Maintenance of subjects over time as the names change.

When information is collected as is, as opposed to being organized in
advance, the names used to designate subjects show variations that
make it impossible to conform to the equation: "one name = one subject".
The constant change to documents that serve as input in the Tax Map
system (including IRS publications, instructions, forms, FAQs) makes
the maintenance of such a knowledge base a moving target. The problem
is even made worse because topics not only are acquired from the
bottom-up, but they undergo transformations, both automatic and manual
(by experts), in order to facilitate intelligibility for the end
users. At the end of the day, the names present in TaxMap differ
somewhat from the initial names as they occur in sources.

One of the basic requirements for the maintenance of this knowledge
base is that the origin of each of the names used be traceable,
even--and especially--if it has gone through a variety of
processes. After a period of trial and error attempts, the solution we
found is to maintain the database of names used for topics as a
network of interrelated information objects, in which all operations
on names are recorded. The "Data Projection Model", a generic
model for accountable information systems, serves as the conceptual
foundation for this application.