xAPI Validator

A stand-alone Javascript validator for Experience API (xAPI) statements.

The xAPI Validator is configured to work in the browser or on Node. Both AMD and global-variable usage are supported.

No external libraries or schema files are necessary.

Presently only the 1.0.0 version of the xAPI specification is targeted for validation.

Usage

The core functionality is exposed via xapiValidator.validateStatement(statement)

Input

The input statement may either be JSON string of an xAPI statement or a Javascript object that aligns with the deserialization of a JSON xAPI statement.

Using an object

var report = xapiValidator.validateStatement({
                "id": "fd41c918-b88b-4b20-a0a5-a4c32391aaa0",
                "actor": {
                    "mbox": "mailto:bob@example.com"
                },
                "verb": { 
                    "id": "http://adlnet.gov/expapi/verbs/created",
                    "display" :{"en-US": "created"}
                },
                "object": {
                    "id": "http://example.com/activities/someUniqueId",
                    "objectType": "Activity"
                }
            });

Direct JSON

var report = xapiValidator.validateStatement("{\"id\":\"fd41c918-b88b-4b20-a0a5-a4c32391aaa0\",\"actor\":{\"mbox\":\"mailto:bob@example.com\"},\"verb\":{\"id\":\"http:\/\/adlnet.gov\/expapi\/verbs\/created\",\"display\":{\"en-US\":\"created\"}},\"object\":{\"id\":\"http:\/\/example.com\/activities\/someUniqueId\",\"objectType\":\"Activity\"}}");

Output

The produced report object contains three key properties: a collection of any errors found, the version of xAPI validated against, and reference to the statement object instance that was evaluated (after JSON parsing, if necessary).

var report = {
                version: "1.0.0",
                errors: [
                    {
                        trace : "statement.id",
                        message : "Id was not a valid UUID",
                        level : "MUST_VIOLATION"
                    },
                    {
                        trace : "statement.object.objectType",
                        message : "objectType property was required to be a string but was absent.",
                        level : "SHOULD_VIOLATION"
                    }
                ],
                instance : {
                    "id": "abc123",
                    "actor": {
                        "mbox": "mailto:charles@example.com"
                    },
                    "verb": { 
                        "id": "http://adlnet.gov/expapi/verbs/created",
                        "display" :{"en-US": "created"}
                    },
                    "object": {
                        "id": "http://example.com/activities/someUniqueId",
                    }
                }
};

Validation Error objects

Each object in the errors Array provides a trace property, to help track down the precise location of the error in the supplied schema.

{
    trace: "statement.context.contextActivities.group[2].id",
    message: "id property, if present, must be a URI string.",
    level: "MUST_VIOLATION"
}

The trace is formatted akin to Javascript object and Array access notation. It should be possible to copy a trace into a Javascript console or debugger watch field, substitute the initial "statement" with the actual name of the evaluated statement variable, and thus directly see the erroneous value.

The message property gives a human-readable explanation of the error.

The level property clarifies whether a MUST, SHOULD, or MAY requirement from the xAPI specification has been violated. The constant string conventions used to convey these levels are "MUST_VIOLATION", "SHOULD_VIOLATION", and "MAY_VIOLATION", in descending degree of severity.

Tests

Tests for this library are available in the spec/xapiValidator_spec.js file, and may be run by opening the spec/mocha_runner.html page or via command line tools.

Contribution

Community feedback, criticism, and collaboration are most welcome.

On the less-technical side, if an error message appears cryptic or unhelpful, please report it as an Issue and it should be addressed.

License

MIT License (C) 2013 Zachary Pierce, Measured Progress