Multiple Semantic Web Languages (was: Re: reifying variables)

From: Sandro Hawke (
Date: 02/12/04

  • Next message: Peter F. Patel-Schneider: "Re: Multiple Semantic Web Languages"
    > I argued long and loud in the W3C WebOnt working group about problems that
    > using the RDF syntax caused.  This argument didn't go anywhere, so I gave
    > in and created a partial solution for OWL. 
    Do you remember why the WG disagreed with you?
    > > I've
    > > sometimes campaigned unsuccessfully for a standard meta-language, in
    > > which the syntax and semantics of practical data languages are
    > > described.
    > XML might be the syntax half of this.  Isn't model theory (or even
    > mathematics) the semantics half?  :-)
    Ah, I meant a machine-usable meta-language.  Like java byte code,
    XSLT, or prolog DCGs -- something you can use to define a new language
    such that computers can simply use the new language without human
    > > In any case, using an "RDF-Like" syntax is using counterfeit money and
    > > I suspect is only accepted as the price of admission by mistake.  I
    > > apologize for not noticing and commenting on SWRL doing this back in
    > > November.
    > There have been several proposals to make this sort of solution the
    > official one, including things like dark triples.
    "Dark triples" was proposed during a time when RDF Semantics were
    rather up in the air, I think.    It's less in-order now.
    > I would very much welcome a statement from W3C that Semantic
    > Web languages do not have to be written in triples (or quads, or quints,
    > ..., as in several recent proposals).
    The consortium doesn't have many ways to make statements like that.
    Maybe the closest would be in the charter of a new working group or
    activity.   In fact, the SWRL WG charter I floated a few months ago
    had some words about the extent to which the language needed to be
    based on RDF.
    What I had in mind were rules like in n3, of the form
         forall u1, u2, ...
            { rdf graph }
            exists e1, e2, ...
              { rdf graph }      
    where the rule itself did NOT have to be conveyed in RDF.  (I want
    them to viewable as RDF, and I believe it's possible, but we didn't
    want the WG to be forced to do that.)
    I was interested in seeing if the rule language would itself turn out
    to be a better RDF serialization language.   
    Had this been given to the membership, and had the membership approved
    it, I suppose you would have had much of what you want.
    In more general terms, I think what qualifies or does not qualify as a
    Semantic Web language is a complex social question.  What TimBL says
    in speaches probably counts for a lot, what the consortium members say
    in WG charters counts for a lot, but so does ... everything else.
    And cool, useful, deployed, working systems speak very, very loudly.
    > > You would agree there's a cost to each new language, right?  
    > No.  I do not believe that there is a net cost for most new
    > languages/representations.  New languages/representations are accepted in
    > part because of problems with existing languages/representations.  If the
    > new language/representation does not have benefits outweighing its costs,
    > it is unlikely to be accepted.
    You changed "cost" to "net cost".  Big difference.
    You're right about net cost; I was thinking about up-front costs or
    barriers to entry.  Every new language that agents (eg browsers) need
    to know makes the cost of developing a new agent higher.  But you're
    right that the market will decide and people will implement at least
    dozens of languages if the benefit is there.  And plugins help a bit.
    Part of the role of the W3C is to try to cut down the number of
    languages -- one scalable vector graphics language instead of four --
    to keep this up-front cost in check.    This is something software
    vendors and user communities really want.
    There are also costs to users of upgrading their software, and costs
    to developers of learning to use a new language.   There are great
    network effects when more and more people use the same language.
    Bookstores can label the shelf, instead of just having to hide the
    books on each little language in Miscellaneous/Oversize.  
    So I'm all for people competing with RDF/XML in the hopes they come up
    with something really better, but we should recognize that it's mostly
    a winner-take-all proposition, and we can't expect to let a thousand
    Semantic Web languages bloom (except via the meta-language approach,
    All of this is perhaps irrelevant to the original "reification of
    variables" question, since a logic language with its syntax encoded in
    RDF can hardly be said to be itself RDF.  It is its own language, with
    its own deployment and cost issues, even if carried on RDF/XML.  All I
    was saying was that IF you're going to encode the syntax for the
    language in RDF, for whatever reason, please encode it in real RDF
    (with real RDF semantics [plus iron]), not in an RDF-like language
    with insidious differences from the standard.
      -- sandro

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