Jussi Vanhatalo

Faster and More Focused Control-Flow Analysis for Business Process Models Through SESE Decomposition

We present a technique to enhance control-flow analysis of business process models. The technique considerably speeds up the analysis and improves the diagnostic information that is given to the user to fix control-flow errors. The technique consists of two parts: Firstly, the process model is decomposed into single-entry-single-exit (SESE) fragments, which are usually substantially smaller than the original process. This decomposition is done in linear time. Secondly, each fragment is analyzed in isolation using a fast heuristic that can analyze many of the fragments occurring in practice. Any remaining fragments that are not covered by the heuristic can then be analyzed using any known complete analysis technique. We used our technique in a case study with more than 340 real business processes modeled with the IBM WebSphere Business Modeler. The results suggest that control-flow analysis of many real process models is feasible without significant delay (less than a second). Therefore, control-flow analysis could be used frequently during editing time, which allows errors to be caught at earliest possible time.

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.

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.

Automatic Workflow Graph Refactoring and Completion

Workflow graphs are used to model the control flow of business processes in various languages, e.g., BPMN, EPCs and UML activity diagrams. We present techniques for automatic workflow graph refactoring and completion. These techniques enable various use cases in modeling and runtime optimization. For example they allow us to complete a partial workflow graph, they provide local termination detection for workflow graphs with multiple ends, and they allow us to execute models containing OR-joins faster. Some of our techniques are based on workflow graph parsing and the Refined Process Structure Tree [10].

An Incremental Approach to the Analysis and Transformation of Workflows Using Region Trees

The analysis of workflows in terms of structural correctness is important for ensuring the quality of workflow models. Typically, this analysis is only one step in a larger development process, followed by further transformation steps that lead from high-level models to more refined models until the workflow can finally be deployed on the underlying workflow engine of the production system. For practical and scalable applications, both analysis and transformation of workflows must be integrated to allow incremental changes of larger workflows. In this paper, we introduce the concept of a region tree (RT) for workflow models that can be used as the central data structure for both workflow analysis and workflow transformation. An RT is similar to a program structure tree and imposes a hierarchy of regions as an overlay structure onto the workflow model. It allows an incremental approach to the analysis and transformation of workflows, and thereby, significantly reduces the overhead because individual regions can be dealt with separately. The RT is built using a set of region-growing rules. The set of rules presented here is shown to be correct and complete in the sense that a workflow is region-reducible as defined through these rules if and only if it is semantically sound.

Combining Analysis of Unstructured Workflows with Transformation to Structured Workflows

Analysis of workflows in terms of structural correctness is important for ensuring the quality of workflow models. Typically, this analysis is only one step in a larger development process, followed by further transformation steps that lead from high-level models to more refined models until the workflow can finally be deployed on the underlying workflow engine of the production system. For practical and scalable applications, analysis and transformations of workflows must both be integrated to allow incremental changes of larger workflows. In this paper, we introduce the concept of a region tree for workflow models that can be used as the central data structure for both workflow analysis and workflow transformation. A region tree is similar to a program structure tree and imposes a hierarchy of regions onto the workflow model. It allows an incremental approach to analysis and transformation of workflows and thereby significantly reduces the overhead because individual regions can be dealt with separately

Combining Quality Assurance and Model Transformations in Business-Driven Development

Business-driven development is a methodology for developing IT solutions that directly satisfy business requirements. At its core are business processes, which are usually modeled by combining graphical and textual notations. During business-driven development, business process models are taken to the IT level, where they are implemented in a Service-Oriented Architecture. A major challenge in business-driven development is the semantic gap between models captured at the business and the IT level. Model transformations play a major role in bridging this gap. This paper presents a transformation framework for IBM WebSphere Business Modeler that enables programmers to quickly develop in-place model transformations, which are then made available to users of this tool. They address various user needs such as quickly correcting modeling errors, refining a process model, or applying a number of refactoring operations. Transformations are combined with quality assurance techniques, which help users to preserve or improve the correctness of their business process models when applying transformations.