## Institut für Informatik und Computational Science

### Refine

#### Year of publication

#### Document Type

- Article (590) (remove)

#### Keywords

- Didaktik (13)
- Ausbildung (12)
- Hochschuldidaktik (12)
- Informatik (12)
- Answer set programming (5)
- Computer Science Education (4)
- Answer Set Programming (3)
- Competence Measurement (3)
- Secondary Education (3)
- Theory (3)
- answer set programming (3)
- Automata systems (2)
- Big Data (2)
- Competence Modelling (2)
- Computational thinking (2)
- E-Learning (2)
- E-learning (2)
- Informatics Education (2)
- Informatics Modelling (2)
- Informatics System Application (2)
- Informatics System Comprehension (2)
- computational thinking (2)
- cooperating systems (2)
- e-learning (2)
- education (2)
- formal languages (2)
- relevance (2)
- 21st century skills, (1)
- 3D modeling (1)
- 3D visualization (1)
- ABRACADABRA (1)
- AODV (1)
- ARCS Modell (1)
- Abstraction (1)
- Access control (1)
- Achievement (1)
- Active evaluation (1)
- Activity Theory (1)
- Activity-orientated Learning (1)
- Ad hoc routing (1)
- Adaptivity (1)
- Adaptivität (1)
- Arduino (1)
- Assessment (1)
- Audience Response Systeme (1)
- Augmentation (1)
- Austria (1)
- Autismus (1)
- Automated Theorem Proving (1)
- Automatic Item Generation (1)
- Automatisches Beweisen (1)
- Backdoors (1)
- Batch processing (1)
- Berliner Modell (1)
- Blended Learning (1)
- Bloom’s Taxonomy (1)
- Boolean logic models (1)
- CP-Logic (1)
- CS concepts (1)
- Campus (1)
- Capability approach (1)
- Challenges (1)
- Clause Learning (1)
- Cloud (1)
- Cluster Computing (1)
- Cluster computing (1)
- Code generation (1)
- Cognitive Skills (1)
- Coherent phonons (1)
- Combinatorial multi-objective optimization (1)
- Competences (1)
- Competencies (1)
- Complex optimization (1)
- Computational Thinking (1)
- Computational complexity (1)
- Computational grid (1)
- Computer Science (1)
- Computer Science in Context (1)
- Computergestützes Training (1)
- Computing (1)
- Contest (1)
- Context awareness (1)
- Contextualisation (1)
- Contextualized learning (1)
- Continuous Testing (1)
- Continuous Versioning (1)
- Contradictions (1)
- Curriculum (1)
- Curriculum Development (1)
- D-galactosamine (1)
- DPLL (1)
- DRMAA (1)
- DRMS (1)
- Data Analysis (1)
- Data Management (1)
- Data Privacy (1)
- Data federation (1)
- Databases (1)
- Deal of the Day (1)
- Debugging (1)
- Decidability (1)
- Defining characteristics of physical computing (1)
- Design (1)
- Design for testability (DFT) (1)
- Digital Competence (1)
- Digital Education (1)
- Digital Game Based Learning (1)
- Digital Revolution (1)
- Digitale Medien (1)
- Dynamic assessment (1)
- Dynamical X-ray theory (1)
- E-teaching (1)
- Early Literacy (1)
- Educational Standards (1)
- Educational game (1)
- Educational software (1)
- Embedded Systems (1)
- Euclid’s algorithm (1)
- Evaluation (1)
- Event mapping (1)
- Evolution (1)
- Experimentation (1)
- Explore-first Programming (1)
- Extensibility (1)
- Extreme Model-Driven Development (1)
- Facebook (1)
- Fault Localization (1)
- Fibonacci numbers (1)
- Freshmen (1)
- Function (1)
- Fundamental Ideas (1)
- Graphensuche (1)
- Green computing (1)
- Grounded theory (1)
- Heat diffusion (1)
- Hierarchically configurable mask register (1)
- Hochschul-Cloud (1)
- Hochschullehre (1)
- Human Factors (1)
- ICT Competence (1)
- ICT competencies (1)
- ICT skills (1)
- IaaS (1)
- Identifiers (1)
- Image and video stylization (1)
- Incoherent phonons (1)
- Incremental answer set programming (1)
- Informatics (1)
- Information federation (1)
- Information integration (1)
- Information retrieval (1)
- Information security (1)
- Inquiry-based Learning (1)
- Interaktivität (1)
- Interface design (1)
- Job monitoring (1)
- Job submission (1)
- Kernelization (1)
- Key Competencies (1)
- Klausellernen (1)
- Knowledge representation (1)
- Kompetenzerwerb (1)
- L systems (1)
- LMS (1)
- Landmark visibility (1)
- Learners (1)
- Learning Fields (1)
- Learning ecology (1)
- Learning interfaces development (1)
- Learning with ICT (1)
- Lehrer*innenbildung (1)
- Lern-App (1)
- Lernaufgaben (1)
- Lernmotivation (1)
- Load Balancing (1)
- Localization (1)
- Location awareness (1)
- Logarithm (1)
- Logic programming (1)
- Lower Secondary Level (1)
- Loyalty (1)
- MOOCs (1)
- Markov processes (1)
- Masking of X-values (1)
- Massive Open Online Courses (1)
- Measurement (1)
- Meta-Programming (1)
- Mobile application (1)
- Mobile devices (1)
- Mobile learning (1)
- Model checking (1)
- Multiple interpretation scheme (1)
- Music Technology (1)
- N-temperature model (1)
- NUI (1)
- Nash equilibrium (1)
- Natural Science Education (1)
- NoSQL (1)
- Nonmonotonic reasoning (1)
- Norway (1)
- Novice programmers (1)
- OCCI (1)
- OpenOLAT (1)
- Operation problem (1)
- Parallel job execution time estimation (1)
- Parameterized complexity (1)
- Pedagogical content knowledge (1)
- Pedestrian navigation (1)
- Performance Evaluation (1)
- Personalization (1)
- Pervasive computing (1)
- Pervasive game (1)
- Pervasive learning (1)
- Physical Science (1)
- Preference Handling (1)
- Preprocessing (1)
- Problem Solving (1)
- Process mining (1)
- Process model analysis (1)
- Product lifecycle management (1)
- Prototyping (1)
- REST (1)
- RSA triangle (1)
- Ranking (1)
- Recommendations for CS-Curricula in Higher Education (1)
- Relevanz (1)
- SAT (1)
- SOA (1)
- SaaSAbstract (1)
- Seamless learning (1)
- Semantic data (1)
- Semantic web (1)
- Sensors (1)
- Service orientation (1)
- Signaling transduction networks (1)
- Small Private Online Courses (1)
- Social (1)
- Statistical relational learning (1)
- Stochastic relational process (1)
- Strategie (1)
- Structural equation modeling (1)
- Systems biology (1)
- TPACK (1)
- Tasks (1)
- Teacher perceptions (1)
- Teachers (1)
- Teaching information security (1)
- Technology proficiency (1)
- Terminology (1)
- Tests (1)
- Theorembeweisen (1)
- Thermoelasticity (1)
- Time series (1)
- Tracking (1)
- Ubiquitous learning (1)
- Ultrafast dynamics (1)
- Unary languages (1)
- Unifikation (1)
- Uniform Access Principle (1)
- Usability testing (1)
- User Experience (1)
- User submission pattern (1)
- User-centred design (1)
- Verification (1)
- Vocational Education (1)
- Weiterbildung (1)
- Wireless Sensor Networks (1)
- X-masking (1)
- X-values (1)
- Young People (1)
- abstraction (1)
- acute liver failure (1)
- adversarial classification (1)
- algorithm schedules (1)
- analogical thinking (1)
- artistic rendering (1)
- behavioral abstraction (1)
- belief merging (1)
- belief revision (1)
- binary representation (1)
- binary search (1)
- bioinformatics (1)
- block representation (1)
- bootstrapping (1)
- cellular automata (1)
- classroom language (1)
- code generation (1)
- cognitive modifiability (1)
- collaborative learning (1)
- combined task and motion planning (1)
- competence (1)
- competencies (1)
- competency (1)
- complexity (1)
- comprehension (1)
- computer science education (1)
- computer science teachers (1)
- conductive argument (1)
- consistency (1)
- consistency checking (1)
- consistency measures (1)
- controlled vocabularies (1)
- course timetabling (1)
- cs4fn (1)
- curriculum theory (1)
- decidability questions (1)
- declarative problem solving (1)
- diagnosis (1)
- didactics (1)
- didaktisches Konzept (1)
- digitale Bildung (1)
- digitale Medien (1)
- digitally-enabled pedagogies (1)
- divide and conquer (1)
- domain-specific APIs (1)
- dynamic service binding (1)
- e-mentoring (1)
- eLectures (1)
- education and public policy (1)
- educational programming (1)
- educational systems (1)
- educational timetabling (1)
- edutainment (1)
- endothelin (1)
- endothelin-converting enzyme (1)
- environments (1)
- evolution (1)
- exponentiation (1)
- external ambiguity (1)
- finite model computation (1)
- formal argumentation systems (1)
- fun (1)
- geovisualization (1)
- graph-search (1)
- high school (1)
- higher (1)
- higher education (1)
- informal and formal learning (1)
- informal logic (1)
- informatics (1)
- informatics education (1)
- innovation (1)
- interactive course (1)
- interactive workshop (1)
- internal ambiguity (1)
- key competences in physical computing (1)
- key competencies (1)
- kidney cancer (1)
- kinaesthetic teaching (1)
- klinisch-praktischer Unterricht (1)
- learning (1)
- loop formulas (1)
- loose programming (1)
- manipulation planning (1)
- mediated learning experience (1)
- metabolism (1)
- metabolomics (1)
- metadata (1)
- metastasis (1)
- mobile learning (1)
- mobile technologies and apps (1)
- mobiles Lernen (1)
- natural language generation (1)
- neighborhood (1)
- networks (1)
- neutral endopeptidase (1)
- nonphotorealistic rendering (NPR) (1)
- o-ambiguity (1)
- open learning (1)
- operating system (1)
- organisational evolution (1)
- paper prototyping (1)
- parameter (1)
- pedagogy (1)
- personal (1)
- personal response systems (1)
- philosophical foundation of informatics pedagogy (1)
- physical computing tools (1)
- plug-ins (1)
- portfolio-based solving (1)
- pre-primary level (1)
- premise acceptability (1)
- preprocessing (1)
- primary education (1)
- primary level (1)
- problem-solving (1)
- process model alignment (1)
- process modeling (1)
- professional development (1)
- program encodings (1)
- programming (1)
- programming in context (1)
- proof complexity (1)
- quantum (1)
- real arguments (1)
- reference (1)
- referential effectiveness (1)
- regular language (1)
- secondary computer science education (1)
- secondary education (1)
- self-efficacy (1)
- semantic web (1)
- simplicity (1)
- social media (1)
- stable model semantics (1)
- static prediction games (1)
- strong equivalence (1)
- student activation (1)
- student experience (1)
- student perceptions (1)
- students’ conceptions (1)
- students’ knowledge (1)
- sufficiency (1)
- tableau calculi (1)
- teacher competencies (1)
- teaching informatics in general education (1)
- technische Rahmenbedingungen (1)
- tele-teaching (1)
- test response compaction (1)
- theorem (1)
- theory of computation (1)
- tools (1)
- tracing (1)
- triangulated irregular networks (1)
- unfounded sets (1)
- unification (1)
- user-centred (1)
- video annotation (1)
- virtual reality (1)
- xAPI (1)
- ‘unplugged’ computing (1)

In this paper we introduce and study some new cooperation protocols for cooperating distributed (CD) grammar systems. These derivation modes depend on the number of different nonterminals present in the sentential form obtained when a component finished a derivation phase. This measure describes the competence of the grammar on the string (the competence is high if the number of the different nonterminals is small). It is also a measure of the efficiency of the grammar on the given string (a component is more efficient than another one if it is able to decrease the number of nonterminals in the string to a greater extent). We prove that if the underlying derivation mode is the t-mode derivation, then some variants of these systems determine the class of random context ET0L languages. If these CD grammar systems use the k step limited derivations as underlying derivation mode, then they are able to generate any recursively enumerable language.

We define H- and EH-expressions as extensions of regular expressions by adding homomorphic and iterated homomorphic replacement as new operations, resp. The definition is analogous to the extension given by Gruska in order to characterize context-free languages. We compare the families of languages obtained by these extensions with the families of regular, linear context-free, context-free, and EDT0L languages. Moreover, relations to language families based on patterns, multi-patterns, pattern expressions, H-systems and uniform substitutions are also investigated. Furthermore, we present their closure properties with respect to TRIO operations and discuss the decidability status and complexity of fixed and general membership, emptiness, and the equivalence problem.

Existing telecommunication networks and classical roles of operators are subject to fundamental change. Many network operators are currently seeking for new sources to generate revenue by exposing network capabilities to 3rd party service providers. At the same time we can observe that services on the World Wide Web (WWW) are becoming mature in terms of the definition of APIs that are offered towards other services. The combinations of those services are commonly referred to as Web 2.0 mash-ups. Rapid service design and creation becomes therefore important to meet the requirements in a changing technology and competitive market environment. This report describes our approach to include Next Generation Networks (NGN)-based telecommunications application enabler into complex services by defining a service broker that mediates between 3rd party applications and NGN service enablers. It provides policy-driven orchestration mechanisms for service enablers, a service authorization functionality, and a service discovery interface for Service Creation Environments. The work has been implemented as part of the Open SOA Telco Playground testbed at Fraunhofer FOKUS.

We discuss the relaxation of a class of nonlinear elliptic Cauchy problems with data on a piece S of the boundary surface by means of a variational approach known in the optimal control literature as "equation error method". By the Cauchy problem is meant any boundary value problem for an unknown function y in a domain X with the property that the data on S, if combined with the differential equations in X, allow one to determine all derivatives of y on S by means of functional equations. In the case of real analytic data of the Cauchy problem, the existence of a local solution near S is guaranteed by the Cauchy-Kovalevskaya theorem. We also admit overdetermined elliptic systems, in which case the set of those Cauchy data on S for which the Cauchy problem is solvable is very "thin". For this reason we discuss a variational setting of the Cauchy problem which always possesses a generalised solution.

Owing to the loose coupling between replicas, the replica-exchange (RE) class of algorithms should be able to benefit greatly from using as many resources as available. However, the ability to effectively use multiple distributed resources to reduce the time to completion remains a challenge at many levels. Additionally, an implementation of a pleasingly distributed algorithm such as replica-exchange, which is independent of infrastructural details, does not exist. This paper proposes an extensible and scalable framework based on Simple API for Grid Applications that provides a general-purpose, opportunistic mechanism to effectively use multiple resources in an infrastructure-independent way. By analysing the requirements of the RE algorithm and the challenges of implementing it on real production systems, we propose a new abstraction (BIGJOB), which forms the basis of the adaptive redistribution and effective scheduling of replicas.

Two mapping populations of a cross between the Arabidopsis thaliana accessions Col-0 and C24 were cultivated and analyzed with respect to the levels of 181 metabolites to elucidate the biological phenomenon of heterosis at the metabolic level. The relative mid-parent heterosis in the F-1 hybrids was <20% for most metabolic traits. The first mapping population consisting of 369 recombinant inbred lines (RILs) and their test cross progeny with both parents allowed us to determine the position and effect of 147 quantitative trait loci (QTL) for metabolite absolute mid-parent heterosis (aMPH). Furthermore, we identified 153 and 83 QTL for augmented additive (Z(1)) and dominance effects (Z(2)), respectively. We identified putative candidate genes for these QTL using the ARACYC database (http://www.arabidopsis.org/ biocyc), and calculated the average degree of dominance, which was within the dominance and over-dominance range for most metabolites. Analyzing a second population of 41 introgression lines (ILs) and their test crosses with the recurrent parent, we identified 634 significant differences in metabolite levels. Nine per cent of these effects were classified as over-dominant, according to the mode of inheritance. A comparison of both approaches suggested epistasis as a major contributor to metabolite heterosis in Arabidopsis. A linear combination of metabolite levels was shown to significantly correlate with biomass heterosis (r = 0.62).

This paper presents a concept for automated architecture synthesis for adaptive multiprocessors on chip, in particular for Field-Programmable Gate-Array (FPGA) devices. Given a parallel program, the intent is to simultaneously allocate processor resources and the corresponding communication network, and at the same time, to map the parallel application to get an optimum application-specific architecture. This approach builds up on a previously proposed design platform that automates system integration and FPGA synthesis for such architectures. As a result, the overall concept offers an automated design approach from application mapping to system and FPGA configuration. The automated synthesis is based on combinatorial optimization. Automation is possible because a solvable Integer Linear Programming (ILP) model that captures all necessary design trade-off parameters of such systems has been found. Experimental results to study the feasibility of the automated synthesis indicate that problems with sizes that can be encountered in the embedded domain can be readily solved. Results obtained underscore the need for an automated synthesis for design space exploration.

Using the timing flexibility of modern automatic test equipment (ATE) test response data can be compacted without the need for additional X-masking logic. In this article the test response is compacted by several multiple input shift registers without feedback (NF-MISR). The shift registers are running on a k-times higher clock frequency than the test clock. For each test clock cycle only one out of the k outputs of each shift register is evaluated by the ATE. The impact of consecutive X values within the scan chains is reduced by a periodic permutation of the NF-MISR inputs. As a result, no additional external control signals or test set dependent control logic is required. The benefits of the proposed method are shown by the example of an implementation on a Verigy ATE. Experiments on three industrial circuits demonstrate the effectiveness of the proposed approach in comparison to a commercial DFT solution.

Answer set programming (ASP) does not allow for incrementally constructing answer sets or locally validating constructions like proofs by only looking at a part of the given program. In this article, we elaborate upon an alternative approach to ASP that allows for incremental constructions. Our approach draws its basic intuitions from the area of default logics. We investigate the feasibility of the concept of semi-monotonicity known from default logics as a basis of incrementality. On the one hand, every logic program has at least one answer set in our alternative setting, which moreover can be constructed incrementally based on generating rules. On the other hand, the approach may produce answer sets lacking characteristic properties of standard answer sets, such as being a model of the given program. We show how integrity constraints can be used to re-establish such properties, even up to correspondence with standard answer sets. Furthermore, we develop an SLD-like proof procedure for our incremental approach to ASP, which allows for query-oriented computations. Also, we provide a characterization of our definition of answer sets via a modification of Clarks completion. Based on this notion of program completion, we present an algorithm for computing the answer sets of a logic program in our approach.

We study the complexity of two-person constraint satisfaction games. An instance of such a game is given by a collection of constraints on overlapping sets of variables, and the two players alternately make moves assigning values from a finite domain to the variables, in a specified order. The first player tries to satisfy all constraints, while the other tries to break at least one constraint: the goal is to decide whether the first player has a winning strategy. We show that such games can be conveniently represented by a logical form of quantified constraint satisfaction, where an instance is given by a first-order sentence in which quantifiers alternate and the quantifier-free part is a conjunction of (positive) atomic formulas; the goal is to decide whether the sentence is true. While the problem of deciding such a game is PSPACE-complete in general, by restricting the set of allowed constraint predicates, one can obtain infinite classes of constraint satisfaction games of lower complexity. We use the quantified constraint satisfaction framework to study how the complexity of deciding such a game depends on the parameter set of allowed predicates. With every predicate. one can associate certain predicate-preserving operations, called polymorphisms. We show that the complexity of our games is determined by the surjective polymorphisms of the constraint predicates. We illustrate how this result can be used by identifying the complexity of a wide variety of constraint satisfaction games.

We investigate the descriptional complexity of the nondeterministic finite automaton (NFA) to the deterministic finite automaton (DFA) conversion problem, for automata accepting subregular languages such as combinational languages, definite languages and variants thereof, (strictly) locally testable languages, star-free languages, ordered languages, prefix-, suffix-, and infix-closed languages, and prefix-, Suffix-, and infix-free languages. Most of the bounds for the conversion problem are shown to be tight ill the exact number of states, that is, the number is sufficient and necessary in the worst case. Otherwise tight bounds in order of magnitude are shown.

We address classification problems for which the training instances are governed by an input distribution that is allowed to differ arbitrarily from the test distribution-problems also referred to as classification under covariate shift. We derive a solution that is purely discriminative: neither training nor test distribution are modeled explicitly. The problem of learning under covariate shift can be written as an integrated optimization problem. Instantiating the general optimization problem leads to a kernel logistic regression and an exponential model classifier for covariate shift. The optimization problem is convex under certain conditions; our findings also clarify the relationship to the known kernel mean matching procedure. We report on experiments on problems of spam filtering, text classification, and landmine detection.

We introduce and investigate input-revolving finite automata, which are (nondeterministic) finite state automata with the additional ability to shift the remaining part of the input. Three different modes of shifting are considered, namely revolving to the left, revolving to the right, and circular-interchanging. We investigate the computational capacities of these three types of automata and their deterministic variants, comparing any of the six classes of automata with each other and with further classes of well-known automata. In particular, it is shown that nondeterminism is better than determinism, that is, for all three modes of shifting there is a language accepted by the nondeterministic model but not accepted by any deterministic automaton of the same type. Concerning the closure properties most of the deterministic language families studied are not closed under standard operations. For example, we show that the family of languages accepted by deterministic right-revolving finite automata is an anti-AFL which is not closed under reversal and intersection.

(Near-)inverses of sequences
(2006)

We introduce the notion of a near-inverse of a non-decreasing sequence of positive integers; near-inverses are intended to assume the role of inverses in cases when the latter cannot exist. We prove that the near-inverse of such a sequence is unique; moreover, the relation of being near-inverses of each other is symmetric, i.e. if sequence g is the near-inverse of sequence f, then f is the near-inverse of g. There is a connection, by approximations, between near- inverses of sequences and inverses of continuous strictly increasing real-valued functions which can be exploited to derive simple expressions for near-inverses

A brain-computer interface (BCI) is a system that allows its users to control external devices with brain activity. Although the proof-of-concept was given decades ago, the reliable translation of user intent into device control commands is still a major challenge. Success requires the effective interaction of two adaptive controllers: the user's brain, which produces brain activity that encodes intent, and the BCI system, which translates that activity into device control commands. In order to facilitate this interaction, many laboratories are exploring a variety of signal analysis techniques to improve the adaptation of the BCI system to the user. In the literature, many machine learning and pattern classification algorithms have been reported to give impressive results when applied to BCI data in offline analyses. However, it is more difficult to evaluate their relative value for actual online use. BCI data competitions have been organized to provide objective formal evaluations of alternative methods. Prompted by the great interest in the first two BCI Competitions, we organized the third BCI Competition to address several of the most difficult and important analysis problems in BCI research. The paper describes the data sets that were provided to the competitors and gives an overview of the results.

We consider the problem of representing arbitrary preferences in causal reasoning and planning systems. In planning, a preference may be seen as a goal or constraint that is desirable, but not necessary, to satisfy. To begin, we define a very general query language for histories, or interleaved sequences of world states and actions. Based on this, we specify a second language in which preferences are defined. A single preference defines a binary relation on histories, indicating that one history is preferred to the other. From this, one can define global preference orderings on the set of histories, the maximal elements of which are the preferred histories. The approach is very general and flexible; thus it constitutes a base language in terms of which higher-level preferences may be defined. To this end, we investigate two fundamental types of preferences that we call choice and temporal preferences. We consider concrete strategies for these types of preferences and encode them in terms of our framework. We suggest how to express aggregates in the approach, allowing, e.g. the expression of a preference for histories with lowest total action costs. Last, our approach can be used to express other approaches and so serves as a common framework in which such approaches can be expressed and compared. We illustrate this by indicating how an approach due to Son and Pontelli can be encoded in our approach, as well as the language PDDL3.

The ellipticity of operators on a manifold with edge is defined as the bijectivity of the components of a principal symbolic hierarchy sigma = (sigma(psi), sigma(boolean AND)), where the second component takes values in operators on the infinite model cone of the local wedges. In the general understanding of edge problems there are two basic aspects: Quantisation of edge-degenerate operators in weighted Sobolev spaces, and verifying the ellipticity of the principal edge symbol sigma(boolean AND) which includes the (in general not explicity known) number of additional conditions of trace and potential type on the edge. We focus here on these questions and give explicit answers for a wide class of elliptic operators that are connected with the ellipticity of edge boundary value problems and reductions to the boundary. In particular, we study the edge quantisation and ellipticity for Dirichlet-Neumann operators with respect to interfaces of some codimension on a boundary. We show analogues of the Agranovich-Dynin formula for edge boundary value problems.

Computational analysis of virtual team collaboration in teh early stages of engineering design
(2010)

We propose simple and fast methods based on nearest neighbors that order objects from high-dimensional data sets from typical points to untypical points. On the one hand, we show that these easy-to-compute orderings allow us to detect outliers (i.e. very untypical points) with a performance comparable to or better than other often much more sophisticated methods. On the other hand, we show how to use these orderings to detect prototypes (very typical points) which facilitate exploratory data analysis algorithms such as noisy nonlinear dimensionality reduction and clustering. Comprehensive experiments demonstrate the validity of our approach.

In this paper we present the design and implementation of the Migol brokering framework. Migol is a Grid middleware, which addresses the fault-tolerance of long-running and compute-intensive applications. The framework supports e. g. the automatic and transparent recovery respectively the migration of applications. Another core feature of Migol is the discovery, selection, and allocation of resources using advance reservation. Grid broker systems can significantly benefit from advance reservation. With advance reservation brokers and users can obtain execution guarantees from local resource management systems (LRM) without requiring detailed knowledge of current and future workloads or of the resource owner's policies. Migol's Advance Reservation Service (ARS) provides an adapter layer for reservation capabilities of different LRMs, which is currently not provided by existing Grid middleware platforms. Further, we propose a shortest expected delay (SED) strategy for scheduling of advance reservations within the Job Broker Service. SED needs information about the earliest start time of an application. This is currently not supported by LRMs. We added this feature for PBSPro. Migol depends on Globus and its security infrastructure. Our performance experiments show the substantial overhead of this serviceoriented approach.

Today, InfiniBand is an evolving high speed interconnect technology to build high performance computing clusters, that achieve top 10 rankings in the current top 500 of the worldwide fastest supercomputers. Network interfaces (called host channel adapters) provide transport layer services over connections and datagrams in reliable or unreliable manner. Additionally, InfiniBand supports remote direct memory access (RDMA) primitives that allow for one- sided communication. Using server load balancing together with a high performance cluster makes it possible to build a fast, scalable, and reliable service infrastructure. We have designed and implemented a scalable load balancer for InfiniBand clusters called SLIBNet. Our investigations show that the InfiniBand architecture offers features which perfectly support load balancing. We want to thank the Megware Computer GmbH for providing us an InfiniBand switch to realize a server load balancing testbed.

ESF-Abschlußbericht
(1994)

Molecular dynamics simulation of the association of model colloidal particles in two dimensions
(1995)

Novel verification framework combining structural and OBDD methods in a synthesis environment
(1995)

Software development plan
(1996)