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On 10/5/05, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,
>
> [Thanks Len, you beat me to the mark.]
>
> Peter, you make a good point, an XML document that is purely transient or
> purely persistent is likely the exception; the common cases are XML
> documents that are a mix of transience and persistence.
>
> However, what I was trying to do was to explore the "space" of possibilities
> for XML usage. To put it into semi-mathematical terms, I want to define the
> "axes/dimensions" of XML usage.
>
> To summarize everyone's comments it appears that there are three
> "dimensions" to the usage of XML:
>
> 1. Persistent XML: the XML document is persistent. Applications operate
> directly on the XML document.
>
> 2. Transient XML: upon arrival at its destination the data may be
> transformed into some other format (language objects, relational database,
> etc) that applications work with.
>
> 3. Application XML: the XML document is the application.
> Question:
Umm, isn't that only two dimensions? Aren't persistent and transient
just points on a single temporal axis? (Which brings me back to my
question of when does a document change from being persistent to
transient or vice versa?) I think at best you can have a single axis
that measure the length of time for which the document exists. Still
not sure that this helps any, but lets continue...
>
> Does the usage (role) of an XML document influence its design?
>
> For example, are transient XML documents typically flat, whereas persistent
> XML documents typically nested?
>
> Peter, I am still struggling how to put into the above "space" your ideas on
> XML-and-UI. Your assertion is that the usage of XML is not a 3-dimensional
> space, but a 4-dimensional space?
It is?
> Can you characterize the fourth
> dimension?
Hmm, I'm not sure I'd really try to confine XML design patterns (least
of all usage) to any N dimensions. But continuing to play along, from
this discussion we could have axis of:
1) Document duration;
2) Degree of human involvement;
3) Degree of automated manipulation;
You have to separate the last two measures since they aren't mutually
exclusive, but to the extent you can determine you have more human
involvement with the XML then I'd suggest the more likely you want
some highly structured data format. If it's all automated
manipulation then denormalize as appropriate for the given application
domain.
Having made those decisions, we might get some rules on the type of
persistence mechanisms to use depending on the first measure, but I
can't really see anything other than a trivial influence on the XML
data model. I'd assert the other two measures are going to dominate
the design decisions.
--
Peter Hunsberger
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