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The fourth step develops a more complete system.
Prototype 1: Process definition . The first prototype consists of a compo-
nent that is able to read and manipulate process definitions; it represents
the basis for all the following prototypes.
Prototype 2: Process enactment . This prototype is a system that is able to
enact processes based on process definitions; it does not include any user
Prototype 3: User interface . At this stage we develop a web-based user
interface for accessing the functionalities provided by the previous proto-
Prototype 4: Process data . The system is extended with the handling of
workflow relevant data.
Prototype 1: Process definition
This prototype focuses on the modelling of business processes. This proto-
type is able to read a process model from a file and create a corresponding
representation that can be accessed by the upper layer of the final WfMS.
The process description language is based on the standard WPDL and on
The main purpose of this component of the WfMS architecture is to load and
represent the description of a process in an easily accessible manner.
The definitions of the business processes are stored in a file. They are
based on XML; the structure and organization of the description are inspired
by the Workflow Process Definition Language (WPDL) described in WfMC
(1999). This component must be able to load information from an XML file
and provide an easily navigable structure.
The structure of the XML file is based on the description of processes in
the WPDL; we ignore most of the information required by that language. The
description of a process is made up of three main types of elements:
We adapt the core information of WPDL to the XML syntax. The result is
a compact process description language that we name XPDL.
An example of the process that will be used throughout the development
of the WfMS is shown in Figure 21.7.
This process describes in XPDL format the process described in Figure
21.1 by means of an activity diagram. The process is made up of four acti-
vities described by the <ACTIVITY> tags; they are linked by three transitions
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