Creating business applications with application descriptors

Application descriptors in earlier TADDM versions were used to help automate the process of discovering, creating, and maintaining business applications. Now, they are an important part of a new mechanism of Business Application Composition. New grouping patterns are cyclically created and the existing grouping patterns are cyclically modified by using data from discovered application descriptors.

Using application descriptors on computer systems and software servers allows for automatic inclusion of these computer systems, servers, along with other components deployed on them and software modules to a specific business application. You can add such system and its components to a business application just by putting an appropriate application descriptor XML file in the predefined location or in the location specified in the collation.properties file. You do not need to use TADDM UI or any configuration. Application descriptor XML files are read during a regular TADDM infrastructure discovery. After this process, the application descriptor agent, together with business application agent, periodically processes all discovered descriptors and generates appropriate selectors, or grouping patterns if necessary, from these discovered descriptors. The generated selectors or grouping patterns are then processed by the business application agent, which generates target business applications.

Selectors are generated together by AppDescriptorAgent and BizAppsAgent. AppDescriptorAgent only creates new grouping patterns from new application descriptors. It is the only task that it executes. It does not refresh selectors based on application descriptors for the existing grouping patterns. BizAppsAgent refreshes such selectors for all business application names that were generated from a specific grouping pattern. To make sure that the grouping patterns contain up-to-date data, when they are created, they are cyclically processed by BizAppsAgent. During the processing of a specific grouping pattern, BizAppsAgent first processes selector types other than the one based on application descriptors. When the agent finishes creating all business applications, it collects their names and refreshes selectors based on application descriptors. For example, the agent creates new selectors, modifies existing selectors or removes a selector if the application descriptor was removed.

To create grouping patterns and selectors based on application descriptors, all application descriptors that are stored in the TADDM database are read and grouped by the name of the target business application. For each business application, a list of components and functional groups that are assigned to them is created by using CIs that are provided in component application descriptors. This list is then divided by the names of functional groups, and selectors specific to each functional group are created. The functional group name is used as a tier name on the generated selector. For more information about tiers configuration, see Tiers configuration.

If the base application descriptor provides the name of the grouping pattern, this grouping pattern is updated with the new list of selectors or a new grouping pattern is created. If the grouping pattern is not provided, the agent checks whether the target business application exists. If it exists, the agent finds the grouping pattern that generated this business application (it can be either grouping pattern for one business application, or more general grouping pattern that generates a group of business applications) and attaches the generated selectors to this grouping pattern. If the target business application does not exist, a new grouping pattern is created to generate just this one business application. If a specific component application descriptor was removed from the target machine and this change was reflected in the TADDM database after the discovery, the BizAppsAgent removes these components from existing selectors. If, after this modification, selector becomes empty, it is also removed. If a grouping pattern no longer contains any selectors, it is disabled and, as a result, removed from processing.

Note: When you define a grouping pattern for many component application descriptors, it must be the same for the base application descriptor and associated component application descriptors. If the associated component application descriptors define various grouping patterns, no pattern is created, even if the base application descriptor does not define any grouping pattern.

You can view the selectors and grouping patterns generated by the application descriptor by using TADDM UI. However, since the selectors of the application descriptor type are generated automatically, you cannot modify or delete them. You can modify only dependency traversal template for them.

In the current release, application descriptors are stored in a new class named BizAppDescriptor. During migration, all existing application descriptors are transformed to this new class. Grouping patterns that are generated during migration use these migrated application descriptors.

You can use the following strategies for creating and deploying application descriptors:

Define application during development and deployment. By doing so, you can capture the most accurate and complete information about the packaging of modules in business applications.
After the application is already in place (by creating the descriptors and putting them in the appropriate location on the target computer systems), you can deploy application descriptors.