Daniel Wutke

The Difference Between Graph-Based and Block-Structured Business Process Modelling Languages

The most prominent business process notations in use today are BPMN, EPC and BPEL. While all those languages show similarities on the conceptual level and share similar constructs, the semantics of these constructs and even the intended use of the language itself are often quite different. As a result, users are uncertain when to use which language or construct in a particular language, especially when they have used another business process notation before. In this paper, we discuss the core characteristics of graph-based and block-structured modelling languages and compare them with respect to their join and loop semantics.

Semantic Service Bus: Architecture and Implementation of a Next Generation Middleware

In this paper we present a middleware for the service oriented architecture, called the Semantic Service Bus. It is an advanced middleware possessing enhanced features, as compared to the conventional service buses. It is distinguished by the fact that it uses semantic description of service capabilities, and requirements towards services to enable more elaborate service discovery, selection, routing, composition and data mediation. The contributions of the paper are the conceptual architecture of the Semantic Service Bus and a prototypical implementation supporting different semantic Web service technologies (OWL-S and WSMO) and conventional Web services. Since mission critical application scenarios (for SOA) involve complex orchestrations of services, we have chosen to utilize semantically annotated service orchestrations as the applications to employ this middleware.

Parameterized BPEL processes: concepts and implementation

This paper presents the concept of parameterized WS-flows and two extensions to the BPEL language for enabling it. Another major contribution is a prototypical infrastructure enacting the execution, monitoring and adaptation of parameterized BPEL processes. The advantages of parameterized BPEL processes are the improved flexibility and reusability.

Model and infrastructure for decentralized workflow enactment

Today, enactment of Web service flows -- the process of evaluating control flow and executing activities a workflow is composed of -- is typically done by a centralized workflow enactment service as part of a Workflow management system. This exhibits a number of drawbacks with regard to process adaptability and process fragmentation among a number of participating partners. In order to overcome the deficiencies of centralized process navigation, we propose a model for flexible and adaptable distributed processes as orchestrations of a set of self-coordinating components, without the need for central coordination. Furthermore, we provide key characteristics and an architecture for the development of a supporting infrastructure that facilitates both, deployment and management of distributed components as well as decentralized workflow enactment.

Fault Handling in the Web Service Stack

The Web services platform architecture consists of different layers for exchanging messages. There may be faults happening at each layer during the message exchange. First, the paper presents current standards employed in the different layers and shows their interrelation. Thereby, the focus is on the fault handling strategies. Second, current service middleware is reviewed whether and how it follows the fault handling strategies.

Facilitating complex web service interactions through a tuplespace binding

The SOAP messaging framework, as one key technology of the Web service technology standard stack, defines a standardized message format for Web service interactions, a set of rules governing their processing and a mechanism that describes how SOAP messages can be transmitted over different network transport protocols, called SOAP bindings. The most prominent example for a Web service transport today, is the Hypertext Transfer Protocol (HTTP), which however suffers from certain drawbacks such as being inherently synchronous in nature and not providing decoupling of message sender and receiver in reference or time. In this paper, we present tuplespace technology as an alternative Web service transport that is characterized by a number of properties that are not found in current Web service transports: asynchronism, strong decoupling of sender and receiver and support for advanced message exchange patterns, such as one-to-many interactions, directly on the transport level. We describe the representation of SOAP messages in tuple form and exemplify how to use the operations provided by the tuplespace interface to realize certain Web service message exchange patterns.1

An EAI Pattern-Based Comparison of Spaces and Messaging

Enterprise application integration (EAI) <i>is</i> <i>a</i> <i>major</i> <i>challenge</i> <i>for</i> <i>enterprises</i> <i>to</i> <i>ensure</i> <i>optimal</i> <i>utilization</i> <i>of</i> <i>their</i> <i>landscape</i> <i>of</i> <i>diverse</i> <i>applications</i>. Enterprise application integration patterns help <i>to</i> <i>ease</i> <i>this</i> <i>problem</i> <i>by</i> <i>describing</i> <i>recurring</i> <i>EAI</i> <i>problems</i> <i>and</i> <i>proposing</i> <i>possible</i> <i>solutions.</i> <i>As</i> <i>of</i> <i>today</i>, message-oriented middleware (MOM) <i>is</i> <i>state-</i> <i>of-the-art</i> <i>for</i> <i>EAI</i> <i>integration</i> <i>middleware</i> <i>infrastructures.</i> <i>However</i>, space-based computing (SBC) <i>has</i> <i>been</i> <i>found</i> <i>to</i> <i>offer</i> <i>essentially</i> <i>the</i> <i>same</i> <i>qualities</i> <i>as</i> <i>MOM</i> <i>in</i> <i>terms</i> <i>of</i> <i>asynchronous,</i> <i>reliable</i> <i>and</i> <i>loosely</i> <i>coupled</i> <i>communication</i> <i>and</i> <i>might</i> <i>therefore</i> <i>provide</i> <i>a</i> <i>suitable</i> <i>alternative</i> <i>to</i> <i>MOM</i> <i>in</i> <i>the</i> <i>field</i> <i>of</i> <i>EAI.</i> <i>The</i> <i>objective</i> <i>of</i> <i>this</i> <i>paper</i> <i>is</i> <i>to</i> <i>provide</i> <i>a</i> <i>comparison</i> <i>of</i> <i>MOM</i> <i>and</i> <i>SBC</i> <i>from</i> <i>an</i> <i>applications</i> <i>point</i> <i>of</i> <i>view</i> <i>through</i> <i>an</i> <i>in-depth</i> <i>analysis</i> <i>of</i> <i>EAI</i> <i>patterns,</i> <i>assuming</i> <i>SBC</i> <i>instead</i> <i>of</i> <i>MOM</i> <i>as</i> <i>their</i> <i>underlying</i> <i>middleware</i>.

Towards a digital content services design based on triple space

Digital Asset Management is an emerging business for telecommunication companies, especially when applied to the entertainment market. Current implementations try to overcome the integration needs from each actor participating in the business processes by using Enterprise Application Integration. Triple Space is a space-based communication infrastructure which provides semantic mediation between actors involved in a dialogue. This paper presents a Digital Asset Management use case in which Triple Space will be applied to fulfill the inherent needs of this business domain through the use of this new semantic communication paradigm.

Synchronizing control flow in a tuplespace-based, distributed workflow management system

Decentralized workflow enactment -- the process of evaluating control flow in a distributed manner -- is a key aspect of the implementation of a decentralized workflow management system (WfMS). A major challenge in this field is the support for join operations to synchronize concurrent threads of control flow. The original Linda model however does not provide operations for matching more than one tuple in a single operation -- complex logic needs to be implemented on the client side, having severe impact on performance and breaking the concept of coordination languages by mixing coordination and application logic. In this paper, we stress the need for an extended tuplespace model that natively supports the sync operation realizing WS-BPEL synchronizing joins directly on the tuplespace level. We pay special attention to the description of its semantics and propose an algorithm for efficient implementation on a single tuplespace. For the common case in distributed workflow enactment, where control flow is distributed over multiple tuplespaces, we present an optimization of the aforementioned algorithm in form of the sync pattern.

An Architecture for a QoS-Aware Application Integration Middleware

Complex application integration scenarios often demand for different combinations of qualities of services (QoS) at middleware level. The scenario presented in the paper, for instance, requires transactional middleware behaviour for business negotiations between a relatively small number of participants on the one hand, while on the other hand it requires high scalability for distributing data to a large number of clients. The concept of Triple Space, a semantically enhanced, distributed tuplespace middleware based on an extended Linda model, has been developed to provide such an infrastructure. In contrast to existing middleware infrastructures, Triple Space supports a set of configurations which define the system’s QoS. In this paper, we present a motivating use case scenario, deduce requirements for the architecture of Triple Space, define its architecture and three QoS configurations, and outline our approach towards implementing a highly scalable distributed communication infrastructure.