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On Aug 24, 2004, at 12:25 PM, Bullard, Claude L (Len) wrote: > Some background: a public safety system can be seen > as multiple information ecosystems and technologies that > exchange information to prevent crime, solve crime, and > predict and mitigate incidents that threaten the public. > They can be ranked by their relationship to real time > events, aka, a Call For Service dispatched from a 911 > system (a call center). Once a CFS event is closed, > an incident is created in the police records management > system and/or the court systems. > Just curious ... hypothetically what could/should a public safety agency do with a CFS event that didn't conform to some future structural contract / schema that it was supposed to conform to? Obviously "nyah, nyah, invalid message, let the poor [expletive deleted] bleed" is not the right answer. On the other hand, letting the bug in somebody's procedures or code go un-reported is not a great idea either. I guess this echoes the eternal RSS/Atom debate over draconian error processing, and I suspect that all the myriad ways that RSS gets ill-formed in practice will be revisited as XML becomes pervasive in other situations. I'm thinking these days that schema validation has a big role to play in test-driven development but is of highly doubtful value in operational situations, or at least ones in which people can die or fortunes be lost if a message that is otherwise meaningful is rejected for "mechanical" XML reasons. Also, to address one of the issues that came up in this thread, I think that declarative vs procedural definition of the validation rules is a question that is orthogonal to this one. In general I agree with Roger's summary, but we can imagine "structural" constraints that could only be validated procedurally ['the value in field X must be a prime number' is the classic, if contrived example]. We can also imagine "semantic" constraints that could be validated with a declarative rule-based system, and anyway query languages such as SQL and XQuery seem to live in the fuzzy middle ground between declarative and procedural.
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