Use of Tags

[Andy Dent]

At 4:43 +0800 20/4/99, Peter Wilson wrote:
>I see two competing ways of designing an xml document type:
>
>1. Extensive use of attributes with elements used for structured and
>repeating items.
>    <Invoice CustomerId=12345 Date=19991231>
...
>
>2. Extensive use of elements and almost no use of attributes:
>    <Invoice>
>        <CustomerId>12345</CustomerId>
>        <Date>19991231</Date>
...
>
>If you attempt to associate data types with entity data which is the
>better representation? I.e. is it easier to define that the  <Price>
>element has a PCDATA content which is a currency value or that the Price
>attribute has a currency value?

The path that Microsoft seem to be following with XML-Data is to use
elements and describe the schema in XML.

My single biggest problem with this is the reuse of elements within other
elements - you can't define an element with local 'scope'. What happens
when Amount is an i2 in one context and a float in another?

For this reason, people modelling UML mapping to serialisation in XML have
recommended use of attributes (your 1.) for the properties of an object.
The discussion page  http://www.oasis-open.org/cover/elementsAndAttrs.html
has a great link on this topic. I recommend reading all the links for a
balanced, and evolving viewpoint.

Andy Dent BSc MACS AACM, Software Designer, A.D. Software, Western Australia
OOFILE - Database, Reports, Graphs, GUI for c++ on Mac, Unix & Windows
PP2MFC - PowerPlant->MFC portability
http://www.oofile.com.au/

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