Schema.org as JSON-LD
Thus far we have discussed the use of the schema.org vocabulary to mark up webpages using microdata, though the same can be achieved using the RDFa syntax. Using either of these syntaxes to embed metadata in web pages makes sense where the information is primarily being delivered as human readable documents, with schema.org being used to help with the computer-facilitated discovery of these documents. However, at times when such information is being transmitted from one computer to another it is not necessary for it to be human readable. Examples would include creating a catalogue by harvesting metadata from several sources and providing metadata for programmatic access via an API. JSON (JavaScript Object Notation), and specifically JSON-LD (JSON for Linking data) is a format that is eminently suited to such use2.  Google supports JSON-LD for provision of schema.org metadata3 when embedded in webpages.   Some services go further and allow schema.org metadata to be provided as stand alone JSON-LD documents, an example of such a service is the Learning Registry4. The Learning Registry is a technical infrastructure for capturing, connecting and sharing data about learning resources available online. One advantage of storing schema.org metadata in stand-alone JSON documents is that it means that metadata may be provided by people other other than the maintainers of web pages about the resource being described.
