Dave Johnson on open web technologies, social software and software development
This is the closest thing to a blog post that I've written lately, a post to the OpenSocial specification group on aligning OpenSocial with RDF and Linked Data:
Link: RDF and OpenSocial
This is a topic of interest to me, so I'll try to elaborate.
First, I want to point out that RDF is not a representation, it's a way to model data and it's multiple ways to represent that data (in XML, JSON, etc.). I think the real question is: how do we enable OpenSocial to hook into the RDF-based web of "Linked Data" that is rapidly growing up around scientific data, government open data and the academic world. I'm not going to go into the benefits of Linked Data in this post, but I will disclose that I work for a company that uses RDF as a common data model to enable loosely coupled integration across our web application products (see also Jazz Integration Architecture  and OSLC ). We'd like to be able to integrate with OpenSocial services in the same ways.
I'll explain the basics of RDF. RDF is way to model web data and ways to represent that data in XML, JSON, Turtle, etc. The RDF data model is simple, we have resources identified by URIs and property values associated with those resources. Resources can have types, each type is identified by a URI. Property types have URIs too. Once you have defined your data model in terms of RDF types and properties, you can represent resources and their properties using RDF representations. There's RDF/XML for XML, there's RDFa for embedding properties in HTML. There's are JSON representations too, but not a standard for JSON yet.
So, to bring OpenSocial in-line with the world of Linked Data, we would define each class of OpenSocial objects as an RDF type, with a URI. We would define each OpenSocial property as an RDF property, with a URI. In some cases, we'll want to use existing properties, like the Dublin Core title, name, etc., and in some cases we'll want to define entirely new types and properties.
As a starting point, I think we would do the following:
* In OpenSocial v2, we would define all OpenSocial objects and properties as RDF types in the OpenSocial Specs. This means simply assigning a URI to every class and every property we define, using standard properties where appropriate and defining new ones as needed. Object and property names would rename the same and we'd have what is essentially an RDF mapping built into the spec. Existing OpenSocial representation formats would stay the same, but we'd add some new RDF representations.
* We'd introduce an optional new OpenSocial spec that services MAY implement: the OpenSocial RDF Specification. The specification would simply require that a service provide RDF representations of it's resources via content-negotiation. The service could offer RDF/XML or HTML with RDFa, JSON/RDF or all of the above.
That's a starting point and I think we could come up with some other ideas if we thought more about use cases. Anybody else interested in aligning the worlds of OpenSocial and Linked Data?
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