Pattern 15 (Task to Environment - Push)

FLASH animation of Data Interaction - Task to Environment - Push-Oriented pattern

Description

The ability of a task to initiate the passing of data elements to a resource or service in the operating environment.

Example

The Calculate Mileage task passes the mileage data to the Corporate Logbook database for permanent recording.

Motivation

The passing of data from a task to an external resource is most likely to be initiated by the task itself during its execution. Depending on the specific requirements of the data passing interaction, it may connect to an existing API or service interface in the operating environment or it may actually invoke the application or service to which it is forwarding the data.

Overview

Figure 14 illustrates the various data passing scenarios between tasks and the operating environment.

Figure 14: Data interaction between workflow tasks and the operating environment

There are a wide range of ways in which this pattern can be achieved, however these tend to divide into two categories:

In both cases, the data passing activity is initiated by the task and occurs synchronously with task execution. Although, it is typically task-level data elements that are trafficked, any data items that are accessible to the task (i.e. parameters, scope block, case, folder and global data) may be transferred.

Context

There are no specific context conditions associated with this pattern.

Implementation

Staffware provides the Automatic Step construct for passing data elements from task instances to external programs. FLOWer enables data to be passed to external applications using the Operation Action construct and to external databases using Mapping Objects. COSA provides a broad number of Tool Agents which facilitate the passing of data to external applications and databases. Similarly iPlanet provides a range of XML and HTTP-based mechanisms that can be incorporated in task implementations for passing data to external applications. Websphere MQ is more limited in its support and delegates the passing of data elements to user-defined program implementations. BPMN supports the pattern via a Message Flow from a Task to the boundary of a Pool representing the environment. XPDL and BPEL are limited to passing data elements to web services.

Issues

One difficulty that can arise when sending data to an external application is knowing whether it was successfully delivered. This is particularly a problem when the external application does not provide immediate feedback on delivery status.

Solutions

The most general solution to this problem is for a subsequent task in the case to request an update on the status of the delivery using a construct which conforms to the Data Interaction - Environment to Task - Pull Oriented pattern (WDP-16) and requires an answer to be provided by the external application. Alternatively, the external application can lodge a notification of the delivery using some form of Event-based Task Trigger (i.e pattern WDP 38) or by passing data back to the process (e.g. using the Data Interaction - Environment to Task - Push-Oriented pattern (WDP-17) ). This is analogous to the messaging notion of asynchronous callback.

Evaluation Criteria

An offering achieves full support if it has a construct that satisfies the description for the pattern. It achieves a partial support rating if programmatic extensions are required to facilitate the data passing.

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