[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: [permathread:semantics] What Markup Is For
[Jonathon Borden] >I assume you are saying that XSD can do -without- types, and to the extent that XSD is used as a language >to express -syntactic constraints- on unicode strings, this is certainly true. The point of semantics is that >now that we have a piece of XML that let's say corresponds to some RNG pattern or XSD type _now what_. >How can we specify how different programs i.e. processes might use this piece of XML in an >interoperable fashion. The key word there is "processes". For specific processes to interoperate we may want higher order labelling (i.e. types) than UnicodeWithAngleBrackets provides. But - and I think this is the key point - those labels will be specific to the interoperability needs of specific processes at a point in time. They do not need to be innate in the XML itself. Indeed, putting them there reduces the usefulness of the XML. For example, what happens when we want to change the processes? If we tightly couple process-specific labelling into the XML, we need to revisit the XML. If however, we loosely couple process-specific typing as a downstream process from the UnicodeWithAngleBrackets, we can tweak the process-specific "object models" or "data types" or whatever they are called without revisiting the XML. We only need to revisit the XML if we need something not already represented in the XML. In my experience, this is a really useful level of loose coupling which has saved me countless programming hours. Its weird, XML is mentioned as a key technology in the whole loose coupling, web services, service oriented architectures thing and yet boxed XML[1] tightly couples things (like typing) in a counterproductive way. Sean [1] http://lists.xml.org/archives/xml-dev/200301/msg00396.html http://seanmcgrath.blogspot.com
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