Pattern 39 (Chained Execution)

FLASH animation of Chained Execution pattern

Description

The ability to automatically start the next work item in a case once the previous one has completed. The transition to Chained Execution mode is at the instigation of the resource.

Example

Immediately commence the next work item in the Emergency Rescue Coordination process when the preceding one has completed.

Motivation

The rationale for this pattern is that case throughput is expedited when a resource is allocated sequential work items within a case and when a work item is completed, its successor is immediately initiated. This has the effect of keeping the resource constantly progressing a given case.

Overview

Chained Execution involves a resource undertaking work items in the same case in "chained mode" such that the completion of one work item immediately triggers its successor which is immediately placed in the resource's work list with a started status. This pattern is illustrated by the transition R:chained_execution in Figure 7. It is important to note that this transition is represented by a dashed line because it jumps from one work item to another, i.e., it links the life-cycles of two different work items.

Context

There are no specific context conditions associated with this pattern.

Implementation

In order to implement this pattern effectively, the majority (if not all) of the work items for a given case need to be allocated to the same resource and it must execute them in a strict sequential order. This approach to work distribution is best addressed by a case handling system and not surprisingly FLOWer offers direct support for it. The manner in which work items are initiated in BPMN and UML 2.0 ADs (i.e. as soon as the required number of initiating tokens are received) implies that this pattern is the default behaviour exhibited during process execution.

Issues

Chained Execution offers a means of achieving rapid throughput for a given case however in order to ensure that this does not result in an arbitrary delay of other cases, it is important that cases are distributed across the widest possible range of resources and that the distribution only occurs when a resource is ready to undertake a new case.

Solutions

This issue is managed in FLOWer by defining Work Profiles that distribute cases appropriately and ensuring that resources only request new case allocation when they are ready to commence the associated work items.

Evaluation Criteria

An offering achieves full support if it satisfies the description for the pattern.

Product Evaluation

To achieve a + rating (direct support) or a +/- rating (partial support) the product should satisfy the corresponding evaluation criterion of the pattern. Otherwise a - rating (no support) is assigned.

Summary of Evaluation