More thoughts on invoices

In addition to a "brittle" definition of a specific data structure representing an invoice, a semantic programming system should have some general, dare I say semantic knowledge concerning invoices, and business processes in general, documents, and so on. In other words, there should be a semantic web, one view of which might be a specific data structure definition, and the system could interact with e.g. Perl code using that specific data structure definition - but it could also modify it based on what it knows about invoices.

That's pretty darned hand-wavy, but again: it's where I want to go.