Designing active objects in DEGAS

This report discusses application design for active databases, in particular for the active object-based database programming language DEGAS. In DEGAS one modularisation principle, the object, is applied to all elements of the application, including rules. We discuss a design process consisting of four phases, corresponding with the four kinds of capabilities in a DEGAS object, attributes, methods, rules, lifecycles. The elements of this design process are similar to those found in a design methodology such as OMT. To illustrate the design process we use the example of workflow management. In addition, it shows that the application of one modularisation to all elements of an active database leads to a clear modularisation of the workflow application, Furthermore, this modularisation facilitates all important workflow evolutions

Time Issues in Advanced Workflow Management Applications of Active Databases

Workflow management systems schedule tasks in accordance with previously known process types. Additionally, advanced workflow applications have to deal with parametric processes and exceptional situations. Using active database technology to implement such applications results in mature demands for their respective time handling capabilities. This regards both, the possibilities of time specification as well as a sophisticated time management within the rule execution mechanism. In this paper we examine necessary time handling potentials for active databases in order to implement advanced workflow. To do so, the ontologies of advanced workflow and corresponding time structures are introduced. We will tackle the problems that occur when implementing advanced workflow, especially predictive and reactive scheduling, synchronisation and recovery in the active database settings. It will turn out that techniques fulfilling soft real--time requirements are sufficient