shex.js

shex.js javascript implementation of Shape Expressions (try online)

install

npm install --save shex

test

There are two ways to run tests. You can run the default tests for whichever branch you have checked out (including main):

npm checkout shex-next
npm test

or you can clone shexSpec/shexTest next to your shex.js clone:

(cd .. && git clone https://github.com/shexSpec/shexTest --branch extends)
npm test

The test harness first looks for a sibling shexTest repo and if it doesn't find it, uses node_modules/shexTest.

test runs mocha -R dot (the dot reporter because there are around three thousand tests).

There are slower tests (command line interface, HTTP, etc) which you can run with the SLOW=<timeout in milliseconds> environment variable set. For the HTTP tests you will have to specifiy a git repository in $BRANCH, e.g. SLOW=10000 BRANCH=main TEST-cli=true'npm test

branch-specific tests

The shex.js repo includes several branches for features that are in-flight in the ShEx Community Group. NPM @shexjs/* packages are published from the shex-next repo. Each of these repos depends on some branch of the test suite. The package.json file for each branch SHOULD have that corresponding shexTest branch à la:

  "shex-test": "shexSpec/shexTest#extends"

If you are running tests from the automatically checked out shexTest module, you'll have to npm install every time you change branches. If you are running from a sibling clone of shexTest, you'll have to cd to that sibling and checkout the branch which corresponds to the shex.js branch you have checked out.

There is a post-commit hook which will probably whine at you if they are misaligned, though it will simply fail to test some features if e.g. shexTest is on main while shex.js is on extends.

validation

You can validate RDF data using the bin/validate executable or the lib/ShExValidation library described below.

validation executable

Validate something in HTTP-land:

./node_modules/shex/bin/validate \
    -x http://shex.io/examples/Issue.shex \
    -d http://shex.io/examples/Issue1.ttl \
    -s http://shex.io/examples/IssueShape \
    -n http://shex.io/examples/Issue1

That validates node http://shex.io/examples/Issue in http://shex.io/examples/Issue1.ttl against shape http://shex.io/examples/IssueShape in http://shex.io/examples/Issue.shex. The result is a JSON structure which tells you exactly how the data matched the schema.

{
  "type": "test",
  "node": "http://shex.io/examples/Issue1",
  "shape": "http://shex.io/examples/IssueShape",
  "solution": {
...
  }
}

Had we gotten a null, we'd know that the document was invalid with respect to the schema. See the ShExJ primer for a description of ShEx validation and the ShExJ specification for more details about the results format.

relative resolution

validate's -n and -s arguemtns are evaluated as IRIs relative to the (first) data and schema sources respectively. The above invocation validates the node <Issue1> in http://shex.io/examples/Issue1.ttl. This and the shape can be written as relative IRIs:

./node_modules/shex/bin/validate \
    -x http://shex.io/examples/Issue.shex \
    -d http://shex.io/examples/Issue1.ttl \
    -s IssueShape \
    -n Issue1

validation library

Parsing from the old interwebs involves a painful mix of asynchronous callbacks for getting the schema and the data and parsing the data (shorter path below): <a id="long-script"/>

var shexc = "http://shex.io/examples/Issue.shex";
var shape = "http://shex.io/examples/IssueShape";
var data = "http://shex.io/examples/Issue1.ttl";
var node = "http://shex.io/examples/Issue1";

var http = require("http");
var shex = require("shex");
var n3 = require('n3');

// generic async GET function.
function GET (url, then) {
  http.request(url, function (resp) {
    var body = "";
    resp.on('data', function (chunk) { body += chunk; });
    resp.on("end", function () { then(body); });
  }).end();
}

var Schema = null; // will be loaded and compiled asynchronously
var Triples = null; // will be loaded and parsed asynchronously
function validateWhenEverythingsLoaded () {
  if (Schema !== null && Triples !== null) {
    console.log(new shex.Validator(Schema).validate(Triples, node, shape));
  }
}

// loaded the schema
GET(shexc, function (b) {
  // callback parses the schema and tries to validate.
  Schema = shex.Parser(shexc).parse(b)
  validateWhenEverythingsLoaded();
});

// load the data
GET(data, function (b) {
  // callback parses the triples and tries to validate.
  var db = n3.Store();
  n3.Parser({baseIRI: data, format: "text/turtle"}).parse(b, function (error, triple, prefixes) {
    if (error) {
      throw Error("error parsing " + data + ": " + error);
    } else if (triple) {
      db.addQuad(triple)
    } else {
      Triples = db;
      validateWhenEverythingsLoaded();
    }
  });
});

See? That's all there was too it!

OK, that's miserable. Let's use the ShExLoader to wrap all that callback misery: <a name="loader-script"/>

const shexc = "http://shex.io/examples/IssueSchema";  // schema location
const data = "http://shex.io/examples/Issue1";        // data location
const node = "http://shex.io/examples/Issue1#Issue1"; // node in that data

const N3 = require("n3");
const ShExLoader = require("@shexjs/loader")({        // initialize with:
  fetch: require('node-fetch'),                       //   fetch implementation
  rdfjs: N3,                                          //   RdfJs Turtle parser
});
const { ctor: RdfJsDb } = require('@shexjs/neighborhood-rdfjs');
const {ShExValidator} = require("@shexjs/validator");

ShExLoader.load({shexc: [shexc]}, {turtle: [data]})
  .then(function (loaded) {
    var db = RdfJsDb(loaded.data);
    var validator = new ShExValidator(loaded.schema, db, { results: "api" });
    const smap = [                                // array of node/shape pairs
      {node: node,                                //   JSON-LD @id for node
       shape: ShExValidator.Start}                //   schemas's start shape
    ]
    var result = validator.validateShapeMap(smap);  // success if no "errors"
    console.log(JSON.stringify(result, null, 2));
  } );

Note that the shex loader takes an array of ShExC schemas, either file paths or URLs, and an array of JSON schemas (empty in this invocation) and an array of Turtle files.

conversion

As with validation (above), you can convert by either executable or library.

conversion executable

ShEx can be represented in the compact syntax

PREFIX ex: <http://ex.example/#>
<IssueShape> {                       # An <IssueShape> has:
    ex:state (ex:unassigned            # state which is
              ex:assigned),            #   unassigned or assigned.
    ex:reportedBy @<UserShape>        # reported by a <UserShape>.
}

or in JSON:

{ "type": "schema", "start": "http://shex.io/examples/IssueShape",
  "shapes": {
    "http://shex.io/examples/IssueShape": { "type": "shape",
      "expression": { "type": "eachOf",
        "expressions": [
          { "type": "tripleConstraint", "predicate": "http://ex.example/#state",
            "valueExpr": { "type": "valueClass", "values": [
                "http://ex.example/#unassigned", "http://ex.example/#assigned"
          ] } },
          { "type": "tripleConstraint", "predicate": "http://ex.example/#reportedBy",
            "valueExpr": { "type": "valueClass", "reference": "http://shex.io/examples/UserShape" }
          }
] } } } }

You can convert between them with shex-to-json:

./node_modules/shex/bin/shex-to-json http://shex.io/examples/Issue.shex

and, less elegantly, back with json-to-shex.

conversion by library

As with validation, the ShExLoader wrapes callbacks and simplifies parsing the libraries:

var shexc = "http://shex.io/examples/Issue.shex";

var shex = require("shex");
shex.Loader.load({shexc: [shexc]}, null).then(function (loaded) {
    console.log(JSON.stringify(loaded.schema, null, "  "));
});

There's no actual conversion; the JSON representation is just the stringification of the parsed schema.

local files

Command line arguments which don't start with http:// or https:// are assumed to be file paths. We can create a local JSON version of the Issues schema:

./node_modules/shex/bin/shex-to-json http://shex.io/examples/Issue.shex > Issue.json

and use it to validate the Issue1.ttl as we did above:

./node_modules/shex/bin/validate \
    -j Issue.json \
    -d http://shex.io/examples/Issue1.ttl \
    -s http://shex.io/examples/IssueShape \
    -n http://shex.io/examples/Issue1

Of course the data file can be local as well.

Happy validating!

materialize

Materialize is used to transform from a source schema to a target schema after validation is done.

The syntax is:

materialize `-t <target schema>`|-h [-j `<JSON Vars File>`] [-r `<RDF root IRI>`]

Materialize reads the output from the validate tool from STDIN an