[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Using the concepts of Category Theory to create betterXML
Coincidentally I recently learned about category theory myself. Looking over your PDF, I don't think this says anything relevant about XML or XSLT. You're describing a very, very limited subset of XML documents that doesn't match anything I see in the real world. What this is describing is a very limited data model that happens to be encoded in an XML format; but that data model is in no way limited to or intrinsic in XML. Everything you say here could be said without any reference to XML, nor does it seem that this approach illuminates XML. At its base, your analysis makes one of the most common and fundamental mistakes I see in the literature. It attempts to define XML as just like some other well-known field (Pick your poison here: objects, relational data, tables, categories, HTML, etc.) rather than meeting it on its own terms and analyzing what it itself is. If I may quote from one of my own books, with apologies to John Godfrey Saxe: One night five developers, all of whom wore very thick glasses and had recently been hired by Elephants, Inc., the worldâs largest purveyor of elephants and elephant supplies, were familiarizing themselves with the companyâs order processing system when they stumbled into a directory full of XML documents on the main server. âWhatâs this?â the team leader asked excitedly. None of them had ever heard of XML before so they decided to split up the files between them and try to figure out just what this strange and wondrous new technology actually was. The first developer, who specialized in optimizing Oracle databases, printed out a stack of FMPXMLRESULT documents generated by the FileMaker database where all the orders were stored, and began poring over them. âSo this is XML! Why, itâs nothing novel. As anyone can see whoâs able, an XML document is nothing but a table!â âWhat do you mean, a table?â replied the second programmer, well versed in object oriented theory and occupied with a collection of XML documents that encoded UML diagrams for the system. âEven a Visual Basic programmer could see that XML documents arenât tables. Duplicates arenât allowed in a table relation, unless this is truly some strange mutation. Classes and objects is what these document are. Indeed, it should be obvious on the very first pass. An XML document is an object and a DTD is a class.â âObjects? A strange kind of object, indeed!â said the third developer, a web designer of some renown, who had loaded the XHTML user documentation for the order processing system into Mozilla. âI donât see any types at all. If you think this is an object, then itâs your software I refuse to install. But with all those stylesheets there, it should be clear to anyone not sedated, that XML is just HTML updated!â âHTML? You must be jokingâ said the fourth, a computer science professor on sabbatical from MIT, who was engrossed in an XSLT stylesheet that validated all the other documents against a Schematron schema. âLook at the clean nesting of hierarchical structures, each tag matching its partner as it should. Iâve never seen HTML that looks this good. What we have here is S-expressions, which is certainly nothing new. Babbage invented this back in 1882!â âAn S expression?â queried the technical writer, who was occupied with documentation for the project written in DocBook. âMaybe that means something to those in your learned profession. But to me, this looks just like a FrameMaker MIF file. However, locating the GUI is taking me awhile.â And so they argued into the night, none of them willing to give an inch, all of them presenting still more examples to prove their points, none of them bothering to look at the othersâ examples. Indeed, theyâre probably still arguing today. You can even hear their shouts from time to time on xml-dev. Their mistake, of course, was in trying to force XML into the patterns of technologies they were already familiar with rather than taking it on its own terms. XML can store data, but it is not a database. XML can serialize objects, but an XML document is not an object. Web pages can be written in XML, but XML is not HTML. Functional (and other) programming languages can be written in XML, but XML is not a programming language. Books are written in XML, but that doesnât make XML desktop publishing software. XML is something truly new that has not been seen before in the world of computing. There have been precursors to it, and there are always fanatics who insist on seeing XML through database (or object, or functional, or S-expression) colored glasses. But XML is none of these things. It is something genuinely unique and new in the world of computing; and it can only be understood when youâre willing to accept it on its own terms, rather than forcing it into yesterdayâs pigeon holes. -- Elliotte Rusty Harold elharo@ibiblio.org
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