[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Syntax versus Semantics (was:"vocabulary constraints" and
RDF, or RDFS/OWL if you prefer, does no more than manipulate the labels we use for concepts. Machines don't check meaning, they check the labels and their combinations based on the rules we've set. But I don't agree with Roger's definitions, either. If syntax can be checked by machine, why should it have to be convenient? Some long-standing mathematical conjectures have been proven in the past few years solely by virtue of brute-force computation impossible before today's machines were available. Deep Blue as well won by brute force against Kasparov (who, I'm told, said, "but Deep Blue didn't *enjoy* winning"). I agree that "semantics" is overloaded and differently so in different contexts. There are those operations that 1) cannot be performed by machine, there are those operations that 2) can but aren't performed by machine (it isn't economical, or we haven't figured it out yet), and there are those operations that 3) are performed by machines. The boundary between 2 and 3 is a territory in dispute with daily skirmishes on several fronts where there are clear winners on one side or the other, but with no end to the overall conflict in sight. I think the best we can expect is a certain equilibrium between what machines can profitably perform and what humans will profitably perform (Len's social contract). The disputed territory moves across the landscape, but never completely disappears. Semantic web? Tanks and very long guns ended trench warfare, but they didn't end human conflict. Every new technology that makes it possible for some process to (at last) be performed by machine ultimately exacts a toll on human behavior: we have to follow the rules as well. If we don't, the context that makes the machine processing possible and comprehensible to humans is absent and the output the machine produces fails to meet expectations. When we first introduced XML for the detailed description of an invention, even those few applicants who whole-heartedly adopted it often failed to correctly populate certain key elements. Now, the description is submitted in PDF. At least it isn't on paper. In Japan, on the other hand, XML in patent applications is a resounding success. In this case, the difference is entirely cultural. Bruce B Cox Manager, Standards Development Division USPTO/OCIO/SDMG 571-272-9004 -----Original Message----- From: Dan Brickley [mailto:danbri@d...] Sent: Sunday, March 01, 2009 9:33 AM To: Costello, Roger L. Cc: 'xml-dev@l...' Subject: Re: Syntax versus Semantics (was: "vocabulary constraints" and other constraints On 1/3/09 14:03, Costello, Roger L. wrote: > 1. If something is in the realm of "semantics" does that mean it can only be processed by humans (eyeballs)? It cannot be processed by machines? [...] > WHAT IS SEMANTICS? > > Something is semantics if it cannot be simply specified in a declarative manner or it requires procedural code to express it. Some aspects of meaning can be made quite readily machine-checkable. If you say something is a Person, and if you use vocabulary in which Person and Document are disjoint classes, don't in the same breath ascribe properties to that thing which imply it is a Document. Machines can spot when you do this, even with simple RDFS+OWL schemas like FOAF. They can figure out, "hey, no true description of the world could ever fit this picture, what's up?". If you are working with RDF (RDFS/OWL) content, and the only rules you have are RDFS schemas and OWL ontologies, then you're pretty much limited to this kind of checking. However there are many more ways of screwing up in data, whether or not in RDF(expressing falsehoods, being incoherent or unintelligible or boring or vague), beyond contradicting yourself. For RDF, we can build machine-friendly checkers for some of this directly top of the RDF/OWL layer either directly in a query language (eg. SPARQL) or indirectly by generating the SPARQL from OWL plus some unwritten assumptions. Some trails back to 2001 here... and Schematron-inspired RDF work on expressing integrity constraints: http://www.xml.com/pub/a/2001/02/07/schemarama.html http://ilrt.org/discovery/2001/02/schemarama/ http://isegserv.itd.rl.ac.uk/schemarama/ http://danbri.org/words/2005/07/30/114 also http://clarkparsia.com/weblog/2009/02/11/integrity-constraints-for-owl/ http://jena.sourceforge.net/Eyeball/ Note than in RDFland, folk sometimes talk about its graph data model as a kind of abstract 'syntax'. Especially OWL people lately. I don't expect terminologies here to ever fully converge, too many compsci, engineering and other traditions are jumbled up together when they meet Web standards. cheers, Dan -- http://danbri.org/
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