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Chapter 4. The GOPPRR Meta Meta Model – An Extension of GOPRR
usable for C++ classes and objects. The resulting structure of the GOPPRR C++ abstract
syntax model is shown in Figure 4.4. Compared with the original abstract syntax, the following
main extensions and modifications were done:
• An additional class CCall 2 was added, which is used by CConnection as aggregation [64] to
combine an object (CObject), a role (CRole), and an optional port (CPort). Without this
addition, it could not be distinguished, which objects and ports belong to the same call.
Caused by the circumstance that ports are optional, the size of direct associations [64] of
ports in CConnection could be different and the assignment of ports to a concrete pair of
object and role would be non-unique. CCall should be interpreted as the definition of
one concrete end of a connection (CConnection) or rather binding (CBinding).
• The class CGraphicalContainer was added to provide the information of graphical
containment of objects and relationships. Instances are related to exact one graph object
because the graphical containment feature is only valid in a certain graph but not for a
whole project.
• For all associations that ends at classes representing GOPPRR base elements and have
in their multiplicity [64] a not limited upper bound (stated by a *) a STL map [79] is
used as container. The object identifier 3 (OID) is used as key [79] value in the map. The
map ensures that no duplicates exist in association and elements can be easily accessed
by their OID, but it also can be iterated, like a vector / stack or a list.
While the C++ GOPPRR abstract syntax model provides access to all model information,
it makes the processing of bindings in a certain graph quite more complex. Compared to
the concrete syntax model used for MERL, bindings now cannot easily navigated by directly
stating the type name, like
. o b j e c t 1 ~role1 >r e l a t i o n s h i p ~ r o l e 2 . o b j e c t 2
or
. o b j e c t 1#port1~role1 >r e l a t i o n s h i p ~ r o l e 2#port2 . o b j e c t 2
To reduce this drawback, the graph representation class CGraph provides several methods that
abstracts the navigation via bindings. In the example below, the method returns all roles of a
certain type connected to a certain object. The returned map of roles can be then processed or
used for further navigation to relationships or roles.
/∗ !
∗ \ b r i e f a b s t r a c t i o n method
∗
∗ Gets c e r t a i n r o l e s connected to a c e r t a i n o b j e c t in a c e r t a i n graph .
∗
∗ \param [ in ] pObject : p o i n t e r to t h e o b j e c t
∗ \param [ in ] Type : r o l e t y p e
∗ \param [ in ] b SubString : i f true , Type only must be a s u b s t r i n g o f r o l e t y p e
2 The name was chosen according to the connectionCall composition in the original structure.
3 OIDs are not part of the original GOPRR meta meta model but are created in MetaEdit+ for each instance
of a GOPRR element and are unique within a project.
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