Distribution is a major unsolved problem in computer science today. Computers are highly networked, yet programming robust applications that run across the network is difficult or impossible. The goal of the PERDIO project is to provide a system for distributed programming, based on the language Distributed Oz, that will let us program networks of computers as easily as single computers. The major research issues to be resolved in PERDIO are transparency, network awareness, resource management, and fault tolerance.
Distributed Oz is a conservative extension to Oz. It is being developed in a three-year joint project by DFKI (Saarbrücken, Germany) and SICS (Stockholm, Sweden) as an extension to the DFKI Oz system. In Distributed Oz, all network operations are invoked implicitly by the system as an incidental result of using particular language constructs. Extending the implementation of these constructs to a distributed setting is practical because Oz has a simple formal semantics. The resulting system provides transparency, i.e., the same program can run on one site or multiple sites, differing only in performance. For efficiency, it is essential to also have network awareness, i.e., control over network communication patterns. One key idea to achieve this is adding mobility to the language. With this concept, stationary servers and mobile objects are identical in all respects except that they have different (but well-defined) network behavior.
Negra PageNEGRA is an interdisciplinary project carried out in collaboration by the Department of Linguistics and the Department of Computer Science. The aim of the project is to develop a new approach on grammar that integrates language competence and performance, with special attention to linearization phenomena. In the pursuit of this goal, we intend to take full advantage of concurrent constraint programming techniques made possible by Oz and to investigate novel constraint-based formulations of parsing.
NEP PageProgramming models are models of computation which are appropriate as a foundation for the design, the analysis and the implementation of programming languages (consider the lambda calculus for functional programming and SLD resolution for logic programming). A programming model consists of a small number of orthogonal constructs for the modelling of programming abstractions. The starting point for the NEP project is the gamma calculus and the concurrent programming language Oz built on top of it. The gamma calculus is an inherently concurrent programming model which builds on concepts from the pi calculus and from concurrent constraint programming. The gamma calculus subsumes functional computation and allows one to express a variety of programming abstractions. The NEP project will further develop the gamma calculus and the Oz programming model in the following directions: Abstract models for distribution, ressource-sensitive agents, synchronous (reactive) computation, types and type inference, and program equivalences.
CCL PageThe ESPRIT Working Group CCL (see also here) aims to study the construction of computational logics from components. Emphasis is put on the combination of logics and constraint systems. Topics are the combination of logics and constraints of particular interest, the investigation of new symbolic constraints and their combination, and new theorem proving techniques which take advantage of constraints.
Scheduling PageThe aim of this project is to find a schedule for tasks to be sent on a data bus. Tasks may be periodic or aperiodic. The schedule must fit into a given time window, which is repeated with a given frequency on the data bus.
Parallel Oz PageThe goal of this project is to build a parallel implementation of Oz, which makes concurrent activities of an Oz program executing in parallel. The design of the system is targeted for shared-memory parallel architectures. The system will run on a Sun multiprocessor machine (like SPARCenter) under the Solaris operating system.
CHORUS PageThe CHORUS project is a basic research project in the area of natural language semantics. CHORUS is part of the Sonderforschungsbereich 378 - Ressourcenadaptive Kognitive Prozesse (Special Research Department on Resource-adaptive Cognitive Processes) at the University of the Saarland. CHORUS is a joined project between Manfred Pinkal's group in the department of computational linguistics and Gert Smolka's programming systems lab in the department of computer science.
Procope PageThe aim of this project is to establish a cooperation between four research teams in computer science and computational linguistics in France and in Germany, in the general framework of constraint solving.