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Property sharing

6.3 Model integration and reuse

One of the most powerful features of MetaEdit+ is that you can integrate metamodels and design information based on them. Basically, the integration features allow you to link and reuse data across different languages, maintaining a flow of information between different languages.

By linking we mean that you can link object elements to other graphs. Linking of objects to graphs is accomplished by using either decomposition structures or explosion. An example of decomposition can be found from the Watch example in which a state in a WatchApplication model can be decomposed into a subdiagram. Also, most of the class diagrams found in MetaEdit+ support decomposition of objects and their relationships into new graphs.

Another important feature is reuse. You can reuse either:
*whole objects, or
*properties.
Reuse of an object means that you can use the same design information stored in the object in other graphs, even if they are in different projects. In line with the principles of reuse, if you change the specifications of the reused object in one graph, it automatically updates changes to other graphs even if they were originally made with a different modeling language.

To test reuse of objects:
1)Open a graph with any tool (i.e. Diagram Editor, Matrix Editor, Table Editor)
2)Select the Add Existing... command.
3)Select any object from the dialog that opens.

Reuse of properties allows a more detailed reuse option: you do not need to reuse whole objects but you can instead just reuse some of the object’s properties. For example, a message name in an object diagram can be shared as the method name of another object.

To try out reuse of properties:
1)Open a dialog for any existing object or relationship in any tool.
2)Move the cursor to the field to be reused (text field).
3)Open a pop-up menu by pressing the right mouse button and select Share Property....
4)Select any text specification to be shared from the dialog that appears.

After property sharing the object refers to the shared property and therefore any changes to the property will affect that property in every place where it is used.

Property sharing

A particular property can be shared between two or more non-properties, meaning that changes to the property via one non-property are also reflected in the other non-properties. Therefore the property is basically defined only once and several properties refer to the same value. For this to be possible, the property in each of them which is to be common must have the same property type, and the data type of that property type must be string, number, or text.

This can be used in e.g. class diagrams, so that a ‘Superclass’ string property in one class can be shared with the ‘Class name’ string property in the superclass. Thus if the ‘Class name’ of the superclass is changed, this will also be reflected in the ‘superclass’ property of the subclass. (Another, better way of achieving the same result would be to have Superclass property with a Non-property data type of Class: that way the whole superclass can be linked, not just its name).

The property sharing can be accessed through property dialogs by clicking the property field and selecting Share Property... from the pop-up menu (see Section 3.3.1 to see how property sharing can be accessed). Note that if you change the property value in one place all other non-properties that have that property will show the changed value as well.

To remove property sharing, select the shared field and choose Remove Sharing from the pop-up menu. Therefore, by making both commands one after another you can copy property values from other non-properties, and remove the sharing so changes to one no longer affect the other.

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