Re: Architectural Forms and XAF
[David Wang:] > > On a related topic, I'm also wondering about the health of AF - > > where does it stand now? I see a ISO/IEC 10744 document about it, a > > mention of XAF on Hytime.org, and a XAF site, but little else... [David Megginson:] > It's pretty-much dead in the water for now -- almost nobody uses AFs > or even bothers to defend them who wasn't part of the original DSSSL > or HyTime design process. It's a shame, because they were a nice > idea. I think any obituary for architectural forms (AFs) is premature, to say the very least. (David, you're pushing my buttons!) * The XML Mortgage Partners architecture is based on AFs. Last month it was adopted by the Mortgage Bankers Association of America. It's hard to imagine how more money could be depending on AFs. Through Fannie Mae and Freddie Mac, the mortgage banking industry holds the keys to the US treasury. The mortgage industry is large, complex, diverse, and constantly changing, so it's a showcase for the power of architectural forms as tools for keeping communications between business partners open, flexible, and yet completely and demonstrably reliable and independent of any one software vendor. * Several enterprise-internal systems are based on AFs. These enterprises are more competitive as a result. Most of them are not advertising the fact that they are using AFs. I leave it as an exercise for the reader to figure out why they are keeping it a secret. * The "Kona" HL-7 architecture was based on AFs. It's hard to see how the problem of interchanging medical records can be addressed in any other really practical way, and still remain vendor-neutral. * The current XLink spec, as revised, is very, very close to being an inheritable architecture. In fact, I can't think of any way it's not actually an inheritable architecture, except for the fact that the spec doesn't declare it in a way that anticipates and facilitates its use as one among many other inheritable architectures. Even so, just as in the ISO standard AF paradigm, the attributes do all the work, and, in practice, the actual tag names of XLink elements are irrelevant to the processability of their XLink-ishness. (The creation of the XLink spec is thus a repetition of the history of the creation of the linking facilities of the HyTime architecture: the need to make many kinds of links, even while they must all be reliably processable as XLinks, has once again inevitably led to the reinvention of AFs.) * The Topic Maps spec, which seems to be newsworthy these days, is an inheritable architecture. It's good that XLink has turned out to be a set of architectural forms, because XML Topic Maps (among many other applications) must inherit the extended XLink syntax and semantics. When business communities wake up to the fact that they must choose between ... (1) using AFs or (2) de facto ownership and control of their industry's B2B vocabulary by a single software vendor, ... AFs will be the rule, rather than the exception. AFs are, quite simply, the object-oriented way of supporting reliable, vendor-neutral information interchange. There is just no avoiding the object oriented paradigm; it offers too many advantages, and it saves too much money. In the long run, there is also no avoiding the requirement of industries to control the nature of their own lifeblood: the information that flows between business partners. The concept of AFs is not inherently bound to particular formalisms and syntaxes, although the only standard syntaxes (there are presently two, one for SGML and one for XML) are bound to the DTD formalism. AFs are all about hijacking arbitrary models of interchangeable information, using such models in an unbounded number of contexts, specializing them in validatable ways, mixing them together in arbitrary ways, and supporting them via re-usable engines. An XML Schema can as easily be hijacked as a DTD, even though XML Schemas are not designed to support that. For that matter, the DTD formalism wasn't designed to support AFs either, but all inheritable architectures are today formally expressed as DTDs. Indeed, many DTDs are being inherited without the knowledge or permission of their owners, much less any formal indication in the DTDs themselves that such hijacking is possible. Similarly, there is no way to prevent an XML Schema from being hijacked and used as an integrated set of architectural forms, any use of which can be validated against the constraints of that XML schema. Monopolistic software vendors hate AFs; AFs are inimical to their business models. If you only look at information that emanates from sources that are controlled by the software industry, such as the W3C, you won't find any mention of AFs. Indeed, the W3C leadership actively suppresses the AF paradigm, sometimes referring to a similar but less rigorous and reliable notion as "element templates". Thus, one could easily get the idea that AFs are dead. Indeed, there are quite a few people who would *like* the AF idea to go away, but in fact the applications of AFs are growing, and, from where I sit, it appears to me that the rate of the increase is growing, too. I often urge people who are interested in learning more about AFs to read chapters 9-11 of David Megginson's excellent book: Megginson, David. Structuring XML Documents. Charles F. Goldfarb Series on Open Information Management. [Subseries:] The Definitive XML Series from Charles F. Goldfarb. Upper Saddle River, NJ: Prentice Hall PTR, [March] 1998. Extent: xxxviii + 425 pages, CDROM. ISBN: 0-13-642299-3. Price: US $39.95. -Steve -- Steven R. Newcomb, President, TechnoTeacher, Inc. srn@t... http://www.techno.com ftp.techno.com voice: +1 972 517 7954 fax +1 972 517 4571 Suite 211 7101 Chase Oaks Boulevard Plano, Texas 75025 USA *************************************************************************** This is xml-dev, the mailing list for XML developers. To unsubscribe, mailto:majordomo@x...&BODY=unsubscribe%20xml-dev List archives are available at http://xml.org/archives/xml-dev/threads.html ***************************************************************************
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