Update semantics for multilevel relations
نویسندگان
چکیده
In this paper we give a formal operational semantics for update operations on multilevel relations, i.e., relations in which individual data elements are classi ed at di erent levels. For this purpose, the familiar INSERT, UPDATE and DELETE operations of SQL are suitably generalized to cope with polyinstantiation. We conjecture that these operations are consistent (or sound) in that all relations which can be constructed will satisfy the basic integrity properties required of multilevel relations. We also conjecture that the operations are complete in that every multilevel relation can be constructed by some sequence of these operations.
منابع مشابه
A Novel Decomposition of Multilevel Relations into Single-Level Relations
In this paper we give a new decomposition algorithm that breaks a multilevel relation into single-level relations and a new recovery algorithmwhich reconstructs the original multilevel relation from the decomposed single-level relations. There are several novel aspects to our decomposition and recovery algorithms which provide substantial advantages over previous proposals: (1) Our algorithms a...
متن کاملThe semantics of an extended referential integrity for a multilevel secure relational data model
To prevent information leakage in multilevel secure data models, the concept of polyinstantiation was inevitably introduced. Unfortunately, when it comes to references through foreign key in multilevel relational data models, the polyinstantiation causes referential ambiguities. To resolve this problem, this paper proposes an extended referential integrity semantics for a multilevel relational ...
متن کاملThe Semantics and Expressive Power of the MLR Data
In this paper, we deene the Multilevel Rela-tional (MLR) data model for multilevel relations with element-level labeling. This model builds upon prior work of numerous authors in this area, and integrates ideas from a number of sources. A new data-based semantics is given to the MLR data model which combines ideas from SeaView, belief-based semantics and LDV model, and has the advantages of bot...
متن کاملSolutions to the Polyinstantiation Problem
What distinguishes a multilevel database from ordinary single-level ones? In a multilevel world, as we raise a user's clearance new facts emerge; conversely, as we lower a user's clearance some facts get hidden. Therefore, users with different clearances see different versions of reality. Moreover, these different versions must be kept coherent and consistent — both individually and relative to...
متن کاملOn Persistent Semantics for Knowledge
Katsuno and Mendelzon suggested eight postulates for characterizing the semantics of update where the principle of minimal change is embedded [Katsuno and Mendelzon, 1991a]. In this paper we propose a new method for knowledge base update based on persistence. We examine the relations between the two di erent update semantics by investigating the satis ability of Katsuno and Mendelzon's update p...
متن کامل