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Subject: Re: [relax-ng] close schema language
David RR Webber - XMLGlobal wrote: > Message text written by Eric van der Vlist > > Schematron is the only language I know where "everything which is not > forbidden is allowed", the main principle of the other languages being > rather that "everything which is not allowed is forbidden" which, by > itself, is "closed". > <<<<<,<'' > > Eric - excellent points. Thanks! > > Having worked for many years in Prolog - there's another facet to > this declarative / assetive world which can be fun - ie - somethings > that you never even realized can also be allowed - together. > > It teaches you that you must always explicitly assert the > "Otherwise - do nothing" facts - which is definately a good habit > to get into. > > Java - throw / catch users note - weird behavioural treatment of > fringe error conditions relates!! Yes. There is a difference, though between a schema language (especially when it is used to validate documents) and a development language and I think that most of the people see a XML schema as a kind of firewall which will protect them from the unexpected -these "otherwise" facts-. Foreign namespaces (and "open" schemas in general) are then seen as potentially dangerous since it's like removing a part of the firewall exposing the applications to more unexpected facts and requiring a different design. Among the RSS 1.0 Working Group, for instance, everyone agreed to accept foreign namespaces elements, but the majority decided to accept them only when the content model (simple/complex) was not changed showing that the notion of open/close is relative ;=) ... Eric -- Rendez-vous à Paris pour le Forum XML. http://www.technoforum.fr/Pages/forumXML01/index.html ------------------------------------------------------------------------ Eric van der Vlist http://xmlfr.org http://dyomedea.com http://xsltunit.org http://4xt.org http://examplotron.org ------------------------------------------------------------------------
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