Re: [xml-dev] The privilege of XML parsing - Data types, binary XML and XMLpipelines (LONG)

["Roger L. Costello" <costello@mitre.org>]

Hi Sean,

> 2. Applications come and go but data lives forever (or can do). The
> trick of making your data outlive your applications is to divorce
> application-level data models from the XML. Burying data model
> information into the XML binds the XML to the application in a way
> which will bite when the application is changed or retired.
> 
> 3. Doing so significantly increases the semantic consensus required by
> communicating processes to share data. The beauty of *HAVING* to
> create your own data model[1] from a stream of Unicode with angle
> brackets is that you do not have to share any semantics or
> expectations other than Unicode with the originator of that XML. Far
> from being a burden, it is a *privilege* to be able to parse the XML
> and treat the data the way you want to, rather than have a data model
> imposed on you.

I passed your message along to a colleague.  Here are her comments:

XML is a syntax.  It has no data model.  So how would one "bury a data
model" in it even if one wanted to?   

Saying: 

    <foo>
        <bar>10</bar>
    </foo> 

does not tell me anything about the semantics of foo, bar, the
relationship between them, or their relationships with '10'.

If the producer and the consumer share no semantics then it is neither a
"burden" nor a "privilege" but rather a completely pointless act.   If a
meterological reporting station reports

    <weather>
        <temperature>60</temperature>
    </weather>

and I choose to interpret that as "my aunt betty just got a new puppy",
then the fact that some data was exchanged at all is completely
meaningless.