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- To: "Thomas B. Passin" <firstname.lastname@example.org>, <email@example.com>
- Subject: RE: [xml-dev] Are people really using Identity constraints specified in XML schema?
- From: "Cox, Bruce" <Bruce.Cox@USPTO.GOV>
- Date: Fri, 20 Aug 2004 14:26:57 -0400
- Thread-index: AcSG40ZzgV+etDOuQGGM0Fy6JsXZJA==
- Thread-topic: [xml-dev] Are people really using Identity constraints specified in XML schema?
In my world, attorneys speak "business rules" and IT folk speak "data
constraints". Often, their intention and extension are identical. A
really good schema is the membrane where these two sets touch each
other, that is, it is equally successful from both points of view.
Bruce B. Cox
From: Thomas B. Passin [mailto:firstname.lastname@example.org]
Sent: Thursday, August 19, 2004 4:59 PM
Subject: Re: [xml-dev] Are people really using Identity constraints
specified in XML schema?
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)