: The validity of the information stored in a database may be guaranteed or not, according to the family of items which is considered. The information available in the database may be complete or not, as well, for a given type of items. The paper discusses how these forms of uncertainty can be represented in the framework of possibility theory, and how queries to a database where information is neither necessarily complete and nor valid, can be handled using possibilistic logic. One benefit of the possibilistic modelling is to allow for the use of graded levels of validity, and of graded levels of certainty that the information is complete. 1 Introduction The validity of the information stored in a database can be often asserted, but not always, depending on the reliability of the sources which are feeding the database. Dually, the information available on a given topic may be known as complete in the sense that all the true information pertaining to this topic is stored in the base, ...

A possibilistic framework for constraint-based metabolic flux analysis