OntoUML model V&V tutorial: using OLED tools

Verification and Validation (V&V) are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. Research done at NEMO has amounted to a set of tools called OLED (OntoUML Lightweight Editor). OLED offers a modeling environment that allows V&V and is available at google code. In this post we will focus on OLED but other tool support for OntoUML are available at the NEMO website.

You may download OLED as an executable .jar file and start using it straight away or you can checkout the code using svn and compile it yourself. Having any trouble with the tool please report to the issues page so that the problem may be tracked and fixed, which is more efficient than emailing the developers. Do feel free to approach us with any questions in the comments of this post or via e-mail.

Besides the modeling interface to model using OntoUML's stereotypes, OLED offers a range of tools to Verify, Validate and Transform models. Model transformation is done in an MDD approach which is traditional in NEMO research. The following tools are offered on OLED:

• Transform to Alloy
• Transform to OWL 
• Transform to SVBR
• Transform to text description
• Auto completion of forgotten model elements
• Infer relations
• Model syntax verification
• Anti-Pattern detection
• OCL writing and parsing

The tool support bar. Each icon is explained below

Next we will give a tutorial to contextualize how one may go about using these tools.

1. Click on "New project". This creates a blank diagram to edit.
2. Create a model by clicking on the proper class on the left toolbox ("Elements") and then click on the diagram to place the new class. Relationships are available on the same toolbox as the classes, you have to click on "Relationships" to unveil the relations you may use. Try a model such as the one below. To edit cardinalities, double click the relationship.
   
   
3. This model should show no warningsor errors, but you may delete one of the generalization relations to experiment and generate a warning. You may also test the syntactic verification which will instruct you about the rules you violated.
   OCL writing and checking and the "auto complete" optionare useful for larger models and we will refrain from addressing them now. OCL is used for defining rules and auto-complete is used for correctly transforming fractions of the model.
4. You may also "Detect anti-patterns" , these are based on diagram structure and are the source of errors found in many OntoUML diagrams. Refer to Sales, Barcelos and Guizzardi on "Identification of Semantic Anti-Patterns in Ontology-Driven Conceptual Modeling via Visual Simulation", 2012 for more information on Anti-Patterns. If you test the tool you will see that, even on this very simple example model, an anti-pattern occurs. While this does not mean that the model is wrong, it does call for close investigation as it is a recurring problem.
5. The last tool before we talk about transformations is the Infer Relation tool . This tool generates relationships that can be derived from the language's rules. In the model presented previously, a material relationship between student and school can be derived, as the derivation relationship between the relationship and the enrollment relator is established.
6. Last but not least, there is the Alloy transformation and the OWL, SVBR and text transformations. These are part of the MDD approach carried by NEMO. There are many flavours of OWL transformations, each of which presume one or another design decision. The SVBR and text transformations are aids to understand ("read") the model. While OWL transformations are useful for a number of reasons, the Alloy transformation is particularly useful for model quality as it may be used for validation activities. The transformed Alloy model performs as a simulation of the OntoUML model. By observing the creation, change and destruction of model instances, one may understand what is implied by the model specification and be confronted with the consequences of modelling decisions.