Extension Files

Extensions files (*.xem) allow you to customize and extend the PowerDesigner metamodel to support your exact modeling needs. You can define additional properties for existing objects or specify entirely new types of objects, modify the PowerDesigner interface (reorganizing and adding property sheet tabs, Toolbox tools and menu items), and define additional generation targets and options.

Extension files have an .xem extension and are located in install_dir/Resource Files/Extende Model Definitions. To view the list of extensions, select Tools > Resources > Extensions > model type. For information about the tools available in resource file lists, see PowerDesigner Resource Files.

Each extension file contains two first-level categories:

Generation - used to develop or complement the default PowerDesigner object generation (for BPM, OOM, and XSM models) or for separate generation. For more information, see Generation Category.
Profile - used for extending the metaclasses in the PowerDesigner metamodel. You can:
- Create or sub-classify new kinds of objects:
  - Metaclasses – drawn from the metamodel as a basis for extension.
  - Stereotypes [for metaclasses and stereotypes only] – sub-classify metaclasses by stereotype.
  - Criteria – sub-classify metaclasses by evaluating conditions.
- Add new properties and collections to objects and display them:
  - Extended attributes – to add metadata.
  - Extended collections and compositions – to enable manual linking between objects.
  - Calculated collections – to automate linking between objects.
  - Dependency matrices – to show dependencies between two types of objects.
  - Forms – to modify property sheets and add custom dialogs.
  - Custom symbols – to change the appearance of objects in diagrams.
- Add constraints and validation rules to objects:
  - Custom checks – to test the validity of your models on demand
  - Event handlers – to perform validation or invoke methods automatically.
- Execute commands on objects:
  - Methods – VBScripts to be invoked by menus or form buttons.
  - Menus [for metaclasses and stereotypes only] – to add commands to PowerDesigner menus.
- Generate objects in new ways:
  - Templates – to extract text from object properties.
  - Generated Files - to assemble templates for preview and generation of files
  - Transformations – to automate changes to objects at generation or on demand.
- Map correspondences between different metamodels:
  - Object generations - to define mappings between different modules in the PowerDesigner metamodel for model-to-model generation.
  - XML imports - to define mappings between an XML schema and a PowerDesigner module to import XML files as models.

Note: Since you can attach several resource files to a model (for example, a target language and one or more extension files) you can create conflicts, where multiple extensions with identical names (for example, two different stereotype definitions) are defined on the same metaclass in separate resource files. In case of such conflicts, the extension file extension usually prevails. When two XEMs are in conflict, priority is given to the one highest in the List of Extensions.

Creating an Extension File
You can create an extension file from the list of extension files or directly embedded in your model.
Attaching Extensions to a Model
Extensions can be in independent *.xem files that are attached to models or can be embedded in model files. Independent extension files can be referenced by multiple models, and any changes made to such a file are shared by all models that attach it. Changes made to extensions embedded in a model file affect only that model.
Exporting an Embedded Extension File for Sharing
If you export an XEM created in a model, it becomes available in the List of Extensions, and can be shared with other models. When you export an XEM, the original remains embedded in the model.
Extension File Properties
All extension files have the same basic category structure.
Example: Adding a New Attribute from a Property Sheet
In this example, we will quickly add a new attribute directly from the property sheet of an object. PowerDesigner will manage the creation of the extension file and creation of all the necessary extensions.
Example: Creating Robustness Diagram Extensions
In this example, we will recreate the Robustness extension file delivered with PowerDesigner to extend the OOM communication diagram to enable robustness analysis. Robustness diagrams sit between use case and sequence diagram analysis, and allow you to bridge the gap between what the system has to do, and how it is actually going to accomplish it.
Metaclasses (Profile)
Metaclasses are defined in the PowerDesigner metamodel and provide the basis for your extensions. You add a metaclass to the Profile category when you want to extend it in some way by modifying its behavior, adding new properties, changing its property sheet or symbol, or even excluding it from your models.
Stereotypes (Profile)
Stereotypes subclassify metaclasses so that extensions are applied to objects only if they bear the stereotype. Stereotypes can be promoted to the status of metaclasses with a specific list, Browser category and custom symbol and Toolbox tool.
Criteria (Profile)
Criteria subclassify metaclasses so that extensions are applied to objects only if they satisfy conditions. You can test an object instance against multiple criteria, and for sub-criteria, its condition and any conditions specified by its parents must be met for its extensions to be applied to the instance.
Extended Attributes (Profile)
Extended attributes define additional metadata to capture for object instances. You can specify a default value, allow users to freely enter numeric, string, or other types of data (or select objects), provide an open or closed list of possible values, or calculate a value.
Extended Collections and Compositions (Profile)
Extended collections define the possibility to associate an object instance with a group of other objects of the specified type. Extended compositions define a parent-child connection between an object instance and a group of sub-objects derived from the ExtendedSubObject metaclass.
Calculated Collections (Profile)
Calculated collections define a read-only connection between an object instance and a group of other objects of the specified type. The collection displays as a sub-tab on the Dependencies tab of the object property sheet. The logic of the collection is defined using VBScript.
Dependency Matrices (Profile)
Dependency matrices allow you to review and create links between any kind of objects. You specify one metaclass for the matrix rows, and the same or another metaclass for the columns. The contents of the cells are then calculated from a collection or link object.
Forms (Profile)
Forms present standard and extended attributes and collections as property sheet tabs or can be used to create dialog boxes launched from menus or property sheet buttons.
Custom Symbols (Profile)
Custom symbols modify the appearance of object symbols in diagrams along with the content displayed on them. You can choose to enforce certain aspects of the symbol format and content, while allowing users some liberty to change others.
Custom Checks (Profile)
Custom checks define additional rules to validate the content of your models. The logic of the check is defined using VBScript. Custom checks appear alongside standard checks in the Check Model dialog.
Event Handlers (Profile)
Event handlers define validation rules or other scripts to run when an event occurs on an object. The logic of the event handler is defined using VBScript. Criteria do not support event handlers.
Methods (Profile)
Methods are written in VBScript and perform actions on objects when they are invoked by other extensions, such as menu items or form buttons.
Menus (Profile)
Menus specify commands to appear in the standard PowerDesigner File, Tools, and Help menus or in contextual menus.
Templates (Profile)
GTL templates extract text from PowerDesigner property values for use in generated files or other contexts.
Generated Files (Profile)
Generated files assemble GTL templates for generation as files or for previewing on the object property sheet Preview tab.
Transformations (Profile)
Transformations define sets of actions to modify objects either before or after a model generation or on request. Transformations are commonly grouped together in transformation profiles.
XML Imports (Profile)
XML imports allow you to define mappings between an XML schema and the PowerDesigner metamodel (and any extensions) to enable the import of XML files complying with the schema. You can specify initialization and post-processing scripts to manage complexities in the import.
Object Generations (Profile)
Object generations allow you to define mappings between one PowerDesigner model type and another based on the two metamodels (and any extensions) to enable the generation of one or more object types.
Global Script (Profile)
The profile contains a global script, which you can use to store functions and variables to be reused in your scripts defined for extensions.