Workflow Services

The OBE server runtime depends upon a number of workflow services. The services themselves are defined as interfaces and OBE supplies at least one default implementation of each. In some cases, two implementations are supplied: a basic, non-transactional, local in-memory implementation suitable for simple applications and a persistent, transactional, distributed J2EE-based implementation.

Configuration Files

Many of the services initialize themselves from one or more XML and/or Java properties-format configuration files. These files can be located in the $OBE_CONFIG_DIR directory or in the


    META-INF/services

folder inside obeconfig.jar.; entries in the XML files have the general form:

<type id="nmtoken" type="nmtoken"? threadsafe="true|false"?>
    <display-name .../>?
    <author .../>?
    <description .../>?
    <doc-url .../>?
    <!-- Additional service-specific elements -->
    ...
</type>

id: The unique ID of the entry.
type: The ID of the entry which this entry extends.
threadsafe: Indicates whether an instance of the described entry is threadsafe.
display-name: The name to be displayed in design tools.
author: The name of the author or organisation which created the entry.
description: Textual description of the entry.
doc-url: A URL to online documentation for the entry.

The type attribute provides a reuse and extensibility mechanism for user-defined entries. The value must match the ID of one of the other entries in the configuration file. Any properties which are not set explicitly on the child entry will be recursively inherited from the parent type. It is thus possible to set up entire hierarchies of configuration data. N.B. The system does not detect circular dependencies - they will cause infinite loops when the system attempts to resolve an unset property.

The definitive specification of the elements and attributes supported by the XML configuration files is the Castor mapping file


    META-INF/services/castor-map.xml

inside obeconfig.jar.

The Services

Application Event Broker: Provides an interface to external asynchronous event sources including timers.
Assignment Strategy Factory: Provides support for pluggable strategies for assigning work items to workflow participants.
Async Manager: Provides support for asynchronous execution of workflow operations.
Calendar Factory: Provides temporal computation services.
Completion Strategy Factory: Provides support for pluggable activity completion strategies.
Data Converter: Provides data conversion services.
Evaluator Factory: Provides support for evaluation of expressions in arbitrary scripting languages.
Function Factory: Provides support for user-defined functions in expression evaluation.
Instance Repository: Provides storage and lookup for process instances.
Process Repository: Provides storage and lookup for workflow process definitions.
Resource Repository: Provides storage and lookup for arbitrary XML and other documents.
Security Realm: Provides security principal resolution services.
Tool Agent Factory: Provides support for client- and server-side invocation of arbitrary applications and procedures.
Workflow Event Broker: Provides notification services for all workflow lifecycle events.
XPDL Parser Factory: Provides support for parsing and serialization of XPDL documents.