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   RE: [xml-dev] XPath 1.5? (was RE: [xml-dev] typing and markup)

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At 10:45 AM 5/7/2002 -0400, Elliotte Rusty Harold wrote:
>At 3:26 PM +0200 5/7/02, Matthew Gertner wrote:
>>  I can
>>certainly say from my experience programming in Java and C++ that I would
>>prefer for a number to be a number and for a date to be a date, rather than
>>having to constantly convert back and forth.
>You're assuming that everyone agrees with you on what a date is, and what 
>a number is, and so forth. If you think about it, I suspect you'll realize 
>that's not true. Is a number floating point or integer? What are its 
>maximum and minimum values? Does a date type include dates after 10000 CE 
>or before 1000 CE? Strings are reasonably portable. Dates and numbers 
>aren't in practice. The local type I want to use may not be the type you 
>want to send. XML lets us talk to each other in spite of that.

Yes, and a query language that uses the types in the XML view can operate 
on a wide variety of data without worrying about the details of the 
original data sources. Note that XML Schema supports these distinctions - 
floating point, integer, maximum and minimum permitted values, the 
representation of dates, etc. The fact that we have a portable way of 
representing data types that answers these questions allows 
system-independent processing of a wide variety of data.

>The schemas data types spec tries to address these problems by being all 
>things to all people, but not all environments can handle integers that 
>can exceed a googoolplex or dates that precede Julius Caesar. Your date 
>type and my date type are not necessarily the same thing. Your number type 
>and my number type are not necessarily the same thing.

But a more limited form of date or integer can be defined in XML Schema, 
and used to represent integers in a system that can only handle, say, 16 
bit or 8 bit integers.



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