A cooperative transaction model

Database interactions in engineering applications are very different from those of classical applications. One key aspect of these engineering transactions is their correspondence to interactive design activities. Designers want to work together, interact with each other, see someone else´s intermediate results and so on. The author presents a transaction model that is designed to support this cooperative work. The model is intended to be as orthogonal as possible with respect to the data model. The explicit knowledge represented in the hypotheses associated with the objects manipulated in a transaction is used to augment concurrency and to express a compromise after the negotiation between several conflicting transactions. Furthermore, when a transaction acquires some new knowledge it can dynamically change its hypotheses without waiting for a conflict being created