A C++ Framework to Support the Implementation
of the CommonKADS Knowledge Model
Adriano Cosera,, Deucélia Eva Pedrosoa and Roberto Pachecoa, b
a UFSC, Postgraduate Program in Knowledge Engineering and Management, Florianópolis – SC, BRAZIL
b UFSC, Department of Computing and Statistics, Florianópolis – SC, BRAZIL

Introduction
• This work comprises the building of a C++ framework to support
the development of knowledge systems by means of the
CommonKADS methodology.
• The framework consists of a class hierarchy that represents the
CommonKADS knowledge model for a translator.
• This translator in turn generates a C++ code based on the
Conceptual Modelling Language (CML).
• One of the purposes of this study is to show that CommonKADS
methodology is accessible to developers who use commercially
available programming languages like C++.

A Development Process Using the Framework
Final
CommonKADS CML Knowledge CML/C++
C++ Classes
Implementation
Editor Model Translator
Framework
Classes
• This is a possible flow of development for a knowledge system based on
C++, using the framework proposed here.
• A CASE tool (e.g. eKADS) can be used to generate the knowledge model
specification in the CML language.
• This specification is used as input for the automatic C++ code generator.
• The programmer carry out the final composition of the application by
instantiating the generated classes and invoking the necessary methods
to perform the system’s tasks.

A Class Hierarchy for the Knowledge Model
• The classes composing the hierarchy are limited to the knowledge
domain (concepts, relationships, value types and rules types); and to
the knowledge bases, comprised of instances of the rule types.

A Class Hierarchy for the Knowledge Model
• The inference and task layers, which also comprise the knowledge
model, are not considered yet.
• Structures of the knowledge domain are generalized by the
TDomainElement class, thus the rule types can rely on any type of
structure among their antecedent and consequent parameters.
• Each rule type adds connection functions, which are the rules
themselves.
• The knowledge bases are repositories for the rule types and their
connection functions.
• Although the framework does not yet contemplates inferences and tasks,
it is possible to resolve simple problems by means of the
EvaluateBinaryCase method.

The Automatic Translator
• The second component of the framework is an automatic translator that
generates C++ code from the CML language, which is a semi-formal
notation to specify the CommonKADS models.
• The translator has a simple interface that enables the user to open files in
the CML language and generate the C++ classes in a selected folder.
• The files generated are displayed on a list and can be opened and edited
in the same environment.
• The class hierarchy showed is used as the basis for the classes written by
the translator.
• Next figure shows a small knowledge base in CML and part of the
generated C++ code.

The Automatic Translator
CML
KNOWLEDGE-BASE SystemDescription;
USES:
ResidenceAbstraction FROM ResidenceAssessment;
EXPRESSIONS:
applicant.age < 23 has_abstraction applicant.age_category = until22;
applicant.age >= 23 AND
applicant.age < 65 has_abstraction applicant.age_category = bet23_64;
applicant.age >= 65 has_abstraction applicant.age_category = up65;
END KNOWLEDGE-BASE SystemDescription;
C++
void SystemDescriptionConnection1(TRuleType* ruleType)
{ TResidenceAbstraction* rule = dynamic_cast<TResidenceAbstraction*>(ruleType);
TResidenceApplication* antecedent = rule->Antecedent();
TResidenceApplication* consequent = rule->Consequent();
if( antecedent->applicant()->age < 23 )consequent->applicant()->age_category = until22; }
TSystemDescription::TSystemDescription()
{TResidenceAbstraction* ruleType0 = new TResidenceAbstraction();
ruleType0->Connections().push_back(SystemDescriptionConnection1);
Rules().push_back(ruleType0);}

Example of Application
• To validate the framework, it was used to implement an example application
given by Schreiber et al. (1999).
• This example deals with the process of renting real estate in Holland.
People who want to rent a residence must apply with a government agency
that advertises real estate available every fortnight.
• The first task identified in this process is the assessment of the application.
• The knowledge model for the task was extracted from a PROLOG
implementation, reconstructed using the eKADs software and exported in the
CML language.
• The CML specification was then processed by the automatic translator,
which generated the C++ classes.
• To solve the assessment task, little programming effort was necessary.
• Next figure shows the assessment application screen with an application been
evaluated.

Example of Application

Conclusion
• The final objective of the CommonKADS methodology is to build knowledge
systems, into which all the effort made in the analysis and modelling stages
converge.
• It is believed that supporting tools for the implementation of models can
contribute to the consolidation of the methodology on the market.
• We presented a framework conceived to facilitate – and to a certain extent –
automate the implementation of the CommonKADS knowledge model using the
C++ programming language.
• Taking into consideration the limitations of the current stage of the framework, the
results obtained in its application are really satisfactory.
• The programming effort to generate the final implementation of an example
knowledge task was minimal.
• One next step for improving the framework is the modelling and implementation
of the inference and task layers, which also comprise the knowledge model.

References
1. Fowler, M., Scott, K. UML Distilled: A Brief Guide to the Standard
Object Modeling Language. Addison Wesley Longman, Inc., 2000.
2. Motta, E. The Knowledge Modelling Paradigm on Knowledge
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Engineering, 2000.
3. Schreiber, G., Akkermans, H., Anjewierden, A., De Hoog, R., Shadbolt,
N., De Velde, W. V., Wielinga, B. Knowledge Engineering and
Management - The CommonKADS Methodology. The MIT Press, 1999.
4. Schreiber, G., Wielinga, B.J., Akkermans, J.M., Van de Velde, W.,
Anjewierden, A. CML: The CommonKADS Conceptual Modelling
Language. Proc. 8th European Knowledge Acquisition Workshop, 1-25,
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