Wednesday, August 1, 2007

What will it be? Resource or metadata. How to know the answer without asking (and looking dumb in the process)

Several proposals are being discussed in the HCLS community for the resolution of URIs that represent resources from URIs that represent metadata about those resources. One of the most touted proposals involves the use of the 303 redirect protocol to resolve a URI request. On the basis of the value of the content type in the request header, a URI request can be resolved to either streaming RDF/XML or a simple HTML page.

Consider a scenario from a recent publication. A request URI cannot distinguish between a web page of a person and the person himself. An example would be the URI which may resolve to either a Web page of Mark Wilkinson's or to Mark Wilkinson himself, who may be described by a set of RDF triples. Based on the specified content type in the HTTP request header, if it is set to "RDF/XML", the RDF page with the URI would be retrieved. Otherwise, if the content type is set to "HTML", the Web page with the URI would be retrieved. Note the substitution of the "rdf" and "html" terms in the path of resolved URI in place of the original "home" term, creating a URI hierarchy of sorts. This proposal again seems to be a temporary hack rather than a long term solution.

In contrast, the XSLT based approach discussed by InChi holds a lot of promise. Entire RDF pages can be translated into HTML pages for display on a Web browser while the triples are accessible in plain RDF format. This dovetails with the idea of abstracting the details of the Semantic Web away from the end user as discussed in my previous post here. No troublesome redirects here. And this came through the HCLS mailing list only this morning. Moral of the story: Never lose hope!