128 lines
4.7 KiB
Markdown
128 lines
4.7 KiB
Markdown
Introduction
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------------
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JSON, as specified in RFC4627, is a simple language for representing
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objects on the Web. Linked Data is a way of describing content across
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different documents or Web sites. Web resources are described using
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IRIs, and typically are dereferencable entities that may be used to find
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more information, creating a "Web of Knowledge". JSON-LD is intended to
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be a simple publishing method for expressing not only Linked Data in
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JSON, but for adding semantics to existing JSON.
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This library is an implementation of the [JSON-LD] specification
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in [PHP].
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JSON-LD is designed as a light-weight syntax that can be used to express
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Linked Data. It is primarily intended to be a way to express Linked Data
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in Javascript and other Web-based programming environments. It is also
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useful when building interoperable Web Services and when storing Linked
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Data in JSON-based document storage engines. It is practical and
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designed to be as simple as possible, utilizing the large number of JSON
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parsers and existing code that is in use today. It is designed to be
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able to express key-value pairs, RDF data, RDFa [RDFA-CORE] data,
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Microformats [MICROFORMATS] data, and Microdata [MICRODATA]. That is, it
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supports every major Web-based structured data model in use today.
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The syntax does not require many applications to change their JSON, but
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easily add meaning by adding context in a way that is either in-band or
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out-of-band. The syntax is designed to not disturb already deployed
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systems running on JSON, but provide a smooth migration path from JSON
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to JSON with added semantics. Finally, the format is intended to be fast
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to parse, fast to generate, stream-based and document-based processing
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compatible, and require a very small memory footprint in order to operate.
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## Quick Examples
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```php
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$doc = (object)array(
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"http://schema.org/name" => "Manu Sporny",
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"http://schema.org/url" => (object)array("@id" => "http://manu.sporny.org/"),
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"http://schema.org/image" => (object)array("@id" => "http://manu.sporny.org/images/manu.png")
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);
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$context = (object)array(
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"name" => "http://schema.org/name",
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"homepage" => (object)array("@id" => "http://schema.org/url", "@type" => "@id"),
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"image" => (object)array("@id" => "http://schema.org/image", "@type" => "@id")
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);
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// compact a document according to a particular context
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// see: http://json-ld.org/spec/latest/json-ld/#compacted-document-form
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$compacted = jsonld_compact($doc, $context);
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echo json_encode($compacted, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
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/* Output:
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{
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"@context": {...},
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"image": "http://manu.sporny.org/images/manu.png",
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"homepage": "http://manu.sporny.org/",
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"name": "Manu Sporny"
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}
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*/
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// compact using URLs
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jsonld_compact('http://example.org/doc', 'http://example.org/context');
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// expand a document, removing its context
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// see: http://json-ld.org/spec/latest/json-ld/#expanded-document-form
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$expanded = jsonld_expand($compacted) {
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echo json_encode($expanded, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
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/* Output:
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{
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"http://schema.org/image": [{"@id": "http://manu.sporny.org/images/manu.png"}],
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"http://schema.org/name": [{"@value": "Manu Sporny"}],
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"http://schema.org/url": [{"@id": "http://manu.sporny.org/"}]
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}
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*/
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// expand using URLs
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jsonld_expand('http://example.org/doc');
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// flatten a document
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// see: http://json-ld.org/spec/latest/json-ld/#flattened-document-form
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$flattened = jsonld_flatten($doc);
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// all deep-level trees flattened to the top-level
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// frame a document
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// see: http://json-ld.org/spec/latest/json-ld-framing/#introduction
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$framed = jsonld_frame($doc, $frame);
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// document transformed into a particular tree structure per the given frame
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// normalize a document
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$normalized = jsonld_normalize($doc, array('format' => 'application/nquads'));
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// normalized is a string that is a canonical representation of the document
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// that can be used for hashing
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```
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Commercial Support
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------------------
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Commercial support for this library is available upon request from
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Digital Bazaar: support@digitalbazaar.com
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Source
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------
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The source code for the PHP implementation of the JSON-LD API
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is available at:
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http://github.com/digitalbazaar/php-json-ld
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This library includes a sample testing utility which may be used to verify
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that changes to the processor maintain the correct output.
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To run the sample tests you will need to get the test suite files by cloning
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the [json-ld.org repository][json-ld.org] hosted on GitHub.
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https://github.com/json-ld/json-ld.org
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Then run the PHPUnit test.php application and point it at the directory
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containing the tests.
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phpunit test.php -d {PATH_TO_JSON_LD_ORG/test-suite}
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[PHP]: http://php.net
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[JSON-LD]: http://json-ld.org/
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[json-ld.org]: https://github.com/json-ld/json-ld.org
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