object to expand. * @param mixed $input the JSON-LD object to expand.
* @param assoc $options the options to use: * @param assoc $options the options to use:
* [base] the base IRI to use. * [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array the expanded JSON-LD output. * @return array the expanded JSON-LD output.
*/ */
public function expand($input, $options) { public function expand($input, $options) {
// set default options // set default options
isset($options['base']) or $options['base'] = ''; isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// resolve all @context URLs in the input // resolve all @context URLs in the input
$input = self::copy($input); $input = self::copy($input);
$this->_resolveUrls($input, $options['resolver']); try {
$this->_resolveContextUrls($input, new stdClass(), $options['resolver']);
}
catch(Exception $e) {
throw new JsonLdException(
'Could not perform JSON-LD expansion.',
'jsonld.ExpandError', null, $e);
}
// do expansion // do expansion
$ctx = $this->_getInitialContext(); $ctx = $this->_getInitialContext();
@ -321,7 +370,7 @@ class JsonLdProcessor {
* [explicit] default @explicit flag (default: false). * [explicit] default @explicit flag (default: false).
* [omitDefault] default @omitDefault flag (default: false). * [omitDefault] default @omitDefault flag (default: false).
* [optimize] optimize when compacting (default: false). * [optimize] optimize when compacting (default: false).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return stdClass the framed JSON-LD output. * @return stdClass the framed JSON-LD output.
*/ */
@ -332,7 +381,6 @@ class JsonLdProcessor {
isset($options['explicit']) or $options['explicit'] = false; isset($options['explicit']) or $options['explicit'] = false;
isset($options['omitDefault']) or $options['omitDefault'] = false; isset($options['omitDefault']) or $options['omitDefault'] = false;
isset($options['optimize']) or $options['optimize'] = false; isset($options['optimize']) or $options['optimize'] = false;
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// preserve frame context // preserve frame context
@ -343,20 +391,20 @@ class JsonLdProcessor {
// expand input // expand input
$_input = $this->expand($input, $options); $_input = $this->expand($input, $options);
} }
catch(JsonLdException $e) { catch(Exception $e) {
throw new JsonLdException( throw new JsonLdException(
'Could not expand input before framing.', 'Could not expand input before framing.',
'jsonld.FrameError', $e); 'jsonld.FrameError', null, $e);
} }
try { try {
// expand frame // expand frame
$_frame = $this->expand($frame, $options); $_frame = $this->expand($frame, $options);
} }
catch(JsonLdException $e) { catch(Exception $e) {
throw new JsonLdException( throw new JsonLdException(
'Could not expand frame before framing.', 'Could not expand frame before framing.',
'jsonld.FrameError', $e); 'jsonld.FrameError', null, $e);
} }
// do framing // do framing
@ -368,10 +416,10 @@ class JsonLdProcessor {
$options['activeCtx'] = true; $options['activeCtx'] = true;
$result = $this->compact($framed, $ctx, $options); $result = $this->compact($framed, $ctx, $options);
} }
catch(JsonLdException $e) { catch(Exception $e) {
throw new JsonLdException( throw new JsonLdException(
'Could not compact framed output.', 'Could not compact framed output.',
'jsonld.FrameError', $e); 'jsonld.FrameError', null, $e);
} }
$compacted = $result['compacted']; $compacted = $result['compacted'];
@ -390,24 +438,23 @@ class JsonLdProcessor {
* @param mixed $input the JSON-LD object to normalize. * @param mixed $input the JSON-LD object to normalize.
* @param assoc $options the options to use: * @param assoc $options the options to use:
* [base] the base IRI to use. * [base] the base IRI to use.
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array the JSON-LD normalized output. * @return array the JSON-LD normalized output.
*/ */
public function normalize($input, $options) { public function normalize($input, $options) {
// set default options // set default options
isset($options['base']) or $options['base'] = ''; isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
try { try {
// expand input then do normalization // expand input then do normalization
$expanded = $this->expand($input, $options); $expanded = $this->expand($input, $options);
} }
catch(JsonLdException $e) { catch(Exception $e) {
throw new JsonLdException( throw new JsonLdException(
'Could not expand input before normalization.', 'Could not expand input before normalization.',
'jsonld.NormalizeError', $e); 'jsonld.NormalizeError', null, $e);
} }
// do normalization // do normalization
@ -456,14 +503,13 @@ class JsonLdProcessor {
* [base] the base IRI to use. * [base] the base IRI to use.
* [format] the format to use to output a string: * [format] the format to use to output a string:
* 'application/nquads' for N-Quads (default). * 'application/nquads' for N-Quads (default).
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return array all RDF statements in the JSON-LD object. * @return array all RDF statements in the JSON-LD object.
*/ */
public function toRDF($input, $options) { public function toRDF($input, $options) {
// set default options // set default options
isset($options['base']) or $options['base'] = ''; isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
try { try {
@ -510,7 +556,7 @@ class JsonLdProcessor {
* @param stdClass $active_ctx the current active context. * @param stdClass $active_ctx the current active context.
* @param mixed $local_ctx the local context to process. * @param mixed $local_ctx the local context to process.
* @param assoc $options the options to use: * @param assoc $options the options to use:
* [resolver(url, callback(err, jsonCtx))] the URL resolver to use. * [resolver(url)] the URL resolver to use.
* *
* @return stdClass the new active context. * @return stdClass the new active context.
*/ */
@ -522,15 +568,21 @@ class JsonLdProcessor {
// set default options // set default options
isset($options['base']) or $options['base'] = ''; isset($options['base']) or $options['base'] = '';
// FIXME: implement jsonld_resolve_url
isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url'; isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
// resolve URLs in local_ctx // resolve URLs in local_ctx
$local_ctx = self::copy($local_ctx); $ctx = self::copy($local_ctx);
if(is_object($local_ctx) && !property_exists($local_ctx, '@context')) { if(is_object($ctx) && !property_exists($ctx, '@context')) {
$local_ctx = (object)array('@context' => $local_ctx); $ctx = (object)array('@context' => $ctx);
}
try {
$this->_resolveContextUrls($ctx, new stdClass(), $options['resolver']);
}
catch(Exception $e) {
throw new JsonLdException(
'Could not process JSON-LD context.',
'jsonld.ContextError', null, $e);
} }
$ctx = $this->_resolveUrls($local_ctx, $options['resolver']);
// process context // process context
return $this->_processContext($active_ctx, $ctx, $options); return $this->_processContext($active_ctx, $ctx, $options);
@ -3085,75 +3137,115 @@ class JsonLdProcessor {
} }
/** /**
* Resolves external @context URLs using the given URL resolver. Each instance * Finds all @context URLs in the given JSON-LD input.
* 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 mixed $input the JSON-LD input.
* @param callable $resolver(url, callback(err, jsonCtx)) the URL resolver. * @param stdClass $urls a map of URLs (url => false/@contexts).
* * @param bool $replace true to replace the URLs in the given input with
* @return mixed the result. * the @contexts from the urls map, false not to.
*/ */
protected function _resolveUrls($input, $resolver) { protected function _findContextUrls($input, $urls, $replace) {
// keeps track of resolved URLs (prevents duplicate work) $count = count((array)$urls);
$urls = new stdClass(); if(is_array($input)) {
foreach($input as $e) {
// finds URLs in @context properties and replaces them with their $this->_findContextUrls($e, $urls, $replace);
// 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 => $v) { else if(is_object($input)) {
if($k !== '@context') { foreach($input as $k => &$v) {
$input->{$k} = $findUrls($v, $replace); if($k !== '@context') {
continue; $this->_findContextUrls($v, $urls, $replace);
} continue;
}
// array @context // array @context
if(is_array($v)) { if(is_array($v)) {
foreach($v as $i => $url) { $length = count($v);
if(is_string($url)) { for($i = 0; $i < $length; ++$i) {
// replace w/resolved @context if requested if(is_string($v[$i])) {
if($replace) { $url = $v[$i];
$v[$i] = $urls->{$url}; // replace w/@context if requested
if($replace) {
$ctx = $urls->{$url};
if(is_array($ctx)) {
// add flattened context
array_splice($v, $i, 1, $ctx);
$i += count($ctx);
$length += count($ctx);
} }
// unresolved @context found else {
else if(!property_exists($urls, $url)) { $v[$i] = $ctx;
$urls->{$url} = new stdClass();
} }
} }
// @context URL found
else if(!property_exists($urls, $url)) {
$urls->{$url} = false;
}
} }
} }
// string @context }
else if(is_string($v)) { // string @context
// replace w/resolved @context if requested else if(is_string($v)) {
if($replace) { // replace w/@context if requested
$input->{$key} = $urls->{$v}; if($replace) {
} $input->{$k} = $urls->{$v};
// unresolved @context found }
else if(!property_exists($urls, $v)) { // @context URL found
$urls->{$v} = new stdClass(); else if(!property_exists($urls, $v)) {
} $urls->{$v} = false;
} }
} }
} }
return $input; }
}; }
$input = $findUrls($input, false);
// resolve all URLs /**
foreach($urls as $url => $v) { * Resolves external @context URLs using the given URL resolver. Each
// validate URL * instance of @context in the input that refers to a URL will be replaced
if(filter_var($url, FILTER_VALIDATE_URL) === false) { * with the JSON @context found at that URL.
throw new JsonLdException( *
'Malformed URL.', 'jsonld.InvalidUrl', array('url' => $url)); * @param mixed $input the JSON-LD input with possible contexts.
* @param stdClass $cycles an object for tracking context cycles.
* @param callable $resolver(url) the URL resolver.
*
* @return mixed the result.
*/
protected function _resolveContextUrls(&$input, $cycles, $resolver) {
if(count((array)$cycles) > self::MAX_CONTEXT_URLS) {
throw new JsonLdException(
'Maximum number of @context URLs exceeded.',
'jsonld.ContextUrlError', array('max' => self::MAX_CONTEXT_URLS));
}
// for tracking the URLs to resolve
$urls = new stdClass();
// find all URLs in the given input
$this->_findContextUrls($input, $urls, false);
// queue all unresolved URLs
$queue = array();
foreach($urls as $url => $ctx) {
if($ctx === false) {
// validate URL
if(filter_var($url, FILTER_VALIDATE_URL) === false) {
throw new JsonLdException(
'Malformed URL.', 'jsonld.InvalidUrl', array('url' => $url));
}
$queue[] = $url;
} }
}
// resolve URLs in queue
foreach($queue as $url) {
// check for context URL cycle
if(property_exists($cycles, $url)) {
throw new JsonLdException(
'Cyclical @context URLs detected.',
'jsonld.ContextUrlError', array('url' => $url));
}
$_cycles = self::copy($cycles);
$_cycles->{$url} = true;
// resolve URL // resolve URL
$ctx = $resolver($url); $ctx = $resolver($url);
@ -3162,27 +3254,27 @@ class JsonLdProcessor {
if(is_string($ctx)) { if(is_string($ctx)) {
$ctx = json_decode($ctx); $ctx = json_decode($ctx);
switch(json_last_error()) { switch(json_last_error()) {
case JSON_ERROR_NONE: case JSON_ERROR_NONE:
break; break;
case JSON_ERROR_DEPTH: case JSON_ERROR_DEPTH:
throw new JsonLdException( throw new JsonLdException(
'Could not parse JSON from URL; the maximum stack depth has ' . 'Could not parse JSON from URL; the maximum stack depth has ' .
'been exceeded.', 'jsonld.ParseError', array('url' => $url)); 'been exceeded.', 'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_STATE_MISMATCH: case JSON_ERROR_STATE_MISMATCH:
throw new JsonLdException( throw new JsonLdException(
'Could not parse JSON from URL; invalid or malformed JSON.', 'Could not parse JSON from URL; invalid or malformed JSON.',
'jsonld.ParseError', array('url' => $url)); 'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_CTRL_CHAR: case JSON_ERROR_CTRL_CHAR:
case JSON_ERROR_SYNTAX: case JSON_ERROR_SYNTAX:
throw new JsonLdException( throw new JsonLdException(
'Could not parse JSON from URL; syntax error, malformed JSON.', 'Could not parse JSON from URL; syntax error, malformed JSON.',
'jsonld.ParseError', array('url' => $url)); 'jsonld.ParseError', array('url' => $url));
case JSON_ERROR_UTF8: case JSON_ERROR_UTF8:
throw new JsonLdException( throw new JsonLdException(
'Could not parse JSON from URL; malformed UTF-8 characters.', 'Could not parse JSON from URL; malformed UTF-8 characters.',
'jsonld.ParseError', array('url' => $url)); 'jsonld.ParseError', array('url' => $url));
default: default:
throw new JsonLdException( throw new JsonLdException(
'Could not parse JSON from URL; unknown error.', 'Could not parse JSON from URL; unknown error.',
'jsonld.ParseError', array('url' => $url)); 'jsonld.ParseError', array('url' => $url));
} }
@ -3195,15 +3287,18 @@ class JsonLdProcessor {
'jsonld.InvalidUrl', array('url' => $url)); 'jsonld.InvalidUrl', array('url' => $url));
} }
// FIXME: needs to recurse to resolve URLs in the result, and // use empty context if no @context key is present
// detect cycles, and limit recursion if(!property_exists($ctx, '@context')) {
if(property_exists($ctx, '@context')) { $ctx = (object)array('@context' => new stdClass());
$urls->{$url} = $ctx->{'@context'};
} }
// recurse
$this->_resolveContextUrls($ctx, $_cycles, $resolver);
$urls->{$url} = $ctx->{'@context'};
} }
// do url replacement // replace all URLS in the input
return $findUrls($input, true); $this->_findContextUrls($input, $urls, true);
} }
/** /**
@ -3634,10 +3729,10 @@ class JsonLdException extends Exception {
public function __toString() { public function __toString() {
$rval = __CLASS__ . ": [{$this->type}]: {$this->message}\n"; $rval = __CLASS__ . ": [{$this->type}]: {$this->message}\n";
if($this->details) { if($this->details) {
$rval .= 'details: ' . print_r($this->details, true) . "\n"; $rval .= 'Details: ' . print_r($this->details, true) . "\n";
} }
if($this->cause) { if($this->cause) {
$rval .= 'cause: ' . $this->cause; $rval .= 'Cause: ' . $this->cause;
} }
$rval .= $this->getTraceAsString() . "\n"; $rval .= $this->getTraceAsString() . "\n";
return $rval; return $rval;