The next talk in our seminar was about DiaMeta, the successor of the diagram editor generator DiaGen. In contrast to DiaGen DiaMeta is based on a metamodel instead of a hypergraph grammar. Not that metamodels are more powerful: this truly is not the case. But people are so familiar with drawing class diagrams aka metamodels that nowadays metamodel-based tools are more popular.
DiaMeta is based on the Eclipse Modeling Framework we already have discussed (there also is an experimental version based on MOF, see references below). This is very benefitial from an application integration point of view, because the abstract syntax of diagrams can be serialized in standard compliant XMI.
The most interesting point to know about syntax analysis is that it is basically performed by solving a constraint satisfaction problem. This important correlation has been noticed by Minas 2006. Therefore DiaMeta has to make heavy use of the powerful reflective features EMF provides.
The picture shows the overall DiaMeta architecture. There are two important differences to DiaGen. The first one is that the reducer does not create a reduced hypergraph model any more, but instead a so-called instance graph. This is a graph whose nodes are marked with class names of the metamodel and whose edges represent references. However, these annotations do not have to be the concrete object types (they even can be names of abstract classes). It is the task of the so-called checker, the second important difference!, to map these nodes to non-abstract classes and instantiate corresponding objects. The instance graph is therefore used as a constraint net that can be solved using the information given in the metamodel, e.g. references, inheritance relationships, cardinalities, etc. This is described in detail in the first paper mentioned in Further reading.
Further reading:
- Generating meta-model-based freehand editors. Minas, Proc. of 3rd International Workshop on Graph Based Tools (GraBaTs'06), 2006.
- Syntax analysis for diagram editors: A constraint satisfaction problem. Minas, In Proc. of the Working Conference on Advanced Visual Interfaces (AVI'2006), 2006.
- Generating visual editors based on Fujaba/MOFLON and DiaMeta. Minas, Proc. Fujaba Days 2006
- DiaMeta website
