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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Fallacies of Validation ... RE: Are people reall
 From: Roger L. Costello [mailto:costello@m...] >Yesterday Len Bullard made a similar statement: >> ... most fundamental errors are ... to consider only a single schema. Even if one thinks it easier to manage a single schema, command and control in adaptive systems is distributed. A schema is a control. Sometimes it is useful to have one control: think old TVs with volume and channel selectors. Sometimes, to be flexible with respect to a variant environment, it is better to have multiple controls. Think of component stereos with equalizers, filters, etc. Rick J. nailed it: variant and invariant conditions. Just remember, this describes not only the system, but the hosting environment as well. A self-directed evolving system monitors changes in the environment and adapts to them. This is also known as event-based notification. > ... fall into the trap of thinking of THE schema and not > recognizing the system as a declarative ecosystem of schemas > and schema components. Not should, but can be and often is. If these are isolates, it doesn't matter much how singular or multiple they are; but when they are in an ecosystem, they typically overlap and exchange information, and adapt as a result. That is why the emphasis is on ecotonal relationships, eg., where tundra meets forest what species do we find. >It would be very useful if we could have a simple example that shows how >several schemas might be employed, rather than a single schema. Could >someone provide an example? Look at any large reporting system. You can build that up a large schema but given local variations, do you have sufficient power/force/authority to make them stick or will you be constantly adjusting them, loosening them, strengthening them, and how will you know which is the right thing to so? It is of little use to be aware of context unless you have some means to determine what is important in the context relative to the goals of the transaction. The example of the Draconian parse rule is a good one: in what situations should it be relaxed? >Len, I like the term you used, "declarative ecosystem". Could you elaborate >upon what this means? www.eco-online.com/pdf/infoeco.pdf It means declarative definitions that overlap in a dynamic messaging environment. It can be random and exhibit behaviors like Brownian motion, or aware and self- directed, or simply patterned. The essence of intelligence is not patterning but self-directed adaptation. An intelligent system learns. It not only has memory, it has a goal seeking behavior that can use memory to more efficiently select behaviors. It is not trapped in the past. It speaks the future into being. > ... most fundamental errors are to consider schemas only at the external > system junctions ... The problem of locale is that it is declared locally but might require global management. Think of the British mail system vs the American mail system. The American system is far more efficient. The British system is more colorful. It is easier to send mail in the US. Size matters. The Brits can use a system such as MI5; the Americans can't. The problem is the numbers of active interfaces being routed to one or a few receivers. Sometimes, a single schema suffices for the whole system. Sometimes, you needs lots of little ones. The reasons may be scale or legacy (the way in which it grew and the decisions made for local reasons forced to the top as global policy). The reality is that social decisions matter. We engineer to these until the system decides it can't afford that any longer. Then we see standards with teeth or small groups breaking off and creating keiretsu: think Intel + Adobe, or Sony + whoever. Should I use ArcXML because ESRI dominates the market and supports proprietary dialects, or should I work hard to get ESRI to support GML because my customer demands open standards? Should I slow the system down with XSLT? Should I use IE because MS won the desktop hegemony? I can't separate social rules from engineering fundamentals. I apply engineering fundamentals to implement social rules. No size fits all. len 
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