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Roger L. Costello wrote: > - The value of the <minimum-age> must be an integer. This is a > constraint on the data. It will not change over time. Ha! What happens when the government decides that some relevant age is 67.5 years instead of 67? > Therefore, an XML Schema should simply constrain <minimum-age> to be > an integer. Higher level applications should implement the business > rule that <minimum-age> be further constrained to 16. > > How would you characterize the distinction between "business rules" > and "constraints on data"? A tricky, tricky issue - what is or is not a "business rule". I suspect that in practice most constraints that are not business rules are in place for supposed programming reasons, or by force of habit. In one project I work on, we have a data type that is a union of 1) an enumeration of strings, 2) a string that follows a certain regex pattern, and 3) an integer constrained to a certain range. No, don't bother to ask - it's one of those multi-agency reconciliations. -- Thomas B. Passin Explorer's Guide to the Semantic Web (Manning Books) http://www.manning.com/catalog/view.php?book=passin
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