Lars Hamann

Extensive validation of OCL models by integrating SAT solving into USE

The Object Constraint Language (OCL) substantially enriches modeling languages like UML, MOF or EMF with respect to formulating meaningful model properties. In model-centric approaches, an accurately defined model is a requisite for further use. During development of a model, continuous validation of properties and feedback to developers is required, since many design flaws can then be directly discovered and corrected. For this purpose, lightweight validation approaches which allow developers to perform automatic model analysis are particularly helpful. We provide a new method for efficiently searching for model instances. The existence or non-existence of model instances with certain properties allows significant conclusions about model properties. Our approach is based on the translation of UML and OCL concepts into relational logic and its realization with SAT solvers. We explain various use cases of our proposal, for example, completion of partly defined model instances so that particular properties hold in the completed model instances. Our proposal is realized by integrating a model validator as a plugin into the UML and OCL tool USE

Consistency, Independence and Consequences in UML and OCL Models

Properties in UML models are frequently formulated as OCL invariants or OCL pre- and postconditions. The UML-based Specification Environment (USE) supports validation and to a certain degree verification of such properties. USE allows the developer to prove the consistency and independence of invariants by building automatically generated test cases. USE also assists the developer in checking consequences and making deductions from invariants by automatically constructing a set of test cases in form of model scenarios. Suspected deductions are either falsified by a counter test case or are shown to be valid in a fixed finite search space.

Formal specification and testing of model transformations

In this paper we present some of the key issues involved in model transformation specification and testing, discuss and classify some of the existing approaches, and introduce the concept of Tract, a generalization of model transformation contracts. We show how Tracts can be used for model transformation specification and black-box testing, and the kinds of analyses they allow. Some representative examples are used to illustrate this approach.

On integrating structure and behavior modeling with OCL

Precise modeling with UML and OCL traditionally focuses on structural model features like class invariants. OCL also allows the developer to handle behavioral aspects in form of operation pre- and postconditions. However, behavioral UML models like statecharts have rarely been integrated into UML and OCL modeling tools. This paper discusses an approach that combines precise structure and behavior modeling: Class diagrams together with class invariants restrict the model structure and protocol state machines constrain the model behavior. Protocol state machines can take advantage of OCL in form of OCL state invariants and OCL guards and postconditions for state transitions. Protocol state machines can cover complete object lifecycles in contrast to operation pre- and postconditions which only affect single operation calls. The paper reports on the chosen UML language features and their implementation in a UML and OCL validation and verification tool.

Model-driven standardization of public authority data interchange

In the past decade, several electronic data exchange processes between public authorities have been established by the German public administration. In the context of various legacy systems and numerous suppliers of software for public authorities, it is crucial that these interfaces are open and precisely and uniformly defined, in order to foster free competition and interoperability. A community of such projects and specifications for various public administration domains has arisen from an early adopter project in the domain of data interchange between the 5400 German municipal citizen registers. A central coordination office provides a framework for these projects that is put into operation by a unified model-driven method, supported by tools and components, involving UML profiles, model validation, and model-to-text transformations into several technical domains. We report how this model-driven approach has already proven to be effective in a number of projects, and how it could contribute to the development of standardized e-government specifications in various ways. A model-driven method has been successfully applied in e-government standardization.Model validation and model transformation foster time to market and interoperability.The case study reports how the method has been uniformly applied in 8 different projects.

Transformation of UML and OCL Models into Filmstrip Models

This contribution presents an automatic transformation from UML and OCL models into enriched UML and OCL models, so-called filmstrip models, which embody temporal information when employing OCL while maintaining the same functionality as the original model. The approach uses a combination of object and sequence diagrams that allows for a wide range of possible OCL constraints about sequences of operation calls and their temporal properties. The modeler does not need to account for such properties while creating the original model. Errors found by constraints for the filmstrip model can easily be related back to the original model, as the elements of the filmstrip model are synchronized with the original model and the backwards calculation is generally simple. The approach is implemented in a UML and OCL modeling tool.

OCL Tools Report based on the IDE4OCL Feature Model

Previously we have developed the idea of an Integrated Development Environment for OCL (IDE4OCL). Based on the OCL communitys feedback we have also designed and published an IDE4OCL feature model. Here we present a report on selected OCL tools developed by the authors and their teams. Each author gives an overview of their OCL tool, provides a top level architecture, and gives an evaluation of the tool features in a web framework. The framework can also be used by other potential OCL users and tool developers. For users it may serve as an aid to choose a suitable tool for their OCL use scenarios. For tool developers it provides a comparative view for further development of the OCL tools. Our plans are to maintain the collected data and extend this web framework by further OCL tools. Additionally, we would like to encourage sharing of OCL development resources.

OCL-based Runtime Monitoring of JVM hosted Applications

In this paper we present an approach that enables users to monitor and verify the behavior of an application running on a virtual machine at the model level. Concrete implementations of object-oriented software usually contain a lot of tech- nical classes. Thus, the central parts of an application, e.g., the business rules, may be hidden among peripheral functionality like user-interface classes or classes man- aging persistency. Our approach makes use of modern virtual machines and allows the devloper to profile an application in order to achieve an abstract monitoring and verification of central application components. We represent virtual machine bytecode in form of a so-called platform-aligned model (PAM) comprising OCL in- variants and pre- and postconditions. In contrast to related work, our approach uses the original source or bytecode of the monitored application as it stands and does not require any changes. We show a prototype implementation as an extension of the UML and OCL tool USE. Also, we investigate the impact of our approach to the execution time of a monitored system.

OCL-based runtime monitoring of applications with protocol state machines

This paper presents an approach that enables users to monitor and verify the behavior of an application running on a virtual machine (like the Java virtual machine) at an abstract model level. Models for object-oriented implementations are often used as a foundation for formal verification approaches. Our work allows the developer to verify whether a model corresponds to a concrete implementation by validating assumptions about model structure and behavior. In previous work, we focused on (a) the validation of static model properties by monitoring invariants and (b) basic dynamic properties by specifying pre- and postconditions of an operation. In this paper, we extend our work in order to verify and validate advanced dynamic properties, i.,e., properties of sequences of operation calls. This is achieved by integrating support for monitoring UML protocol state machines into our basic validation engine.

On better understanding OCL collections or an OCL ordered set is not an OCL set

Modeling languages like UML or EMF support textual constraints written in OCL. OCL allows the developer to use various collection kinds for objects and values. OCL 1.4 knows sequences, sets, and bags, while OCL 2.0 adds ordered sets. We argue that this addition in the OCL standard was not carried out in a careful way and worsened conceptional problems that were already present previously. We discuss a new way of establishing the connection between the various collection kinds on the basis of explicitly highlighting and characterizing fundamental collection properties.