A ModelLayer model lets you inspect the structural content of an MDriven model—such as classes, attributes, associations, and state machines—and is for developers creating model-aware tools, exports, or plugins.

What ModelLayer contains

ModelLayer is a meta-model: its instances describe another model rather than the business data handled by that model. For example, when your application model contains a Customer class with a Name attribute, ModelLayer contains metadata representing that class and attribute.

ModelLayer holds knowledge about:

• Classes
• Attributes
• Associations
• State machines

Use ModelLayer when you need the core structural definition of a model.

ModelLayer and ExtendedModelLayer

A model can also contain design-time information beyond its structural definition. This information is represented by ExtendedModelLayer, which extends ModelLayer.

Meta-model	Contains	Example use
ModelLayer	Core model structure: classes, attributes, associations, and state machines.	Find every class with more than three attributes.
ExtendedModelLayer	ModelLayer content plus diagrams, ViewModels, report definitions, enterprise architecture information, and other extended design information.	List all ViewModels or inspect diagrams and tagged values.

For example, an expression that queries classes and their attributes is evaluated against the meta-model:

Class.allinstances->select(c|c.Feature->filterontype(Attribute)->size>3)

This expression returns classes that have more than three attribute features.

Use ModelLayer in a plugin

Use MDriven Designer to work with plugins. Open the plugin meta-model from File > Plugins > Open New Meta-model for Plugins. This opens the extended MDriven meta-model, allowing your plugin model to define ViewModels that query the model currently open in MDriven Designer.

For example, you can define a ViewModel that lists ViewModels by name:

Span.allinstances->orderby(name)

The ViewModel executes against the ExtendedModelLayer instance that represents the user's current model. This lets you present information such as all constraints, all classes, or elements with a specified tagged value.

Export model information

You can also export model information for documentation and analysis. A MIF (Model Information File) export includes ViewModels, actions, classes and their content, and state machines in a ModelMeta model. The export also analyzes expressions and records what each expression uses, which provides cross-reference information.

For example, a ModelMeta viewer can show a ViewModel, its rendered view, and the model elements it uses. You can follow an attribute or association end to see where it is used elsewhere in the model.

See also

• Documentation:Model
• Documentation:MDriven Designer and Modlr extensions–exporting data
• Training:The ViewModel
• Documentation:ViewModel for Business