The main issues that need to be resolved before applying transaction concepts to advanced applications such as CAD/CAM are a transaction model with a suitable control mechanism, and a new data model;A complex object is modeled as an hierarchy of interfaces and an implementation. This structuring facilitates storage of multiple object version and their subsequent reuse in design databases. Other concepts needed for data modeling in design databases are implementation and instantiation which are supported by our model. One of the main issues in design environment is change propagation. Two techniques--parametric instantiation and conditional instantiation--are provided that will alleviate the problems associated with change propagation;The design transactions are composed of subtransactions which are managed by the site where the project transactions are executed. While access to the design objects are controlled by the access protocol based on locking, they are not necessarily two-phased--only the access to the composite object hierarchy are serialized by following a tree protocol. The design database manages and controls the top-level project transactions. Hypothetical transaction, allows designers to explore alternate designs that may not be appropriate for future use. Because it is envisioned that most of the transactions in design environments will be transactions of this nature, support for the hypothetical transaction is provided with little overhead. A mechanism for upgrading a hypothetical transaction to a regular transaction is also developed;The project transaction can be decomposed into a hierarchy of subtransactions that model the behavior of design environments more closely. Independent commit transactions are introduced to reduce the cost of aborting long transactions; communicating interfaces between parent and child to capture the effect of multiple request-responses observed between users and application. Client-subcontractor relationship models the behavior of a user transaction that can invoke multiple applications to work on the same data set concurrently. The protocols needed for maintaining the database consistency are also presented along with the proof of correctness;The proposed transaction mechanisms and the data model will support design databases that are used to store structural data
