XML vocabulary for expressing constraints?

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

Hi Folks,

When I fly from Boston to Washington D.C. on Southwest airlines, I sure hope the airlines have coordinated with each other and there isn't, say, a United airplane that will be at the same route point at the same time as my Southwest airplane.

Identifying conflicts is important.

My example is one of identifying conflicts among geometric shapes: we can represent the route of the Southwest airplane as a set of shapes (cylinders, spheres, points, etc.) and we can similarly represent the route of the United airplane. Then we can do some math and determine if there are any conflicts among the shapes. 

3-D shapes are not the only things that can have conflicts. Suppose Southwest has an airplane available from 0800 to 1600 on Friday and someone needs an airplane on Friday between 1000 to 1300. That's an example of a conflict: is there an overlap between an airplane's availability and the need for an airplane. However, unlike the previous example, there are no geometric shapes involved in identifying this conflict. (Also, in this example conflict is a desired thing whereas in the previous example conflict is an undesired thing.)

So the two examples seem to be quite different: the first involves identifying conflicts among geometric shapes and the second involves identifying conflicts among resource availability and resource need.

But surely there is a common thread that ties them together? After all, they both involve identifying conflicts. So what is the common thread that ties them together? 

...... I have learned that what I describe above are instances of Constraint Satisfaction Problems (CSP).

So, I would like to express my constraints in XML and feed the XML into a CSP tool. Has anyone created an XML vocabulary for expressing constraints?

Thanks!

/Roger