HP Labs Technical Reports



Negotiation-Based Concurrency Control in Design Databases

Garg, Pankaj K.; Raghunathan, Arvind

HPL-92-141

Keyword(s):

Abstract: Design databases store information relevant to the design of engineered systems, such as aircrafts, software systems, automobiles, etc. Concurrent design allows several designers to access the design databases concurrently while cooperating on a design effort and maintaining the consistency of the data items. Concurrency control in traditional databases has been achieved by using some version of a transaction model with serializability as the main correctness criterion. However, serializability is not a suitable criterion for design databases because: (1) individual design transactions can be of long duration, making it undesirable to grant locks, and (2) aborted transactions involve losing the work of some designer. Recent approaches have addressed the above issues by weakening the correctness criteria for transactions. The protocol to ensure correctness of such transactions requires a validation phase before transactions are actually carried out. However, current protocols for transaction validation are non-optimal in the level of concurrency achieved. In this paper, we present a negotiation-based protocol to identify design change conflicts in the transaction validation phase. Our protocol will allow for more concurrency than the protocols suggested in the literature. The protocol is being implemented in a software engineering environment, and is illustrated in this paper with the use of a simple programming example.

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