institut f¨ur informatik - PST Thesis Management Interface - LMU

2.3. Model evolution
• breaking and non-resolvable changes: changes in the metamodel which break the consistency
of the model and cannot be automatically resolved. These changes require
manual intervention by a domain expert.
The concept of non-breaking and breaking changes can also be found in API evolution and
the way it influences programs that make use of the API. An example for a non-breaking
API change is the addition of a method in some class: this change does not break the existing
instances of the class. The renaming of a method is an example for a breaking change: it
breaks the program code that invokes this method by its old name because the code fails to
compile. The code has to be adapted to use the new method name before it can compile
successfully.
The DiffMap model can be used as an information source for adapting AUTOSAR models
to new versions of the AUTOSAR metamodel. This requires a transformation program
that will adapt AUTOSAR models by utilizing metamodel change information found in the
DiffMap model. However, this is not in the scope of GAUTOSAR and will not be further
discussed in this thesis.
OMG M-levels concept (see section 2.1.4) is used to elaborate on frequency and impact
of model change in [Gru06]. M3 models represent modeling tools that are independent
of the problem domain. As such, they are considered unchangeable from the point of view of
the software solution and its life cycle. Changes to M2 models follow from insights into the
problem domain as the software project evolves. These changes may cause inconsistencies
in M1 models. M1 models are changed on a daily basis. Therefore, a need for a catalog of
changes on M2 level and their influence on M1 level is identified. This catalog should be used
to create algorithms for automated break resolution. Such catalogs have been constituted
with varying levels of detail in [CDREP08], [BGGK07] and [HVW11].
Co-adaptation is a term coined in [CDREP08] to describe model adaptation required upon
metamodel change. Furthermore, a transformational approach for model co-adaptation is
proposed where well-defined adaptation steps can be automatically generated from modifications
that the metamodel underwent. In order to facilitate this, a difference model of the
metamodels is exploited to co-adapt the depending models. This difference model consists
of all manipulation operations from the original metamodel to the evolved metamodel. This
method of detecting change is known as recording the metamodel change trace, in contrast
to direct comparison method used in EMF Compare (see section 2.2.4). A discussion of
advantages and disadvantages of both approaches is given in [BGGK07] and [Eys08].
The work in [Eys08] explores the change tracing method in more detail and utilizes wellknown
technologies such as the observer pattern and existing EMF utilities to implement
this method in a patch. A patch is an EMF model that serves as a difference model where
changes are described as atomic primitives, which enables transforming the old metamodel
to the new one and vice-versa. The atomic primitives are then grouped into composite
changes and augmented with information required for the co-adaptation algorithm. The
patch technology was used for the development of the model versioning system in [Kal10]
(see section 2.3.1).
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