Developing a DSL Graphical Notation - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 71

source reference and the Target Feature to the target feature. Also ensure
that the proper Tool and Diagram Link are selected. Upon Finish , browse the
mapping model in the editor. Check each property to verify that all are correct,
and use the Validate action from the context menu.
Regarding our two types of links, notice that they illustrate the two most
common methods of providing link mappings for a diagram. The subtopics ref-
erence maps to a link that shows the relationship between Topic elements. In
this case, we need to indicate only the Target Feature in our link mapping,
leaving the other properties blank. The relationship link shows how to map a
link to a domain model class—in this case, our Relationship class. To com-
plete the mapping definition, we need to specify the Element and its Contain-
ment Feature , Source Feature , and Target Feature for the link.
Let's go through the mapping model in some detail, because it often causes
confusion. Beginning with the Canvas Mapping element, you can see that the
Map domain Element will be represented by the mindmap Diagram Canvas
from our mindmap.gmfgraph model. Similarly, the diagram canvas will have a
Palette , represented by our mindmap.gmftool model's mindmapPalette
element. Note that the Menu and Toolbar Contributions properties are
blank because GMF has not yet implemented them, as seen in Table 4-1.

Table 4-1 Mindmap Canvas Mapping

Element Property Value

Mapping

Canvas Domain Model Mindmap

Element Map

Palette Palette mindmapPalette

Diagram Canvas Canvas mindmap

For our Topic node, we see in the properties of the Top Node Reference
that new instances of Topic elements are to be maintained in the elements con-
tainment reference of our Map class, as shown in Table 4-2. The Children
Feature property is left blank because we retrieve and store our Topic
elements directly from the elements containment feature.