When researching into related work for Krextor, I discovered this paper about XSDL (XML Semantics Definition Language). (Note that by XSDL the authors do not mean the new name of W3C XML Schema, as the latter has only been renamed recently.) XSDL is a language that allows for solving very similar problems as Krextor – extracting RDF in terms of some ontology from XML documents. I had always been looking for a nice declarative way of doing so, and there it is.
I should have known earlier. I knew it earlier! This paper already existed in my document collection, added on 2007/08/08, and in my ever-growing to-do list there was a neglected entry “read documents added on 2007/08/08”!
For a moment it seemed to me that I had reinvented the wheel, but actually it’s not that bad. While XSDL has a solid formal specification (which Krextor does not have), it seems that it has never been implemented. Krextor has been implemented, as it emerged from a very concrete need to get a concrete task done, and it has been evaluated in various settings. Therefore, I can use XSDL as an inspiration w.r.t. the theoretical background and a nicer declarative syntax.