Temporal data obsolescence: modelling problems

Data and knowledge bases model certain aspects of the world. When the state of the world changes faster than our ability to discover these state changes and update the data repositories accordingly, the confidence on the validity of data decays with time, and software systems running in such environments have to cope with the decay of confidence in the data lest they run the risk of giving wrong answers and behaving erroneously. This gradual loss of confidence in stored data is termed information obsolescence, and it is inherently a temporal phenomenon. We have come across such a problem when designing an information system for traffic monitoring and control in a large city, and investigate some problems related to this modelling task. We propose two approaches to deal with information obsolescence, the analytical approach and the algebraic approach, and show how both can converge to a general, temporal treatment of obsolescence. Our immediate goal is to try to approximate and reduce the whole problem of monitoring and controlling obsolescence of information to a purely temporal phenomenon, so that we can model the system using conventional temporal database technology.