Database Reference
In-Depth Information
Since the UML is the standard modeling language of the Object Management Group
1
,
Harel's statecharts will soon become common. Second, statecharts are easy to understand
and they do not have the problem of exponential growth of states that plague ordinary state
transition diagrams (Harel, 1988). We shall elaborate on this point in the Related Work sec-
tion. Third, their semantics are rigorous enough for formal analysis on various aspects of
structured business workfl ows (Harel & Naamad, 1996).
Within the framework of statecharts, we will show how to model workfl ow concepts
and present algorithms that determine whether a given business workfl ow has certain
predefi ned properties. We will then use a case study with Moore BCS (recently recast as
Moore Wallace Incorporated) to explore the characteristics of a business workfl ow. The
algorithms we develop in this study will become part of a software design tool that we will
develop in the future.
RELATED WORK
An overview of workfl ow management using the latest technology can be found in
Georgakopoulos, Hornick, and Sheth (1995). Specifi cation and implementation of excep-
tions in workfl ow management systems are discussed in Casati, Ceri, Paraboschi, and Pozzi
(1999) and workfl ow evolution in Casati, Ceri, Pernici, and Pozzi (1998).
Active database systems have been studied extensively (Paton & Diaz, 1999). Active
database systems and workfl ow management systems are related since both types of systems
employ triggers to respond to external and internal events and exceptions. We are interested
in three important properties of active database systems in this research, namely termination,
confl uence, and observable determinism, which are formally defi ned in Allen, Hellerstein,
and Widom (1995). More discussion on active database systems, which includes several
research prototypes and commercial products, can be found in Zaniolo (1997).
The statemate approach, which uses statecharts in modeling reactive systems, is de-
scribed in Harel and Politi (1998) and its semantics in Harel and Naamad (1996). By far,
the statemate semantics of statecharts is the most rigorous and precise execution semantics
defi ned for statecharts and it has been in use for more than ten years (Harel & Naamad,
1996). Here we point out the most signifi cant aspects of the execution semantics. The reader
may consult Harel and Politi (1998) and Harel and Naamad (1996) for details.
The behavior of a system described in statemate semantics is a set of possible runs,
each representing the responses of the system to a sequence of external stimuli generated by
its environment
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. A run consists of a series of detailed snapshots of the system's situation;
such a snapshot is called a status. The fi rst in the sequence is the initial status, and each
subsequent one is obtained from its predecessor by executing a step (see Figure 1).
Figure 1: Status and step
