A belief-consistent multilevel secure relational data model

摘要

Multilevel relations, based on the current multilevel secure (MLS) relational data models, can present a user with information that is difficult to interpret and may display an inconsistent outlook about the views of other users. Such ambiguity is due to the lack of a comprehensive method for asserting and interpreting beliefs about information at lower security levels. In this paper we present a belief-consistent MLS relational database model which provides an unambiguous interpretation of all visible information and gives the user access to the beliefs of users at lower security levels, neither of which was possible in any of the existing models. We identify different beliefs that can be held by users at higher security levels about information at lower security levels, and introduce a mechanism for asserting beliefs about all accessible tuples. This mechanism provides every user with an unambiguous interpretation of all viewable information and presents a consistent account of the views at all levels visible to the user. In order to implement this assertion mechanism, new database operations, such as verify true and verify false, are presented. We specify the constraints for the write operations, such as update and delete, that maintain belief consistency and redefine the relational algebra operations, such as select, project, union, difference and join.