Transaction management in databases supporting Web-based negotiations

Majority of systems supporting negotiations and collaboration between users require functions provided by database management systems, e.g. data persistency, concurrency control. In order to be used as kernels of negotiation systems, databases require however important extensions, reflecting the specificity of human interaction. The classical database paradigm assumes that database users communicate only via committed data. Since the users are totally isolated by the database system, each of them has an impression that the system is dedicated to him. When users collaborate to achieve a common goal, this approach is obviously too restrictive. Collaborators have to communicate directly before they agree on a data value. In the paper a particular approach to transaction management in databases supporting negotiation is proposed. It is based on a new transaction model that allows practically unrestricted collaboration among members of the same team. The basic assumption of this model is that negotiating users try to solve their access conflicts at a higher level than the level of the database management system. In case of potential access conflicts, the database system triggers a particular notification mechanism that starts negotiations between respective users at the application level. Since the proposed approach was practically verified, the paper presents also the Agora prototype. Agora is a Web-based conferencing system, offering conference participants flexible tools for collaborative work, in particular for flexible and efficient negotiation. Agora also contains a component, which facilitates collaborative document writing during negotiations.