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Chapter 4. The GOPPRR Meta Meta Model – An Extension of GOPRR
∗ \param [ in ] bUseException : o p t i o n a l Boolean f l a g f o r throwing an e x c e p t i o n
∗ in case o f an empty map
∗ \ r e t u r n map o f p o i n t e r s to r o l e s
∗/
: : std : : map< : : std : : s t r i n g , GOPPRR: : CRole∗ >
Roles (GOPPRR: : CObject ∗ const pObject ,
const : : std : : s t r i n g& Type ,
const bool& bSubString = false ,
const bool& bUseException = true
) const throw ( : :GOPPRR: : Error : : CEmpty) ;
All abstraction methods can be found in Section E.1. Details about the deployment and the
implementation are discussed in Chapter 9 along with the openETCS case study code generator
application.
Limitations It is necessary to remark that a concrete GOPPRR C++ abstract syntax model
only holds information about the related model but not about the related meta model. This
means, for example, that for two instances of CObject no information is available if they are
sub- and parent-type, or not. Nevertheless, this is not a major disadvantage because the meta
modelling and the modelling itself should only be related to the modeller, which means here
MetaEdit+.
4.3. GOPPRR XML Schema Definition
To transform an internal MetaEdit+ GOPPRR model 4 , an interface between MetaEdit+ and
the custom generator or rather C++ abstract syntax model has to be established. This is done
by XML as an intermediate model representation. As already introduced in Subsection 3.1.3,
the XML Schema Definition [42, 70] provides a dictionary definition mechanism for XML.
Accordingly, a concrete instance of a XSD can be interpreted as meta model while an XML
valid to the Schema corresponds to a model instance (Figure 3.10).
The fact that XSD provides an object-oriented syntax enables the definition of the XML
Schema in the exact same manner as the GOPPRR C++ abstract syntax model in Figure 4.4.
Furthermore, the usage of so-called key and keyref [42] elements provides the definition of an
even more detailed meta meta model. The C++ abstract syntax model only defines that all
GOPPRR elements are instances / objects in a project object, but in all other associations
among the model those are only connected by references / pointers [79]. An important constraint
is that all GOPPRR elements referenced at any point of the model must occur once as instance
in the related project object. The definition of this constraint in the XSD for GOPPRR renders
the integration into the C++ model unnecessary because it is always instantiated by a XML
model fulfilling it. The complete GOPPRR XSD is located in Section E.2 in the appendix.
4.4. MERL GOPPRR Generator
The generator for transforming GOPRR models in MetaEdit+ to external XML GOPPRR files
is briefly introduced here. Corresponding to the requirement that the GOPPRR C++ abstract
4 GOPPRR model means a concrete instance of a meta model in GOPRR.
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