[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Are people really using Identity constraints specified in
There are public safety systems, eg, court systems, that rely on RuleML as a means. Essentially, where ever you might use a human expert, you can apply a rules base (expert system) if you can acquire and maintain the rules cost effectively. That is why some see the Semantic Web as a means to improve the performance of lawyers. len -----Original Message----- From: Cox, Bruce [mailto:Bruce.Cox@U...] I have not been making the same distinction between syntactical/structural and semantic/business rules in this thread that Michael has below. To me, a business rule is one that came from the lawyers, not from IT, which can be syntactical/structural; and from IT, the rules are sometimes semantic (which I take to mean not so readily amenable to automatic checking). It seems more likely that there is a continuum of rules from the one extreme to the other, which might be sorted into layers where convenient for understanding or implementation. I think I prefer the declarative approach to specifying rules, on the assumption that these can be more reliably exchanged and implemented by different systems. A fortuitous choice of layers would be those that are supported by standardized vocabularies for declaring the rules. In that regard, have any of you looked at the RuleML stuff? (http://policy.ruleml.org/ and http://www.ruleml.org/) Is any of that useful in this context? Bruce B. Cox SA4XMLT +1-703-306-2606 -----Original Message----- From: Bullard, Claude L (Len) [mailto:len.bullard@i...] Sent: Monday, August 23, 2004 10:03 AM To: 'Michael Champion'; XML Developers List Subject: RE: Are people really using Identity constraints specified in XML schema? In a one way flow to a source, the business rules can be concentrated in the back end fairly successfully. In a blind exchange between potentially hundreds, thousands, or millions of actors/services, this doesn't work. Without the application design properly scoped, one can't make the rules of thumb work. That is what scaling is all about. As the number of service peers goes up, one might want to actually increase the work done by the schema, but at some point, one will hit a boundary, eg, cultural, legislative, etc., and it will throw an exception. Exceptions are not errors. They are feedback. One does not measure to manage; one measures to improve. len From: Michael Champion [mailto:mc@x...] On Aug 23, 2004, at 9:05 AM, Roger L. Costello wrote: > > > Would you mind elaborating more upon what you see as the role of > validation? Should there be levels of validation as I suggested last > week? Or perhaps you are suggesting that there should be no > validation? > I'm not the Michael you asked to respond, but here's the way I see it. "Syntactical" or "structural" validation of the sort that Schemas, XForms, or client-side Javascript do has a role in eliminating a certain number of mechanical data entry errors, such as leaving out required items or not putting numbers in fields that require numbers (e.g. phone numbers, dates, etc.) XML schemas (of one sort or another) are potentially useful ways to define such constraints, although as Michael Kay's anecdotes remind us, this is hard to do in a culture-neutral way, e.g, US postal codes are all numeric, most other countries' are not. But this is at best a rough check on "validity" in some business sense. "Semantic" or "business rule" validation, on the other hand, essentially cannot be done without accessing a database / knowledge base to make sure that the request being made can be fufilled. An obvious example is credit card validation, and for a variety of technological and security reasons it is going to be done towards the back end of a dataflow. Trying to force-fit this into schema validation seems more or less hopeless. One question I've always had is whether it makes sense to bother with the structural validation if you are going to have to do the business rule validation anyway. It comes down to a design decision -- since it's generally cheaper to recover from errors detected earlier in the process than later, if you can catch them early with schema validation, go ahead. But if that is going to be harder to do than it is worth, e.g. making the data entry screen understand the co-occurrence constraints between a country code and the format of a postal code, I'm not at all sure why one would bother.
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|