Thanks everyone for this thread, its very interesting.
What is a projection of what, and What is modeling what is fascinating - not only in the markup and computer modeling world,
but in physics as well. Richard Feynman had a great chapter in one of his books about the physical universe seemingly designed specifically to maximize the
number of equally valid but distinct models - So when I hear people claim we are not modeling "the real world correctly" it does make me chuckle a bit inside ... not in pejorative way, just that the whole concept of modeling "the real world" is a funny thing
as it is.
But back to computers ....
First trees vs Graphs. I can see arguments both ways ... and other ways. Trees and Graphs arnt the only models. No model is "right" ... but is it "useful"
? Thats a useful question (self-referential reference intended).
Projections of a core data model is intersting. For example I am currently trying to imagine whether it makes sense to take the UBL messaging model and use
the actual messages as the data store and model business transactions directly as a revision chain of message documents. Or does it make more sense to model the underlying business model different and "map" the messaging model at the fringes ... Neither
of these are "perfectly right" ... but there is a compelling elegance to imagine the messages as the actual model itself.
With the right views, the right (or "good enough") technology, is it possible to not care which is the model and which is the projection?
The same as with physical systems where you can model the system as the set of interactions instead of the set of states ...
can you model a business process solely as the set of messages and the interactions they have with each other ?
Is a particle just a transient stable state between two different energy states ? Or are the energy states the projection of a change of state of particles
? Which is real and which is a projection? Both ? Neither ? does it matter ? Is a "Shipment" really the stuff in a truck ? or is it the set of messages and contracts which constrain the business ramifications of items leaving one organization's ownership
and entering another's ?
I suggest what's "real" is not so important as whats useful.
Trees are definitely useful.
Now if only money would grow on them :)
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David A. Lee
