Jana Koehler

The Refined Process Structure Tree

We consider workflow graphs as a model for the control flow of a business process model and study the problem of workflow graph parsing, i.e., finding the structure of a workflow graph. More precisely, we want to find a decomposition of a workflow graph into a hierarchy of sub-workflows that are subgraphs with a single entry and a single exit of control. Such a decomposition is the crucial step, for example, to translate a process modeled in a graph-based language such as BPMN into a process modeled in a block-based language such as BPEL. For this and other applications, it is desirable that the decomposition be unique, modularand as fine as possible, where modularmeans that a local change of the workflow graph can only cause a local change of the decomposition. In this paper, we provide a decomposition that is unique, modular and finer than in previous work. It is based on and extends similar work for sequential programs by Tarjan and Valdes [11]. We show that our decomposition can be computed in linear time based on an algorithm by Hopcroft and Tarjan [3] that finds the triconnected components of a biconnected graph.

Managing architectural decision models with dependency relations, integrity constraints, and production rules

Software architects consider capturing and sharing architectural decisions increasingly important; many tacit dependencies exist in this architectural knowledge. Architectural decision modeling makes these dependencies explicit and serves as a foundation for knowledge management tools. In practice, however, text templates and informal rich pictures rather than models are used to capture the knowledge; a formal definition of model entities and their relations is missing in the current state of the art. In this paper, we propose such a formal definition of architectural decision models as directed acyclic graphs with several types of nodes and edges. In our models, architectural decision topic groups, issues, alternatives, and outcomes form trees of nodes connected by edges expressing containment and refinement, decomposition, and triggers dependencies, as well as logical relations such as (in)compatibility of alternatives. The formalization can be used to verify integrity constraints and to organize the decision making process; production rules and dependency patterns can be defined. A reusable architectural decision model supporting service-oriented architecture design demonstrates how we use these concepts. We also present tool support and give a quantitative evaluation.

Instantaneous Soundness Checking of Industrial Business Process Models

We report on a case study on control-flow analysis of business process models. We checked 735 industrial business process models from financial services, telecommunications and other domains. We investigated these models for soundness (absence of deadlock and lack of synchronization) using three different approaches: the business process verification tool Woflan, the Petri net model checker LoLA, and a recently developed technique based on SESE decomposition. We evaluate the various techniques used by these approaches in terms of their ability of accelerating the check. Our results show that industrial business process models can be checked in a few milliseconds, which enables tight integration of modeling with control-flow analysis. We also briefly compare the diagnostic information delivered by the different approaches.

Analysis on demand: Instantaneous soundness checking of industrial business process models

We report on a case study on control-flow analysis of business process models. We checked 735 industrial business process models from financial services, telecommunications, and other domains. We investigated these models for soundness (absence of deadlock and lack of synchronization) using three different approaches: the business process verification tool Woflan, the Petri net model checker LoLA, and a recently developed technique based on SESE decomposition. We evaluate the various techniques used by these approaches in terms of their ability of accelerating the check. Our results show that industrial business process models can be checked in a few milliseconds, which enables tight integration of modeling with control-flow analysis. We also briefly compare the diagnostic information delivered by the different approaches and report some first insights from industrial applications.

Applying Patterns during Business Process Modeling

Although the business process community has put a major emphasis on patterns, notably the famous workflow patterns, only limited support for using patterns in todays business process modeling tools can be found. While the basic workflow patterns for control flow are available in almost every business process modeling tool, there is no support for the user in correctly applying these simple patterns leading to many incorrectly modeled business processes. Only limited support for pattern compounds can be found in some tools, there is no active support for selecting patterns that are applicable in some user-determined context, tools do not give feedback to the user if applying a pattern can lead to a modeling error, nor do they trace the sequence of applied patterns during the editing process. In this paper, we describe an extension of a business process modeling tool with patterns to provide these capabilities. We distinguish three scenarios of pattern application and discuss a set of pattern compounds that are based on the basic workflow patterns for control flow. We present an approach where business users receive help in understanding the context and consequences of applying a pattern.

The Role of Visual Modeling and Model Transformations in Business-driven Development

This paper explores the emerging paradigm of business-driven development, which presupposes a methodology for developing IT solutions that directly satisfy business requirements and needs. At the core of business-driven development are business processes, which are usually modeled by combining graphical and textual notations. During the business-driven development process, business-process models are taken down to the IT level, where they describe the so-called choreography of services in a Service-Oriented Architecture. The derivation of a service choreography based on a business-process model is simple and straightforward for toy examples only-for realistic applications, many challenges at the methodological and technical level have to be solved. This paper explores these challenges and describes selected solutions that have been developed by the research team of the IBM Zurich Research Laboratory.

From business process model to consistent implementation: a case for formal verification methods

Todays business applications and their underlying process models are becoming more and more complicated, making the implementation of these processes an increasingly challenging task. On the one hand, tools and methods exist to describe the business processes. On the other hand, different tools and method exist to describe the IT artifacts implementing them. But a significant gap exists between the two. To overcome this gap, new methodologies are sought. In this paper we discuss a pattern-based modeling and mapping process. Starting from a business process model, which emphasizes the underlying structural process pattern and its associated requirements, we map this model into a corresponding IT model based on nondeterministic automata with state variables. Model checking techniques are used to automatically verify elementary requirements on a process such as the termination and reachability of states. Using an example involving coupled, repetitive activities we discuss the advantages of an iterative process of correcting and refining a model based on insights gained in the interleaved verification steps.

Declarative techniques for model-driven business process integration

Business process integration and automation are among the most significant factors driving the information technology industry today. In addressing the manifold technology challenges of integration and automation, new standardization efforts aim at improving the interoperability of businesses by moving toward a declarative specification of business processes, that is, one which describes what a business process does and not how it is implemented. At the same time, Model Driven Architecture® focuses on improving the software-engineering methods with which business process solutions are implemented by separating the business or application logic from the underlying platform technology and representing this logic with precise semantic models. In this paper, we present an approach to the model-driven generation of programs in the Business Process Execution Language for Web Services (BPEL4WS), which transforms a graphically represented control-flow model into executable code by using techniques that originated in compiler theory. We discuss the underlying algorithms as well as general questions concerning the representation and analysis of model transformations. We study a declarative representation of transformation rules, where preconditions and postconditions are represented in the Object Constraint Language. By adopting a declarative approach, we pave the way for future automatic consistency checking of transformation rules and bidirectional reconciliation of evolving models.

A model-driven transformation method

Model-driven architectures (MDA) separate the business or application logic from the underlying platform technology and represent this logic with precise semantic models. These models are supposed to span the entire life cycle of a software system and ease the software production and maintenance tasks. Consequently, tools will be needed that support these tasks. In this paper, we present a method that implements model-driven transformations between particular platform-independent (business view) and platform-specific (IT architectural) models. On the business level, we focus on business view models expressed in ADF or UML2, whereas on the IT architecture side we focus on service-oriented architectures with Web service interfaces and processes specified in business process protocol languages such as BPEL4WS.

KI 2002: Advances in Artificial Intelligence

This work presents LIGHT, a feature constraint language for deduction-based bottom-up parsing with typed-unification grammars. We overview both its formal definition, as a logic language operating bottom-up inferences over OSF-terms, and its implementation – an elegant combination of a virtual machine for head-corner parsing and an extended abstract machine for feature structure unification.