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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Are we losing out because of grammars?
 Marcus Carr wrote - > > Eric van der Vlist wrote: > > > Looks like we are going towards 4 different types of XML "schema" > > languages to define: > > > > - The structure > > - The datatypes > > - The rules > > - The semantic. > > This is very interesting - I wonder if we might be heading for another split > such as the one that saw XSL split into T and FO? The differences are > becoming more pronounced, and the term "schema language" is starting to lack > definition as a result. > > Eric (or anyone else), how do you differentiate between rules and semantics? Yes, it's really interesting to think about what "semantics" is supposed to mean, isn't it? I'm going to suggest that almost all computerized data processing occurs at the syntax and rules level, with virtually no "semantics" involved. Consider an sql update query. It has to follow a certain syntax. There are also some rules that are understood somehow. The database system also has some rules to follow that the query itself does not contain and that the query writer may or may not have taken into account 0f - like data integrity rules, or other stored procedures that get triggered. There is no "semantics" involved. I think that in such cases, when we say "semantics" we mean that a human who undertands the domain has written rules and database structures to help cause the 'right" things to happen. But the computer system only knows the syntax and the rules. Now, if a computer system may be asked to choose between several courses of action based on some other information, perhaps it might mimic what a human would do in this case. Then would we be entitled to speak of "semantics"? It seems that "semantics", at least in these applications, might consist of choosing sets of rules, and maybe even syntaxes, based on other information which we might call a "context". Of course, choices like these might be considered to be the result of applying higher order rules, but still, additonal information is needed. In this way, "semantics" is certainly a "higher" level layer than syntax or rules. As such, it doesn't seem to be a subject for schemas per se. Two questions arise - 1)Is this a useful view of "semantics" - that it is a means to choose between various sets of rules or perhaps syntaxes? 2) Do the systems people are envisioning need such a capability? Cheers, Tom P 
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