Extending a UML and OCL Tool for Multi-Levels:
  Applications towards Model Quality Assessment
                                   Khanh-Hoang Doan                                              Martin Gogolla
                         Department of Computer Science                               Department of Computer Science
                               University of Bremen                                         University of Bremen
                           D-28334 Bremen, Germany                                      D-28334 Bremen, Germany
                         doankh@informatik.uni-bremen.de                              gogolla@informatik.uni-bremen.de



   Abstract—Currently, meta- and multi-level modelling is gain-                   III. A PPLICATION : M ODEL Q UALITY A SSESSMENT
ing more and more attention. A natural, upcoming question is,
how to extend existing two-level approaches to cover multi-levels.
                                                                                 Model quality assessment helps modelers to detect errors or
In this contribution, we extend the UML and OCL tool USE in                   mistakes on their models. These assessment properties might
order to describe multi-level models. We also apply the extension             include design properties, respecting naming conventions or
to demonstrate the usefulness of multi-level modelling for model              metrics properties [2]. We introduce a proposal that employs
querying and model quality assessment.                                        OCL utilizing the three-level modeling approach as presented
                                                                              before. Thus, we can automatically evaluate quality properties
                                I. I NTRODUCTION
                                                                              of a user model. Fig. 2 shows the workflow of our proposal
   In this contribution we show how to upgrade a two-                         for model quality evaluation, which uses reflective OCL con-
level modeling tool to three levels of modeling by adding                     straints as a major ingredient.
the OMG (Object Management Group) UML meta-model
to the topmost level. In addition to this tool extension, we
discuss reflective model querying as it plays an essential
role. Therefore, we also present a reflective model querying
approach using OCL for the meta-model. We apply meta-
model queries for model quality evaluation. Developers can
use an appropriate method to evaluate their model and find
drawbacks and problems on it.

              II. M ETA - MODELING IN T OOL USE
   In the current contribution, we introduce an approach, in
which the MOF architecture is integrated into USE for multi-
level modelling. Roughly speaking, we now make the third
OMG layer M2 explictily available, and an instance of the
M2-model corresponding to the user model is added to the                               Fig. 2. Worflow of model quality assessment process.
M1-layer. Fig. 1 shows the general schema for the three-level
modeling in the new version of USE.                                                                    IV. C ONCLUSION
                                                                                 This contribution has proposed an extension of the tool USE
         M2       UML Meta model                                              that supports three-level modelling where the middle level
                                                                              can be seen at the same time as an object diagram, i.e., the
               <<instanceOf>>
                                                                              instantiation of the meta model, and as a class diagram, i.e.,
                                       <<viewOf>>
                                                                              the type model for the lower level. Based on these ideas, we
         M1          Meta model                                               present approaches for model quality assessment.
                                                     UML User model
                      instances

                                       <<viewOf>>                                                         R EFERENCES
                                                             <<instanceOf>>
                                                                              [1] Gogolla, M., Büttner, F., Richters, M.: USE: A UML-based Specification
                                                                                  Environment for Validating UML and OCL. Sci. Comput. Program.
         M0                                         Run-time instances            69(1-3), 27–34 (2007)
                                                                              [2] López-Fernández, J.J., Guerra, E., de Lara, J.: Assessing the Quality
                                                                                  of Meta Models. In: Proc. 11th Workshop MoDeVVa@MODELS 2014.
          Fig. 1. General schema for the three-level modeling.                    pp. 3–12 (2014)