json-ld.net

Introduction

This library is an implementation of the JSON-LD specification in C#.

JSON, as specified in RFC7159, is a simple language for representing objects on the Web. Linked Data is a way of describing content across different documents or Web sites. Web resources are described using IRIs, and typically are dereferencable entities that may be used to find more information, creating a "Web of Knowledge". JSON-LD is intended to be a simple publishing method for expressing not only Linked Data in JSON, but for adding semantics to existing JSON.

JSON-LD is designed as a light-weight syntax that can be used to express Linked Data. It is primarily intended to be a way to express Linked Data in JavaScript and other Web-based programming environments. It is also useful when building interoperable Web Services and when storing Linked Data in JSON-based document storage engines. It is practical and designed to be as simple as possible, utilizing the large number of JSON parsers and existing code that is in use today. It is designed to be able to express key-value pairs, RDF data, RDFa data, Microformats data, and Microdata. That is, it supports every major Web-based structured data model in use today.

The syntax does not require many applications to change their JSON, but easily add meaning by adding context in a way that is either in-band or out-of-band. The syntax is designed to not disturb already deployed systems running on JSON, but provide a smooth migration path from plain JSON to semantically enhanced JSON. Finally, the format is intended to be fast to parse, fast to generate, stream-based and document-based processing compatible, and require a very small memory footprint in order to operate.

You can read more about JSON-LD on the JSON-LD website.

Conformance

This library aims to conform with the following:

• JSON-LD 1.0, W3C Recommendation, 2014-01-16, and any errata
• JSON-LD 1.0 Processing Algorithms and API, W3C Recommendation, 2014-01-16, and any errata
• JSON-LD 1.0 Framing, Unofficial Draft, 2012-08-30
• Working Group test suite

The [JSON-LD Working Group][json-ld-wg] is now developing JSON-LD 1.1. Library updates to conform with newer specifications will happen as features stabilize and development time and resources permit.

• JSON-LD 1.1, W3C Working Draft, 2018-12-14 or newer
• JSON-LD 1.1 Processing Algorithms and API, W3C Working Draft, 2018-12-14 or newer
• JSON-LD 1.1 Framing, W3C Working Draft, 2018-12-14 or newer

The test runner is often updated to note or skip newer tests that are not yet supported.

Supported frameworks

• .NET 4.0
• .NET Standard 1.3 and 2.0
• Portable .NET 4.5, Windows 8

Installation

dotnet CLI

dotnet new console
dotnet add package json-ld.net

using JsonLD.Core;
using Newtonsoft.Json.Linq;
using System;

namespace JsonLD.Demo
{
    internal class Program
    {
        private static void Main()
        {
            var json = "{'@context':{'test':'http://www.test.com/'},'test:hello':'world'}";
            var document = JObject.Parse(json);
            var expanded = JsonLdProcessor.Expand(document);
            Console.WriteLine(expanded);
        }
    }
}

Examples

Example data and context used throughout examples below:

doc.json

{
    "@id": "http://example.org/ld-experts",
    "http://schema.org/name": "LD Experts",
    "http://schema.org/member": [{
        "@type": "http://schema.org/Person",
        "http://schema.org/name": "Manu Sporny",
        "http://schema.org/url": {"@id": "http://manu.sporny.org/"},
        "http://schema.org/image": {"@id": "http://manu.sporny.org/images/manu.png"}
    }]
}

context.json

{
    "name": "http://schema.org/name",
    "member": "http://schema.org/member",
    "homepage": {"@id": "http://schema.org/url", "@type": "@id"},
    "image": {"@id": "http://schema.org/image", "@type": "@id"},
    "Person": "http://schema.org/Person",
    "@vocab": "http://example.org/",
    "@base": "http://example.org/"
}

Compact

Compaction is the process of applying a developer-supplied context to shorten IRIs to terms or compact IRIs, and JSON-LD values expressed in expanded form to simple values such as strings or numbers. Often this makes it simpler to work with a document as the data is expressed in application-specific terms. Compacted documents are also typically easier to read for humans.

var doc = JObject.Parse(_docJson);
var context = JObject.Parse(_contextJson);
var opts = new JsonLdOptions();
var compacted = JsonLdProcessor.Compact(doc, context, opts);
Console.WriteLine(compacted);

/*

Output:
{
    "@id": "ld-experts",
    "member": {
        "@type": "Person",
        "image": "http://manu.sporny.org/images/manu.png",
        "name": "Manu Sporny",
        "homepage": "http://manu.sporny.org/"
    },
    "name": "LD Experts",
    "@context": . . .
}

*/

Expand

Exapansion is the process of taking a JSON-LD document and applying a @context such that all IRIs, types, and values are expanded so that the @context is no longer necessary.

var expanded = JsonLdProcessor.Expand(compacted);
Console.WriteLine(expanded);

/*

Output:
[
    {
        "@id": "http://test.com/ld-experts",
        "http://schema.org/member": [
            {
                "http://schema.org/url": [
                    {
                        "@id": "http://manu.sporny.org/"
                    }
                ],
                "http://schema.org/image": [
                    {
                        "@id": "http://manu.sporny.org/images/manu.png"
                    }
                ],
                "http://schema.org/name": [
                    {
                        "@value": "Manu Sporny"
                    }
                ]
            }
        ],
        "http://schema.org/name": [
            {
                "@value": "LD Experts"
            }
        ]
    }
]

*/


*/

Flatten

Flattening collects all properties of a node in a single JSON object and labels all blank nodes with blank node identifiers. This ensures a shape of the data and consequently may drastically simplify the code required to process JSON-LD in certain applications.

var doc = JObject.Parse(_docJson);
var context = JObject.Parse(_contextJson);
var opts = new JsonLdOptions();
var flattened = JsonLdProcessor.Flatten(doc, context, opts);
Console.WriteLine(flattened);

/*

Output:
{
    "@context": . . .,
    "@graph": [
        {
            "@id": "_:b0",
            "@type": "Person",
            "image": "http://manu.sporny.org/images/manu.png",
            "name": "Manu Sporny",
            "homepage": "http://manu.sporny.org/"
        },
        {
            "@id": "ld-experts",
            "member": {
                "@id": "_:b0"
            },
            "name": "LD Experts"
        }
    ]
}

*/

Frame

Framing is used to shape the data in a JSON-LD document, using an example frame document which is used to both match the flattened data and show an example of how the resulting data should be shaped. Matching is performed by using properties present in the frame to find objects in the data that share common values. Matching can be done either using all properties present in the frame, or any property in the frame. By chaining together objects using matched property values, objects can be embedded within one another.

A frame also includes a context, which is used for compacting the resulting framed output.

For the framing example below, the framing document is defined as follows:

{
    "@context": {
        "name": "http://schema.org/name",
        "member": {"@id": "http://schema.org/member", "@type": "@id"},
        "homepage": {"@id": "http://schema.org/url", "@type": "@id"},
        "image": {"@id": "http://schema.org/image", "@type": "@id"},
        "Person": "http://schema.org/Person"
    },
    "@type": "Person"
}

And we use it like this:

var doc = JObject.Parse(_docJson);
var frame = JObject.Parse(_frameJson);
var opts = new JsonLdOptions();
var flattened = JsonLdProcessor.Frame(doc, frame, opts);
Console.WriteLine(flattened);

/*

Output:
{
    "@context": . . .,
    "@graph": [
        {
            "@id": "_:b0",
            "@type": "Person",
            "image": "http://manu.sporny.org/images/manu.png",
            "name": "Manu Sporny",
            "homepage": "http://manu.sporny.org/"
        }
    ]
}

*/

Normalize

Normalization (aka. canonicalization) converts the document into a graph of objects that is a canonical representation of the document that can be used for hashing, comparison, etc.

var doc = JObject.Parse(_docJson);
var opts = new JsonLdOptions();
var normalized = (RDFDataset)JsonLdProcessor.Normalize(doc, opts);
Console.WriteLine(normalized.Dump());

/*

Output:
@default
    subject
            type      blank node
            value     _:c14n0
    predicate
            type      IRI
            value     http://schema.org/image
    object
            type      IRI
            value     http://manu.sporny.org/images/manu.png
    ---
    subject
            type      blank node
            value     _:c14n0
    predicate
            type      IRI
            value     http://schema.org/name
    object
            type      literal
            value     Manu Sporny
            datatype  http://www.w3.org/2001/XMLSchema#string
    ---
    subject
            type      blank node
            value     _:c14n0
    predicate
            type      IRI
            value     http://schema.org/url
    object
            type      IRI
            value     http://manu.sporny.org/
    ---
    subject
            type      blank node
            value     _:c14n0
    predicate
            type      IRI
            value     http://www.w3.org/1999/02/22-rdf-syntax-ns#type
    object
            type      IRI
            value     http://schema.org/Person
    ---
    subject
            type      IRI
            value     http://example.org/ld-experts
    predicate
            type      IRI
            value     http://schema.org/member
    object
            type      blank node
            value     _:c14n0
    ---
    subject
            type      IRI
            value     http://example.org/ld-experts
    predicate
            type      IRI
            value     http://schema.org/name
    object
            type      literal
            value     LD Experts
            datatype  http://www.w3.org/2001/XMLSchema#string
    ---

*/

ToRDF

JSON-LD is a concrete RDF syntax as described in RDF 1.1 Concepts and Abstract Syntax. Hence, a JSON-LD document is both an RDF document and a JSON document and correspondingly represents an instance of an RDF data model. The procedure to deserialize a JSON-LD document to an RDF dataset (and, optionally, to RDF N-Quads) involves the following steps:

1. Expand the JSON-LD document, removing any context; this ensures that properties, types, and values are given their full representation as IRIs and expanded values.
2. Flatten the document, which turns the document into an array of node objects.
3. Turn each node object into a series of RDF N-Quads.

The processor's ToRDF method carries out these steps for you, like this:

var doc = JObject.Parse(_docJson);
var opts = new JsonLdOptions();
var rdf = (RDFDataset)JsonLdProcessor.ToRDF(doc, opts);

var serialized = RDFDatasetUtils.ToNQuads(rdf); // serialize RDF to string
Console.WriteLine(serialized);

/*

Output:
<http://example.org/ld-experts> <http://schema.org/member> _:b0 .
<http://example.org/ld-experts> <http://schema.org/name> "LD Experts" .
_:b0 <http://schema.org/image> <http://manu.sporny.org/images/manu.png> .
_:b0 <http://schema.org/name> "Manu Sporny" .
_:b0 <http://schema.org/url> <http://manu.sporny.org/> .
_:b0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://schema.org/Person> .

*/

or using a custom RDF renderer object, like this:

private class JSONLDTripleCallback : IJSONLDTripleCallback
{
    public object Call(RDFDataset dataset) =>
        RDFDatasetUtils.ToNQuads(dataset); // serialize the RDF dataset as NQuads
}

internal static void Run()
{
    var doc = JObject.Parse(_docJson);
    var callback = new JSONLDTripleCallback();
    var serialized = JsonLdProcessor.ToRDF(doc, callback);
    Console.WriteLine(serialized);

    /*

    Output:
    <http://example.org/ld-experts> <http://schema.org/member> _:b0 .
    <http://example.org/ld-experts> <http://schema.org/name> "LD Experts" .
    _:b0 <http://schema.org/image> <http://manu.sporny.org/images/manu.png> .
    _:b0 <http://schema.org/name> "Manu Sporny" .
    _:b0 <http://schema.org/url> <http://manu.sporny.org/> .
    _:b0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://schema.org/Person> .

    */
}

FromRDF

Serialization from RDF N-Quads into JSON-LD can be thought of as the inverse of the last of the three steps described in summary Deserialization described in the ToRDF method documentation above. Serialization creates an expanded JSON-LD document closely matching the N-Quads from RDF, using a single node object for all N-Quads having a common subject, and a single property for those N-Quads also having a common predicate.

In practice, it looks like this:

the variable serialized is populated with RDF N-Quads values resulting from the code in the ToRDF example above

var opts = new JsonLdOptions();
var jsonld = JsonLdProcessor.FromRDF(serialized, opts);
Console.WriteLine(jsonld);

/*

Output:
[
    {
        "@id": "_:b0",
        "http://schema.org/image": [
            {
                "@id": "http://manu.sporny.org/images/manu.png"
            }
        ],
        "http://schema.org/name": [
            {
                "@value": "Manu Sporny"
            }
        ],
        "http://schema.org/url": [
            {
                "@id": "http://manu.sporny.org/"
            }
        ],
        "@type": [
            "http://schema.org/Person"
        ]
    },
    {
        "@id": "http://example.org/ld-experts",
        "http://schema.org/member": [
            {
                "@id": "_:b0"
            }
        ],
        "http://schema.org/name": [
            {
                "@value": "LD Experts"
            }
        ]
    }
]
*/

or using a custom RDF parser:

private class CustomRDFParser : IRDFParser
{
    public RDFDataset Parse(JToken input)
    {
        // by public decree, references to example.org are normalized to https going forward...
        var converted = ((string)input).Replace("http://example.org/", "https://example.org/");
        return RDFDatasetUtils.ParseNQuads(converted);
    }
}

internal static void Run()
{
    var parser = new CustomRDFParser();
    var jsonld = JsonLdProcessor.FromRDF(_serialized, parser);
    Console.WriteLine(jsonld);

    /*

    Output:
    [
        {
            "@id": "_:b0",
            "http://schema.org/image": [
                {
                    "@id": "http://manu.sporny.org/images/manu.png"
                }
            ],
            "http://schema.org/name": [
                {
                    "@value": "Manu Sporny"
                }
            ],
            "http://schema.org/url": [
                {
                    "@id": "http://manu.sporny.org/"
                }
            ],
            "@type": [
                "http://schema.org/Person"
            ]
        },
        {
            "@id": "https://example.org/ld-experts",
            "http://schema.org/member": [
                {
                    "@id": "_:b0"
                }
            ],
            "http://schema.org/name": [
                {
                    "@value": "LD Experts"
                }
            ]
        }
    ]
    */
}

Custom DocumentLoader

By replacing the default documentLoader object placed on the JsonLdProcessor, it is possible to alter the behaviour when retrieving a remote document (e.g. a context document) required to execute a given algorithm (e.g. Expansion).

public class CustomDocumentLoader : DocumentLoader
{
    private static readonly string _cachedExampleOrgContext = Res.ReadString("context.json");

    public override RemoteDocument LoadDocument(string url)
    {
        if (url == "http://example.org/context.jsonld") // we have this cached locally
        {
            var doc = new JObject(new JProperty("@context", JObject.Parse(_cachedExampleOrgContext)));
            return new RemoteDocument(url, doc);
        }
        else
        {
            return base.LoadDocument(url);
        }
    }
}

public static void Run()
{
    var doc = JObject.Parse(_docJson);
    var remoteContext = JObject.Parse("{'@context':'http://example.org/context.jsonld'}");
    var opts = new JsonLdOptions { documentLoader = new CustomDocumentLoader() };
    var compacted = JsonLdProcessor.Compact(doc, remoteContext, opts);
    Console.WriteLine(compacted);

    /*

    Output:
    {
        "@id": "http://example.org/ld-experts",
        "member": {
            "@type": "Person",
            "image": "http://manu.sporny.org/images/manu.png",
            "name": "Manu Sporny",
            "homepage": "http://manu.sporny.org/"
        },
        "name": "LD Experts"
    }

    */
}

Contributing

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.

Pull requests for json-ld.net are welcome, to get started install the latest tools for .NET Core:

• .NET Core
• .NET Core tutorial

Build and Tests

On Windows, you can execute build.ps1, which will create a nupkg and run tests for both .NET desktop and .NET Core.

On both Windows and all other supported operating systems, you can run dotnet build to build and dotnet test to run the tests.

Origin

This project began life as a Sharpen-based auto-port from jsonld-java.

Documentation for this library is in part drawn from https://github.com/linked-data-dotnet/json-ld.net