Ph.D. Thesis - Business Informatics Group

2.3 A DTD to Ecore Transformation Framework
No Explicit Grouping Mechanism
There is no explicit mechanism to group parts of a DTD that semantically belong together
as it is supported in Ecore. Nevertheless, this deficiency can be bypassed by encapsulating
parts of a DTD in separate files and employing parameter entities to import these separated
definitions where appropriate.
Missing Constraint Mechanism
A mechanism for defining complex constraints, as it is supported in Ecore by using the
OCL standard [OMG05d], is not provided for DTDs. Thus, even simple XOR constraints,
which are often required in metamodels, cannot be specified. This deficiency is specifically
problematic, since possible ambiguities in DTDs cannot be resolved and XML documents,
while valid according to their DTD, might still not represent the domain data correctly.
2.3 A DTD to Ecore Transformation Framework
On the basis of the discussion of DTD and Ecore concepts as done in the previous section,
it is now possible to give more insight into the semi-automatic transformation approach,
which is based on previous work [SWK06]. Generally, the transformation approach consists
of an automatic phase and a manual phase (cf. Figure 2.6). The first phase is responsible
for automatically generating a first version of the WebML metamodel and is performed by a
component called MetaModelGenerator (MMG). The metamodel generator employs, in a first
step, a set of transformation rules expressing all identified non-ambiguous correspondences
between DTD concepts and Ecore concepts (cf. Subsection 2.3.1). In a second step of that
phase, a set of heuristics is applied, dealing mainly with the aforementioned deficiencies
by proposing possible correspondences (cf. Subsection 2.3.2). On the basis of these suggestions,
in the second phase, the user needs to manually validate the generated metamodel
and refactor it accordingly (cf. Subsection 2.3.3). The implementation architecture of the
transformation framework is presented in Subsection 2.3.4.
M3
DTD-Grammar Correspondences
conformsTo
implies
conformsTo
MOF
Rules &
Validation &
M2 WebML DTD 1 Heuristics 2 Refactoring WebML Metamodel
Figure 2.6: Two Phase Semi-Automatic Transformation Approach
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