RSS in Notation3: An Exploration in Changing Formats

The fast-changing nature of the Web ensures that new formats and systems are always developing. To create a system of vocabularies that have lasting value, it is important not to tie them down to any specific syntactical representation.

The Dublin Core, an international organization which designs metadata vocabularies, has created the Dublin Core Metadata Elements Set (DCES) which has this flexibility. The DCES has been used in many different formats, includng HTML meta tags, XML and RDF.

Because of the generality and format-independence of the DCES, it can be used in new formats that the Dublin Core teams have not even heard of. An example of this is the DCES' adoption on RSS. The RSS Working Group was able to use the clearly-defined semantics of the DCES in their application, while still remaining true to the DCES specification.

In addition to simply using the Dublin Core elements, the RSS team was able to add additional meaning to their specification by defining some of their new terms as based upon the basic set of Dublin Core terms. In their RDF Schema, they define several of their new terms as an rdfs:subClassOf an older Dublin Core term. This system of extensibility allows the creation new terms while still allowing older Dublin Core processors to understand them.

The RDF framework allows all of these many different vocabularies to be mixed almost seamlessly. In addition, it allows the Dublin Core to take part in the creation of new formats based on the RDF model. One of these is Notation3, a system designed to bring easy readability to RDF files.

Since Notation3 was based upon the RDF model, RSS and the Dublin Core are both able to be used in this new syntax without any additional guidance on how to use the terms in the new format. To see how this is done, look at the example: RSS in Notation3.

The ability to use these disparate systems together, without any additional input or coordination from their creators, yet still sustain the semantic integrity bodes well for the extensibility and flexibility of the Semantic Web. It seems likely that in the future we will see more of these flexibile systems being built and seamlessly working together.

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