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Re: [xml-dev] RDF people, please define "surface syntax" and "concrete syntax"


On 2012 Feb 20, at 12:49, Costello, Roger L. wrote:

> I see usage of the terms "surface syntax" and "concrete syntax" in multiple RDF articles, e.g.,
>    The RDF graph syntax is in several important respects simpler than any surface syntax, 
>    and makes possible a very simple and straightforward - almost elementary - approach 
>    to some surface-syntactic issues which are notoriously troublesome to get exactly right, 
>    especially the issue of bound name scopes. [1]
> and
>    In this section we present an RDF concrete syntax for the rules. It is straightforward to 
>    provide such an RDF concrete syntax for rules, but the presence of variables in rules 
>    goes beyond the RDF Semantics. [2]
> Would someone from the RDF community please define "surface syntax" and "concrete syntax"?

Unless I'm missing a subtlety, I don't believe there's an important distinction being drawn here.

In the first passage you quote, the adjective 'surface' is merely reinforcing the sense that syntactical issues are second-order, or superficial, ones in RDF -- it's about the ideas, not the bytes on disk (that the 'F' stands for 'Framework', not 'Format', is one of the minor RDF epiphanies).  That said, one needs a way of writing the stuff down and exchanging it, so there's a need for _some_ syntax, and the "RDF/XML Syntax Specification (Revised)" <http://www.w3.org/standards/techs/rdf> is the (concrete) syntax that's been standardised.

I don't know if the list of standards on that page is in a deliberate order, but it's ended up in a rough importance order, and the RDF/XML syntax specification is well down the list.

That page does include a document which talks about 'abstract syntax'.  That's not particularly exciting, and is simply referring to an abstract mathematical syntax, which might be used in a formal specification setting, and is not closely linked to a syntax that might appear on-disk.

A parenthesis: the set of documents on that page suggests some of the barriers to broader understanding of RDF.  RDF is hugely simple and powerful, but it can't quite shake off its heritage of very formal ways of thinking and writing about things.

Best wishes,


Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK

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