LevelGraph-JSONLD

LevelGraph-JSONLD is a plugin for LevelGraph that adds the ability to store, retrieve and delete JSON-LD objects. In fact, it is a full-blown Object-Document-Mapper (ODM) for LevelGraph.

Install

Node.js

Adding support for JSON-LD to LevelGraph is easy:

$ npm install level levelgraph levelgraph-jsonld --save

Then in your code:

var level      = require('level'),
    yourDB     = level('./yourdb'),
    levelgraph = require('levelgraph'),
    jsonld     = require('levelgraph-jsonld'),
    db         = jsonld(levelgraph(yourDB));

At the moment it requires node v0.10.x, but the port to node v0.8.x should be straighforward. If you need it, just open a pull request.

Browser

If you use browserify you can use this package in a browser just as in node.js. Please also take a look at Browserify section in LevelGraph package

You can also use standalone browserified version from ./build directory or use bower

$ bower install levelgraph-jsonld --save

It will also install its dependency levelgraph! Now you can simply:

<script src="bower_components/levelgraph/build/levelgraph.js"></script>
<script src="bower_components/levelgraph-jsonld/build/levelgraph-jsonld.js"></script>
<script>
  var db = levelgraphJSONLD(levelgraph('yourdb'));
</script>

Usage

We assume in following examples that you created database as explained above!

var level  = require('level'),
    yourDB = level('./yourdb'),
    db     = levelgraphJSONLD(levelgraph(yourDB));

'base' can also be specified when you create the db:

var level      = require('level'),
    yourDB     = level('./yourdb'),
    levelgraph = require('levelgraph'),
    jsonld     = require('levelgraph-jsonld'),
    opts       = { base: 'http://matteocollina.com/base' },
    db         = jsonld(levelgraph(yourDB), opts);

From v1, overwriting and deleting is more conservative. If you rely on the previous behavior you can set the overwrite option to true (when creating the db or as options to put and del) to:

• overwrite all existing triples when using put
• delete all blank nodes recursively when using del (cf upcoming cut function) This old api will be phased out.

Put

Please keep in mind that LevelGraph-JSONLD doesn't store the original JSON-LD document but decomposes it into triples! It stores literals double quoted with datatype if other then string. If you use plain LevelGraph methods, instead trying to match number 42 you need to try matching "42"^^http://www.w3.org/2001/XMLSchema#integer

Storing triples from JSON-LD document is extremely easy:

var manu = {
  "@context": {
    "name": "http://xmlns.com/foaf/0.1/name",
    "homepage": {
      "@id": "http://xmlns.com/foaf/0.1/homepage",
      "@type": "@id"
    }
  },
  "@id": "http://manu.sporny.org#person",
  "name": "Manu Sporny",
  "homepage": "http://manu.sporny.org/"
};

db.jsonld.put(manu, function(err, obj) {
  // do something after the obj is inserted
});

if the top level objects have no '@id' key, one will be generated for each, using a UUID and the 'base' argument, like so:

delete manu['@id'];
db.jsonld.put(manu, { base: 'http://this/is/an/iri' }, function(err, obj) {
  // obj['@id'] will be something like
  // http://this/is/an/iri/b1e783b0-eda6-11e2-9540-d7575689f4bc
});

'base' can also be specified when you create the db.

LevelGraph-JSONLD also support nested objects, like so:

var nested = {
  "@context": {
    "name": "http://xmlns.com/foaf/0.1/name",
    "knows": "http://xmlns.com/foaf/0.1/knows"
  },
  "@id": "http://matteocollina.com",
  "name": "Matteo",
  "knows": [{
    "name": "Daniele"
  }, {
    "name": "Lucio"
  }]
};

db.jsonld.put(nested, function(err, obj) {
  // do something...
});

Get

Retrieving a JSON-LD object from the store requires its '@id':

db.jsonld.get(manu['@id'], { '@context': manu['@context'] }, function(err, obj) {
  // obj will be the very same of the manu object
});

The format of the loaded object is entirely specified by the '@context', so have fun :).

As with 'put' it correctly support nested objects. If nested objects didn't originally include '@id' properties, now they will have them since 'put' generates them by using UUID and formats them as blank node identifiers:

var nested = {
  "@context": {
    "name": "http://xmlns.com/foaf/0.1/name",
    "knows": "http://xmlns.com/foaf/0.1/knows"
  },
  "@id": "http://matteocollina.com",
  "name": "Matteo",
  "knows": [{
    "name": "Daniele"
  }, {
    "name": "Lucio"
  }]
};

db.jsonld.put(nested, function(err, obj) {
  // obj will be
  // {
  //   "@context": {
  //     "name": "http://xmlns.com/foaf/0.1/name",
  //     "knows": "http://xmlns.com/foaf/0.1/knows"
  //   },
  //   "@id": "http://matteocollina.com",
  //   "name": "Matteo",
  //   "knows": [{
  //     "@id": "_:7053c150-5fea-11e3-a62e-adadc4e3df79",
  //     "name": "Daniele"
  //   }, {
  //     "@id": "_:9d2bb59d-3baf-42ff-ba5d-9f8eab34ada5",
  //     "name": "Lucio"
  //   }]
  // }
});

Delete

In order to delete an object, you need to pass the document to the 'del' method which will delete only the properties specified in the document:

db.jsonld.del(manu, function(err) {
  // do something after it is deleted!
});

Note that blank nodes are ignored, so to delete blank nodes you need to pass the cut: true option (you can also add the recurse: trueoption) or use the 'cut' method below.

Note that since v1 'del' doesn't support passing an IRI anymore.

Cut

In order to delete the blank nodes object, you can just pass it's '@id' to the 'cut' method:

db.jsonld.cut(manu['@id'], function(err) {
  // do something after it is cut!
});

You can also pass an object, but in this case the properties are not used to determine which triples will be deleted and only the @ids are considered.

Using the recurse option you can follow all links and blank nodes (which might result in deleting more data than you expect)

db.jsonld.cut(manu['@id'], { recurse: true }, function(err) {
  // do something after it is cut!
});

Searching with LevelGraph

LevelGraph-JSONLD does not support searching for objects, because that problem is already solved by LevelGraph itself. This example search finds friends living near Paris:

var manu = {
  "@context": {
    "@vocab": "http://xmlns.com/foaf/0.1/",
    "homepage": { "@type": "@id" },
    "knows": { "@type": "@id" },
    "based_near": { "@type": "@id" }
  },
  "@id": "http://manu.sporny.org#person",
  "name": "Manu Sporny",
  "homepage": "http://manu.sporny.org/",
  "knows": [{
    "@id": "https://my-profile.eu/people/deiu/card#me",
    "name": "Andrei Vlad Sambra",
    "based_near": "http://dbpedia.org/resource/Paris"
  }, {
    "@id": "http://melvincarvalho.com/#me",
    "name": "Melvin Carvalho",
    "based_near": "http://dbpedia.org/resource/Honolulu"
  }, {
    "@id": "http://bblfish.net/people/henry/card#me",
    "name": "Henry Story",
    "based_near": "http://dbpedia.org/resource/Paris"
  }, {
    "@id": "http://presbrey.mit.edu/foaf#presbrey",
    "name": "Joe Presbrey",
    "based_near": "http://dbpedia.org/resource/Cambridge"
  }]
};

var paris = 'http://dbpedia.org/resource/Paris';

db.jsonld.put(manu, function(){
  db.search([{
    subject: manu['@id'],
    predicate: 'http://xmlns.com/foaf/0.1/knows',
    object: db.v('webid')
  }, {
    subject: db.v('webid'),
    predicate: 'http://xmlns.com/foaf/0.1/based_near',
    object: paris
  }, {
    subject: db.v('webid'),
    predicate: 'http://xmlns.com/foaf/0.1/name',
    object: db.v('name')
  }
  ], function(err, solution) {
    // solution contains
    // [{
    //   webid: 'http://bblfish.net/people/henry/card#me',
    //   name: '"Henry Story"'
    // }, {
    //   webid: 'https://my-profile.eu/people/deiu/card#me',
    //   name: '"Andrei Vlad Sambra"'
    // }]
  });
});

Changes

CHANGELOG.md including migration info for breaking changes

Contributing to LevelGraph-JSONLD

• Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
• Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
• Fork the project
• Start a feature/bugfix branch
• Commit and push until you are happy with your contribution
• Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
• Please try not to mess with the Makefile and package.json. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

LICENSE - "MIT License"

Copyright (c) 2013-2017 Matteo Collina and LevelGraph-JSONLD contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.