Re: Use of XML ?

[Eric Bohlman <ebohlman@earthlink.net>]

8/1/01 8:27:08 AM, Caroline Clewlow <cclewlow@eris.dera.gov.uk> wrote:

>I'm involved in a project to exchange data between two seperate
>databases ...... and, in an attempt to use XML for data exchange we
>developed a schema, and parsed the data into XML before transporting it
>over to the receiving system - which in turn 'deparsed' the data into
>its own format.
>
>Whilst we were developing the system we came to the startling
>realisation that everything we were doing via XML could actually be done
>by simply making each side aware of the 'class' (using Java) of the
>object that the data is read into - in the same way that both sides
>would need to be aware of the schema. So rather than transporting the
>XML doc we could just send that object.
>
>We know we must be missing some fundamental point here - but if someone
>could just help by explaining why XML is so important as a data exchange
>format it would be very appreciated

Because not all cases of data exchange occur between systems over which one person or group has 
control.  In your example, the transport format is directly coupled to the internal representation 
the two systems use for their data.  That's all well and good if the same people implemented both 
systems, but it starts to break down if, say, one of the systems is implemented in Java and the other 
isn't.  XML comes into play when you want the transport format to be independent of the internal 
details of how the data is processed.  By adding an extra layer of abstraction, you decouple the 
exchange process from the internal implementation details.  There are cases where for performance 
reasons you may not want to do this, but you really need to think carefully about them.