Demonstration of using json-schema for basic validation

[cmcavoy]

Built off of work from @ottonomy. Defines the badgeClass and badgeAssertion in json-schema. Basic test suite demonstrates using jjv to validate against the schemas.

If all this looks right, I'd like to take a stab at moving openbadges-specification to a module that exports these schemas, then refactor openbadges-validator to use these schema and jjv for the first level of validation.

[kayaelle]

This is looking great. I think we may want to add more specifics to the string types. For instance:

"evidence": {
        "description": "URL of the work that the recipient did to earn the achievement. This can be a page that links out to other pages if linking directly to the work is infeasible.",
        "type": "string",
        "format": "uri"
  }

  "issuedOn": {
        "description": "Date that the achievement was awarded.",
        "type": "string",
        "format": "date-time"
      },

Although don't think the above covers unix timestamps original was: ["string", "number"]

[ottonomy]

Thanks for pulling this together and distributing it with such an easy testing system.

Based on the Understanding JSON Schema book that Jason Lewis sent me, I have worked up a version of the badgeClass schema that packages a bunch of OBI object definitions inside a "definitions" object at the top level of the schema and then references those definitions, separating definition from structure a little bit.

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "definitions": {
        "ImageDataUrl": { 
            "type": "string",
            "pattern": "^data:(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$"
        },
        "BadgeImage": {
            "oneOf": [
                { "$ref": "#/definitions/ImageDataUrl" },
                { "type": "string", "format": "uri" }
            ]
        }

    ...

    "properties": {
        "image": { "$ref": "#/definitions/BadgeImage" }

    ...

It took me a long time because I couldn't get it to validate with jjv or get any useful error messages out of it. Switched over to using JaySchema, and it started working. See my branch at: https://github.com/ottonomy/openbadges-discussion/tree/cmcavoy-schema/openbadges-assertion-schema ( badgeClass schema | corresponding test file )

The definitions block in the schema is a little bloated because the first path I was trying was to see if we could mash together the schemas for all three OBI objects (Assertion, Badge Class, and Issuer Organization) into one schema. I was trying to get them using shared definitions, referencing each object's schema as "https://badgealliance.org/standard/1.1#/badgeClass", but I couldn't get that approach to validate -- the $ref's to definitions got lost.