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Using a Pub/Sub Engine as Event Server in a Workflow Management System

IP.com Disclosure Number: IPCOM000015314D
Original Publication Date: 2001-Oct-12
Included in the Prior Art Database: 2003-Jun-20
Document File: 4 page(s) / 149K

Publishing Venue

IBM

Abstract

1. Introduction Workflow management systems [1] support the definition and execution of business processes. The major constructs in drawing processes are activities and control connectors. The activities describe the tasks to be performed, and the control connectors describe the potential sequence in which the activities are to be carried out. Figure 1 (all figures copyrighted IBM/Prentice Hall). shows schematically the structure of such a process graph. Please note that this is for illustration only; workflow management system may use more primitive metamodels for describing business processes (to the extent that they use a simple block structure with implicit control connectors). Figure 1 Process Model Activities are represented as named circles; the name typically describes the purpose of the activity. Activities come in various flavors to address the different tasks that may need to be performed. They may have different activity implementations to meet these diverse needs. Program activities are performed by an assigned program, process activities are performed by another process, and event activities implement the capability to wait for some external action to happen.

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Using a Pub/Sub Engine as Event Server in a Workflow Management System

1. Introduction

    Workflow management systems [1] support the definition and execution of business processes. The major constructs in drawing processes are activities and control connectors. The activities describe the tasks to be performed, and the control connectors describe the potential sequence in which the activities are to be carried out. Figure 1 (all figures copyrighted IBM/Prentice Hall). shows schematically the structure of such a process graph. Please note that this is for illustration only; workflow management system may use more primitive metamodels for describing business processes (to the extent that they use a simple block structure with implicit control connectors).

Figure 1 Process Model

    Activities are represented as named circles; the name typically describes the purpose of the activity. Activities come in various flavors to address the different tasks that may need to be performed. They may have different activity implementations to meet these diverse needs. Program activities are performed by an assigned program, process activities are performed by another process, and event activities implement the capability to wait for some external action to happen.

    Control connectors are represented as arrows; the head of the arrow describes the direction in which the flow of control is moving through the process. The activity where the control connector starts is called the source activity; where it ends is called the target activity.

    Control connectors are represented as arrows; the head of the arrow describes the direction in which the flow of control is moving through the process. The activity where the

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control connector starts is called the source activity; where it ends is called the target activity. When more than one control connector leaves an activity, this indicates potentially parallel work.

Figure 2 illustrates the typical usage of event activies.

Figure 2 Typical Usage of Event Activity

    A first activity Send Invoice sends an invoice to a customer and passes the appropriate customer ID and invoice ID to a second activity, the event activity Await Payment . This event activity waits for the payment to come in. If the event activity expires (wait for too long) or the payment Is not OK, then control goes to the Abort Order activity; if the payment is OK, control goes to the Deliver Goods activity.

    The structure of event activities and their implementation via an event server maintaining two tables, the awaited event table and the posted event table, has been described in [1,3].

    A pub/sub engine provides the capability to have publishers to make information available by sending it to the pub/sub engine. Subscribers can specify to be notified if information is published that matches certain criteria. When published information matches the criteria specified by a subscriber, th...