LevelGraph-N3

LevelGraph-N3 is a plugin for LevelGraph that adds the ability to store, fetch and process N3 and turtle files.

Install

Node.js

Adding support for N3 to LevelGraph is easy:

$ npm install level levelgraph levelgraph-n3 --save

Then in your code:

var level = require('level'),
    levelgraph = require('levelgraph'),
    levelgraphN3 = require('levelgraph-n3'),
    db = levelgraphN3(levelgraph(level('yourdb')));

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

Usage

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

var db = levelgraphN3(levelgraph(level("yourdb")));

Importing n3 files

In code:

var fs = require("fs");
 
var stream = fs.createReadStream("./triples.n3")
               .pipe(db.n3.putStream());
 
stream.on("finish", function() {
  console.log("Import completed");
});

Alternatively, you can run the import CLI tool by running npm install, then:

./import.js path/to/n3/file(s)

with the following optional flags:

-o or --output followed by the desired DB path. If not specified, path will be at ./db.

-q or --quiet will silence status updates during the import process. Otherwise, progress information is displayed.

File extensions must be .n3 or .nt. Additionally, there is glob support, so for example *.nt will import all the matching n-triple files.

Get and Put

Storing an N3 file in the database is extremey easy:

var turtle = "@prefix c: <http://example.org/cartoons#>.\n" +
             "c:Tom a c:Cat.\n" +
             "c:Jerry a c:Mouse;\n" +
             "        c:smarterThan c:Tom;\n" +
             "        c:place \"fantasy\".";
 
db.n3.put(turtle, function(err) {
  // do something after the triple is inserted
});

Retrieving it through pattern-matching is extremely easy:

db.n3.get({ subject: "http://example.org/cartoons#Tom" }, function(err, turtle) {
  // turtle is "<http://example.org/cartoons#Tom> a <http://example.org/cartoons#Cat> .\n";
});

It even support a Stream interface:

var stream = db.n3.getStream({ subject: "http://example.org/cartoons#Tom" });
stream.on("data", function(data) {
  // data is "<http://example.org/cartoons#Tom> a <http://example.org/cartoons#Cat> .\n";
});
stream.on("end", done);

Exporting NTriples from LevelGraph

LevelGraph-N3 allows to export ntriples from a LevelGraph database. LevelGraph-N3 augments the a standard search method with a { n3: ... } option that specifies the subject, predicate and object of the created triples. It follows the same structure of the { materialized: ... } option (see https://github.com/levelgraph/levelgraph#searches).

Here is an example:

db.search([{
  subject: db.v("s"),
  predicate: "http://example.org/cartoons#smarterThan",
  object: db.v("o")
}], {
  n3: {
    subject: db.v("o"),
    predicate: "http://example.org/cartoons#dumberThan",
    object: db.v("s")
  }
}, function(err, turtle) {
  // turtle is "<http://example.org/cartoons#Tom> <http://example.org/cartoons#dumberThan> <http://example.org/cartoons#Jerry> .\n"
});

It also supported by the searchStream method.

Changes

CHANGELOG.md including migration info for breaking changes

Contributing to LevelGraph-N3

• 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) 2013-2015 Matteo Collina (http://matteocollina.com)

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.