Modern businesses require online multipart collaboration to efficiently service their clients, and this requirement forces them to allow collaborating businesses to access their data. The immediate consequence is that the collaborating businesses routinely combine (join) their data with data that belong to several other parties. At the same time, all of the collaborating parties legitimately pose access constraints and combination (join) constraints to all other parties for their data, in an effort to maintain the usability and collaborative force of information sharing.

Now here lies the catch: you may have access to more than what each collaborating party has allowed you to access, or conversely, ill-posed business rules from the parties may translate into the inaccessibility of useful combinations of data.

This fine paper examines in detail how a consistent group of access rules can be formulated for all parties, starting with the access rules that each party formulates for its own data. Several algorithms are developed in the paper to build the group of access rules and then check it both for consistency and enforceability (in the words of the authors, “the adequacy of the rules in answering the authorized queries”). The authors also address issues like algorithmic complexity and how to efficiently handle access rules that are dynamically granted or revoked by a collaborating party.

The subject is modern and well analyzed in this paper (which is slightly wordy at times). The reader needs to refresh his or her knowledge of relational algebra, graph theory, and relational databases in order to follow the reasoning with ease. The paper is a notable contribution to the literature on secure cooperative data sharing, and will be useful to relational database professionals, even though it has a strong theoretical character.