Web services transactions require relaxation of isolation property in order to coordinate the long-lived transactions in which autonomous organizations participate. However, the relaxation can bring about dependencies among the transactions. In case that a transaction has to access intermediary results of other transactions, its completion depends on their execution results. Furthermore, a circular dependency may be built up among a group of transactions. This circular dependency may destroy serializability of transactions and result in inconsistent executions. However, existing researches do not consider the dependency problem. In order to address the problem, we propose a new Web services transaction model, called WT-Dependency Model (WDM), and a WT-Dependency Management System (WDMS). The WDM models the dependency among Web services transactions and further proposes the notion of universal transaction, a group of Web services transactions linked with the dependencies. Based on the WDM model, WDMS guarantees that all the participating transactions in a universal transaction is successfully completed or aborted by deferring the commitments of individual transactions. WDMS also automatically detects and avoids a circular dependency in a universal transaction with the token based deadlock detection algorithm. This dissertation describes the WDM model as well as the design and implementation of the WDMS.
