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[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
 while i already have a stated position on the dangers of overly strict checking systems - i like to see easy to spot errors so i can get a measure of how many hard to see errors are in the system - i do think there is a very important and valid role for it systems to implement and enforce business rules. while this is not necessarily the same as constraint checking - indeed it can be much more complex - it is something that makes our systems more than just data/document repositories and number crunchers. i have any number of examples of where there has been a supposed system failure, only to find on investigation it has been a breaking of the business rules and the it system is the warning system to management that something needs to be investigated. rick Bullard, Claude L (Len) wrote: >Michael is right, but this isn't a one size fits all decision. >Loose filters allow dirt to seep into the system. The architectural >question is what are the right places to put such rules into >a system? We are aware of different technologies for this, >and it is a good thread to out the issues if that interests >the members of this list. > >That a technology can accomplish a task doesn't mean it >is the right tech for that task. It doesn't mean it isn't. >I suspect this is another task situatedness issue, but given >a services architecture, one might want to inquire about >tasks relative to their roles in distributed processes >that are candidates for orchestration. > >len > > >From: Roger L. Costello [mailto:costello@m...] > >Michael Kay wrote: > > > >>I tend to be a little wary of constraints myself. >>Many of those you see in student textbooks are >>misguided. If I see a schema (XML or RDB) with the >>constraint that employees must be over 16, I ask >>myself what the IT department would do if the >>business decided to hire someone under 16. If >>there's a rule that an employee's manager must >>themselves be an employee, I ask what would >>happen when someone is told that they now report >>to a contractor. >> >> > >This is excellent: > > > >>It's not the job of computers to limit what people >>are allowed to do (or the job of the IT department >>to regulate the business). >> >> > >The following innocuous sentence has profound implications >on the role of schemas: > > > >>A guideline I use is that constraints should be there >>only to protect the IT system itself from data that >>it cannot handle. >> >> > >Would you elaborate upon this sentence Michael? I believe >that you are saying that the role of a schema is to define >things such as: >- ensure that a "date" is indeed a valid date >- ensure that an "age" is indeed a valid age > >The role of a schema is not, for example, to specify: >- the "age" must be at least 16. > >So, your guideline says: use schemas to specify datatypes >for objects, not their range of values. Is that a fair >summary of your guideline? /Roger > > >----------------------------------------------------------------- >The xml-dev list is sponsored by XML.org <http://www.xml.org>, an >initiative of OASIS <http://www.oasis-open.org> > >The list archives are at http://lists.xml.org/archives/xml-dev/ > >To subscribe or unsubscribe from this list use the subscription >manager: <http://www.oasis-open.org/mlmanage/index.php> > > > begin:vcard fn:Rick Marshall n:Marshall;Rick email;internet:rjm@z... tel;cell:+61 411 287 530 x-mozilla-html:TRUE version:2.1 end:vcard 
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