Workflow and Process Synchronization with Interaction Expressions and Graphs

Current workflow management technology does not provide adequate means for inter-workflow coordination as concurrently executing workflows are considered completely independent. While this simplified view might suffice for one application domain or the other, there are many real-world application scenarios where workflows −− though independently modeled in order to remain comprehensible and manageable −− are semantically interrelated. As pragmatical approaches, like merging interdependent workflows or inter-workflow message passing, do not satisfactorily solve the inter-workflow coordination problem, interaction expressions and graphs are proposed as a simple yet powerful formalism for the specification and implementation of synchronization conditions in general and inter-workflow dependencies in particular. In addition to a graph-based semi-formal interpretation of the formalism, a precise formal semantics, an equivalent operational semantics, an efficient implementation of the latter, and detailed complexity analyses have been developed allowing the formalism to be actually applied to solve real-world problems like inter-workflow coordination

Interaction Expressions - A Powerful Formalism for Describing Inter-Workflow Dependencies

Current workflow management technology does not provide adequate means for describing and implementing workflow ensembles, i. e., dynamically evolving collections of more or less independent workflows which have to synchronize only now and then. Interaction expressions are proposed as a simple yet powerful formalism to remedy this shortcoming. Besides operators for sequential composition, iteration, and selection, which are well-known from regular expressions, they provide parallel composition and iteration, conjunction, and several advanced features like parametric expressions, multipliers, and quantifiers. The paper introduces interaction expressions semi-formally, gives examples of their typical use, and describes their implementation and integration with state-of-the-art workflow technology. Major design principles, such as orthogonality and implicit and predictive choice, are discussed and compared with several related approaches

Monolithic Overlapping Schwarz Domain Decomposition Methods with GDSW Coarse Spaces for Saddle Point Problems

Monolithic overlapping Schwarz preconditioners for saddle point problems of Stokes, Navier-Stokes, and mixed linear elasticity ty e are presented. For the first time, coarse spaces obtained from the GDSW (Generalized Dryja-Smith-Widlund) approach are used in such a setting. Numerical results of our parallel implementation are presented for several model problems. In particular, cases are considered where the problem cannot or should not b e reduced using local static condensation, e.g., Stokes, Navier-Stokes or mixed elasticity problems with continuous pressure spaces. In the new monolithic preconditioners, the local overlapping problems and the coarse problem are saddle point problems with the same structure as the original problem. Our parallel implementation of these preconditioners is based on the FROSch (Fast and Robust Overlapping Schwarz) library, which is part of the Trilinos package ShyLU. The implementation is algebraic in the sense that the preconditioners can be constructed from the fully assembled stiffness matrix and information about the block structure of the problem. Parallel scalability results for several thousand cores for Stokes, Navier-Stokes, and mixed linear elasticity model problems are reported. Each of the local problems is solved using a direct solver in serial mo de, whereas the coarse problem is solved using a direct solver in serial or MPI-parallel mode or using an MPI-parallel iterative Krylov solve

Representation of Medical Guidelines Using a Classification-Based System

Medical guidelines play an increasing role in selecting diag-nostic and therapeutic steps under the aspects of effectiveness, invasiveness, and costs. To work directly on patient data already available in electronic form, they should be integrated into a medical Information System. In order to develop a "medical guideline module" (MGM) managing and applying guidelines to patients, a "knowledge level" representation of guidelines is necessary which reflects the structure of medical knowledge and matches medical processes. Furthermore, a direct transformation to the "symbol level" is needed. We use a nested, frame-like structure on the knowledge level and show that a classification-based knowledge representation system (CBKRS) is principally well suited for the symbol level. To facilitate the usage and to be independent of a particular CBKRS, we introduce an intermediate level called "intelligent object system" (IOS). It is developed by augmenting a simple data model for describing complex objects with prototypes and implications as a means to classify objects and to draw inferences based on this Classification. Finally, the transformation of guidelines to prototypes and implications is described

Workflow- und Prozeßsynchronisation mit Interaktionsausdrücken und -graphen

Im Rahmen der Arbeit werden Interaktionsausdrücke und -graphen als deskriptiver Formalismus zur kompakten, übersichtlichen und modularen Spezifikation sowie zur effizienten Implementierung von Synchronisationsbedingungen unterschiedlichster Art konzipiert, theoretisch untersucht, praktisch implementiert und prototypisch zur Synchronisation von Workflows angewandt

Sprachtheoretische Semantik von Interaktionsausdrücken

Dieser Bericht definiert Interaktionsausdrücke, wie sie in den Berichten „Grundlagen von Interaktionsausdrücken“ (UIB 97-09) und “Interaction Expressions −− A Powerful Formalism for Describing Inter-Workflow Dependencies” (UIB 97-04) beschrieben sind, mittels ihrer sprachtheoretischen Semantik. Nach einer kurzen Definition der wichtigsten Grundbegriffe werden in Abschnitt 2 zunächst reguläre Ausdrücke, die eine Teilmenge von Interaktionsausdrücken darstellen, mittels ihrer sprachtheoretischen Semantik definiert. Anschließend wird diese Definition auf elementare Interaktionsausdrücke erweitert und ein erster Versuch zur Definition von Quantoren unternommen. Abschnitt 3 zeigt jedoch Schwierigkeiten und Grenzen dieser „traditionellen“ Vorgehensweise auf, so daß in Abschnitt 4 eine „revidierte“ Definition von Interaktionsausdrücken gegeben wird, die im wesentlichen auf einer sauberen Trennung von vollständigen und teilweisen Worten basiert. Alle wesentlichen Definitionen werden jeweils durch Beispiele illustriert, um die abstrakten Konzepte ein wenig „greifbarer“ zu machen

Grundlagen von Interaktionsausdrücken

Dieser Bericht stellt eine umfassende Einführung in die Grundlagen von Interaktionsausdrücken dar und dient damit gleichermaßen als „Tutorium“ und als „Referenzhandbuch“ zu diesem Formalismus. Obwohl Interaktionsausdrücke primär mit der Zielsetzung entwickelt wurden, einen geeigneten Formalismus zur Beschreibung (und Implementierung) von Inter-Workflow-Abhängigkeiten zur Verfügung zu stellen, ist ihre Anwendbarkeit nicht auf dieses spezielle Gebiet beschränkt. Vielmehr stellen sie einen sehr allgemeinen Formalismus zur Beschreibung (und damit zur Lösung) nahezu beliebiger Synchronisationsprobleme dar. Aus diesem Grund werden Interaktionsausdrücke in diesem Bericht unabhängig von der speziellen Anwendungsdomäne Inter-Workflow-Abhängigkeiten eingeführt und mit Beispielen aus ganz unterschiedlichen Bereichen veranschaulicht

Graphische Repräsentation von Interaktionsausdrücken

Dieser Bericht stellt eine einfache graphische Notation für Interaktionsausdrücke vor, wie sie in den Berichten „Grundlagen von Interaktionsausdrücken“ (UIB 97-09) und “Interaction Expressions −− A Powerful Formalism for Describing Inter-Workflow Dependencies” (UIB 97-04) beschrieben sind

Intelligent Prefetching and Buffering for Interactive Streaming of MPEG Videos

Continuous delivery of media streams like video over IP networks so far is mainly handled by commercial approaches that deliver the stream forward-oriented in their own proprietary format. Though some existing streaming technologies are able to adapt to varying bandwidths, they do not provide smooth reactions to user interactions with the continuous stream. We have developed the MPEG-L/MRP strategy, an adaptive prefetching algorithm for the MPEG-1 video format in combination with an intelligent buffering technique that allows for smooth and quick reactions to user interactions with the stream. With L/MRP [12] an approach already has been presented to deliver and buffer homogeneous continuous data streams like Motion-JPEG with special focus on fast reaction to user interactions. In contrast, the MPEG-1 encoding with its different frame types and the dependencies between frames opens the door to a more �ne-grained adaptation of the continous stream. However, the complexity of MPEG-1 calls for comprehensive adaptation and special amendments of the L/MRP algorithm to make it an eÆcient preloading and buffering technique for MPEG-1 videos. With the realization of MPEG-L/MRP in the context of a multimedia presentation engine on top of a multimedia repository we have an efficient means to deliver continuous streams of interactive multimedia presentations over existing IP infrastructure trying to minimize interaction response time and optimize loading/reloading portions of a video stream