Jens Brüning

Getting SW Engineers on Board: Task Modelling with Activity Diagrams

This paper argues for a transfer of knowledge and experience gained in task-based design to Software Engineering. A transformation of task models into activity diagrams as part of UML is proposed. By using familiar notations, software engineers might be encouraged to accept task modelling and to pay more attention to users and their tasks. Generally, different presentations of a model can help to increase its acceptance by various stakeholders. The presented approach allows both the visualization of task models as activity diagrams as well as task modelling with activity diagrams. Corresponding tool support is presented which includes the animation of task models. The tool itself was developed in a model-based way.

Modeling and Formally Checking Workflow Properties Using UML and OCL

In this paper, a new metamodel for workflows is described by using UML. The underlying UML class diagram is formally extended with OCL pre- and postconditions for operations and OCL invariants for system states. The metamodel allows the developer to specify processes, activities in processes and temporal relations between them. Known workflow patterns are formally captured in the metamodel and sophisticated temporal relations between activities can be expressed easily. Development of workflow models is explained as well as process instantiation and process execution on the basis of a tool realizing parts of the UML action semantics. Prototypical process execution and animation allows the designer to discover properties of the designed processes and activities in early phases of the development without the need for building a full implementation.

TTMS: A Task Tree Based Workflow Management System

In this paper, an approach to use task trees in a workflow management system (WfMS) is presented. As hierarchical models task trees capture several hierarchy levels of a workflow in one model. A workflow editor visualizes the models also as flowcharts similar to UML activity diagrams. The WfMS use these models as input and instantiates and executes them. The system is web-based and can be easily accessed by users with any browser clients. This paper motivates the approach to use task trees that produce hierarchical and structured workflow specifications. The proposed language might help end-users to better understand workflow models with its problem oriented hierarchical modeling character. Temporal operators from the task models are compared with certain operators from established workflow languages. In addition, in TTMS an instantiation time concept is implemented, where decision operators are evaluated at the very moment the process is instantiated. Consequently the task tree modeling language is enhanced for modeling decisions in the context of workflow management.

Evaluating and debugging OCL expressions in UML models

This paper discusses the relationship between tests and proofs with focus on a tool for UML and OCL models. Tests are thought of as UML object diagrams and theorems or properties which are to be checked are represented as OCL constraints, i.e., class invariants or operation pre- and postconditions. The paper shows for the UML and OCL tool USE (UML-based Specification Environment) how to trace and debug the validity of an expected theorem (an OCL constraint) within a given test case (a state model in the form of a UML object diagram).

Making task modeling suitable for stakeholder-driven workflow specifications

This paper discusses approaches for specifying workflows based on task models. These task models represent activities of stakeholders in different ways. It is shown how the development process of workflow specifications can be supported to get hierarchical, structured and sound specifications. Further on, a language CTML is introduced that was developed to specify activities in smart environment. The language has the potential to be used to specify general workflow specifications as well. It is demonstrated how cooperative work can be specified using this language.

UML Metamodel-based Workflow Modeling and Execution

In this paper, we present a UML metamodel-based approach for creating and executing workflow models. The workflow modeling language is introduced through its abstract syntax, and an evaluation shows how this language supports known workflow patterns. Some patterns can be expressed easier compared to established languages like EPCs or BPMN. Organizational and data aspects in workflow models can be described on the basis of the presented metamodel. The workflow models can be instantiated and executed with a tool realizing parts of the UML action semantics. At an early stage of design, our workflow models can be evaluated by testing scenarios with the used tool in combination with the developed workflow plug in. Employing the tool, dynamic aspects of the workflow process models together with data and organizational aspects can be evaluated. During execution of the workflow scenarios, the workflow models can be adaptively changed, and data can be captured and evaluated by formulating process mining queries with UMLs OCL (Object Constraint Language).

Extending ASSL: Making UML Metamodel-based Workflows executable

ASSL is a language that enables UML developers to test and certify UML and OCL models (5). Snapshots of system states are semi-automatically created and main parts of the UML action semantics is implemented by the language. Its interpreter is the well-known UML modeling tool USE. The article proposes a number of language extensions to ASSL. These include (sub-) procedure calls and pre- and postcondition checks on entering and exiting of operations using OCL. The paper motivates the need for these extensions as well as their usage and development along the problem of metamodel-based execution of workflow models. Executable workflow models, driven by ASSL procedures, are introduced in detail to present the usage of ASSL and our extensions.

Declarative Models for Business Processes and UI Generation using OCL

This paper presents an approach to model business processes and associated user interfaces in a declarative way, relying on constraints. An UML-based meta-model to define processes, activities and user-interface objects is proposed. Connecting activities and user interface objects in an integrated model allows expressing interdependencies and mutual effects. Flexible execution logic for workflows and UI control flows are specified by OCL invariants. The model is constructed for the UML tool USE. Using object snapshots, USE can animate and validate business scenarios. Snapshots represent states of a process and a UI at specific times. Such animation enables business process and UI designers to discuss sensible scenarios on basis of the flexible declarative models. The intention is to create validated concrete process models in connection with UI elements that will provide a basis for the system implementation.

On the Suitability of Activity Diagrams and ConcurTaskTrees for Complex Event Modeling

In this paper, we analyze and extend modeling possibilities for complex events in the semiformal business process modeling languages UML activity diagrams and ConcurTaskTrees (CTT). The goal of this paper is to provide an intuitive abstract starting point for complex event specifications in a model-based approach. The resulting models should increase the understandability of the models themselves and the discussion taking place with the developers and the stakeholders. A hierarchy concept for advanced visual event modeling is introduced to activity diagrams. In these models time, data and cardinality aspects can be expressed. A different approach for complex event modeling is proposed using hierarchical task models with CTT. We transform given temporal operators from CTT that are based on process algebra to event algebra. Some extensions for CTT-operators are used to express specific complex event models in a semiformal way.