Rainer Hauser

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.

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.

Compiling Process Graphs into Executable Code

Model-driven architecture envisions a paradigm shift as dramatic as the one from low-level assembler languages to high-level programming languages. In order for this vision to become reality, algorithms are needed that compile models of software systems into deployable and executable implementations. This paper discusses two algorithms that provide such transformations for process graph models in a business process or workflow environment and produce executable programs based on Web services and orchestration languages. The reverse transformations back from executable programs to process graphs are also described.

Untangling Unstructured Cyclic Flows – A Solution Based on Continuations

We present a novel transformation method that allows us to map unstructured cyclic business process models to functionally equivalent workflow specifications that support structured cycles only. Our solution is based on a continuation semantics, which we developed for the graphical representation of a process model. By using a rule-based transformation method originally developed in compiler theory, we can untangle the unstructured flow while solving a set of abstract continuation equations. The generated workflow code can be optimized by controlling the order in which the transformation rules are applied.

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.

A Web Services Matchmaking Engine for Web Services

This paper concentrates on the issue of matchmaking in the context of web services. It provides a brief review of the difference between directory services and matchmaking facilities and explains why directories such as UDDI are important but insufficient for web services and need to be complemented with advanced matchmaking facilities. It discusses the requirements that web services place on matchmaking, namely symmetry of information exchange, the ability of each party to specify requirements of the other party, rich languages to describe services and their consumers as well as their demands, and the ability to dynamically update and configure what is being offered. These requirements are addressed by the Web Services Matchmaking Engine (WSME) – a powerful matchmaking engine capable of matching complex entities, and a Data Dictionary Tool for defining the language of the corresponding matchmaking process. The WSME matchmaking process and property and rules languages are described. An example of how a dynamic market for selling and buying Capacitors can be created with WSME is given. Finally, conclusions and possible future avenues of work are presented.

Using formalized temporal message-flow diagrams

Temporal message‐flow diagrams (TMFDs), alternatively called sequence charts, interaction diagrams, event traces, or actor diagrams, are illustrations of a systems global message‐passing activity over time, and a pictorial aid to understanding the systems behavior. They are widely used for requirements and documentation for network protocols and object‐oriented applications. We present a general formalism for TMFDs, describe a suite of tools we have designed that employs this formalism, and present our experiences with these tools. The formalism and tools described serve to support and broaden the use of TMFDs in developing communicating systems.

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

Timers in OSI protocols-specifications versus implementation

The authors discuss modeling and implementation of timers in OSI protocols. They examine the Estelle, Lotos, and SDL specification languages with emphasis on the features that can be used to express timing. They develop the corresponding models for timer facilities, and discuss possible mechanisms that would support them. As an example drawn from full implementations of the ISO transport and network layers, the authors describe their particular implementation approach for providing timer support.<<ETX>>