[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: xml taxonomy
You are both right. To work at this problem, one has to start with XML 1.0. Then the infoset, then schematization. The notion of basing a system on well-formed strings doesn't begin with XML. The notion that a formal system must have passive meanings doesn't begin with relational databases. One might want to look at what is and is not formally expressible and by what forms (avoid the interpretation initially and just deal with the axioms and theorems). It isn't useful to attempt to prove XML is as expressive as a relational database. It can be useful to determine which kinds of theorems produce isomorphic meanings and those that can't. For that, you XSLT is useful For example, the object-oriented impedance mismatch is one. The rules for theorem creating don't enable attributes to have elements. So a transformation from object languages where fields have object can't be done by transforming fields into attributes. One has to transform the fields into elements at the higher level of the 'names'. The meaningfulness is determined by the isomorphism. XML can express a programming language, but the forms are restricted by the formal properties of XML 1.0. <aside>One of the reasons namespaces get a sense of revulsion is that they are a foreign system grafted into the grammar.</aside> XML is a formal system with provable properties given that XML 1.0 provides the rules and the syntax. I *believe* it is more expressive than a relational database but that this forces schematization to reduce the Boltzman entropy problem and in that way, is no different than the relational system. Rules is rules. len From: Simon St.Laurent [mailto:simonstl@s...] chiusano_joseph@b... (Chiusano Joseph) writes: ><Quote2> >one set might be xml with tags only - no attributes; another might be >xml that is constrained to two levels; etc ></Quote2> > >What value would there be to labeling these types of XML (e.g. >"attribute-less" XML, "two-level" XML)? This seems to me to be >something that can be better covered by an XML schema design (if we >are talking about schemas here) than a broad classification. IOW, an >organization/agency may decide for whatever reason that they want to >avoid the use of attributes. It also appears to me that the >combinations/permutations of the different aspects here can become >quite extensive and perhaps unmaintainable. I'm not sure I'd knock this so quickly - there's something interesting here. I suspect the math around this is already done, in the hedge automata work that's underneath RELAX NG's pattern approach. Exploring this formally might not be as difficult as you suggest. That said, I don't speak the math well enough to be able to say that for certain. ----------------------------------------------------------------- The xml-dev list is sponsored by XML.org <http://www.xml.org>, an initiative of OASIS <http://www.oasis-open.org> The list archives are at http://lists.xml.org/archives/xml-dev/ To subscribe or unsubscribe from this list use the subscription manager: <http://lists.xml.org/ob/adm.pl>
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