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Re: Are people really using Identity constraints specified in

• To: "Roger L. Costello" <costello@m...>, <xml-dev@l...>
• Subject: Re: Are people really using Identity constraints specified in XML schema?
• From: "Owen Walcher" <xpriori@o...>
• Date: Thu, 19 Aug 2004 10:42:42 -0600
• References: <200408191615.i7JGFTA05579@s...>

If I am in charge of managing the applications for this company, I would
rather make a change to a schema than to have to open up source, modify
variables, and then recompile just to enforce an age of 18, say, instead of
16.

I can make this change in one place (the XSD), and the next XML document
that comes in gets the new enforcement rule... seems like, from a developer
point of view, you would want to do as much as possible in the schema,
leaving the complex logic to the application (like we only process sub-par
loans on the third Wednesday of the month) that cannot easily be done in
Schema.

Owen

----- Original Message ----- 
From: "Roger L. Costello" <costello@m...>
To: <xml-dev@l...>
Sent: Thursday, August 19, 2004 10:15 AM
Subject: RE:  Are people really using Identity constraints
specified in XML schema?


> Hi Folks,
>
> Here are some thoughts:
>
> 1. Constraints on data are not equal to business rules.
>
> 2. Business rules change.  Constraints on data do not.
>
> 3. Constraints on data should be specified in XML Schemas.  Business rules
> should not.  Business rules should be specified in higher level
application
> code.
>
> Example:
>
> A company has employees.  The current company policy on the minimum age
> requirement is 16.  Should the company create an XML Schema that
constrains
> <minimum-age> to 16?  Or, should the company create an XML Schema that
> simply constrains <minimum-age> to an integer, and let applications higher
> up provide further constraints?
>
> Answers:
>
> - Mandating that the minimum age of an employee be 16 is a business rule.
> It is highly likely to change over time.
>
> - The value of the <minimum-age> must be an integer.  This is a constraint
> on the data.  It will not change over time.
>
> 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.
>
> Comments?
>
> How would you characterize the distinction between "business rules" and
> "constraints on data"?  /Roger
>
>
>
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• Follow-Ups:
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    • From: "Linda Grimaldi" <grimlinda@e...>
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• References:
  • RE: Are people really using Identity constraints specified in XML schema?
    • From: "Roger L. Costello" <costello@m...>

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