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## Modeling of Hypermedia Applications

### SOFSEM’ 98: Theory and Practice of Informatics (1998-01-01) 1521: 294-303 , January 01, 1998

This paper introduces the Hypermedia Modeling Language - HML, which constitutes a formal basis for modeling navigation/manipulation, synchronization and media channels handling functionality of applications having some hypermedia features.

We present a logical application architecture framework 1 which forms a principal basis for the HML language. It defines individual hypermedia aspects and determines their position within the application architecture. Using this framework in the application development process improves transparency of the application architecture and leads to a higher degree of reuse and portability as well as to the ease of maintenance of the application.

For each layer of the framework, we discuss basic principles of its modeling in the HML.

## The Computational Description of Analogue System Behaviour

### Prospects for Hardware Foundations (1998-01-01) 1546: 309-332 , January 01, 1998

The aim of this chapter is to define a simple analogue hardware description language L and give it a sound semantics that supports formal reasoning about its properties

The syntax of L is that of a *hybrid* programming languages but the semantics has been derived from the analogue signal semantics of the up-coming IEEE VHDL-AMS extension to the IEEE standard digital hardware description language, VHDL [1].

L will here be given two semantics. Firstly, what may be termed an *exact*, *or hardware*, semantics and secondly an *aproximation, or simulation*, semantics. The simulation semantics is computable and the hardware semantics is not. It will be shown that the simulation semantics approximates the hardware semantics in a well-defined sense. This property is a “no surprises” guarantee with respect to simulation for the language

## Combine & Conquer: Genetic Algorithm and CP for Optimization

### Principles and Practice of Constraint Programming — CP98 (1998-01-01) 1520: 463 , January 01, 1998

We introduce a new optimization method based on a Genetic Algorithm (GA) combined with Constraint Satisfaction Problem (CSP) techniques. The approach is designed for combinatorial problems whose search spaces are too large and/or objective functions too complex for usual CSP techniques and whose constraints are too complex for conventional genetic algorithm. The main idea is the handling of sub-domains of the CSP variables by the genetic algorithm. The population of the genetic algorithm is made up of strings of sub-domains whose adaptation are computed through the resolution of the corresponding ¤b-CSPs’ which are somehow much easier than the original problem. We provide basic and dedicated recombination and mutation operators with various degrees of robustness. The first set of experimentations adresses a naÏve formulation of a Vehicle Routing Problem (VRP). The results are quite encouraging as we outperform CSP techniques and genetic algorithm alone on these formulations

Genetic algorithms are well suited to the quick and global exploration of a large search space to optimize any objective function (even a “black box” one, *i.e.* no hypothesis is required on the function) and are able to provide several solutions of “good quality”.

Constraints satisfaction techniques are fitted to highly constrained problems for which the exhaustive exploration of their search spaces are conceivable. Such a method provides naturally feasible solutions

We suggest to take advantage of the two approaches by combining hybridizing them:

use of constraint satisfaction to compute feasible solutions on a subspace of the search space

use of a genetic algorithm to explore the space formed by the set of these subspaces and perform the optimization

The ratio ρ of the size of a subspace to the size of the whole search space is the essential parameter of the hybridization: one can continuously pass from a pure CSP search (ρ = 1) to a pure stochastic search (ρ = 0, i.e a subspace is reduced to a single value).

## Relations among notions of security for public-key encryption schemes

### Advances in Cryptology — CRYPTO '98 (1998-01-01) 1462: 26-45 , January 01, 1998

We compare the relative strengths of popular notions of security for public key encryption schemes. We consider the goals of privacy and non-malleability, each under chosen plaintext attack and two kinds of chosen ciphertext attack. For each of the resulting pairs of definitions we prove either an implication (every scheme meeting one notion must meet the other) or a separation (there is a scheme meeting one notion but not the other, assuming the first notion can be met at all). We similarly treat plaintext awareness, a notion of security in the random oracle model. An additional contribution of this paper is a new definition of non-malleability which we believe is simpler than the previous one.

## Understanding a Task Model: An Experiment

### People and Computers XIII (1998-01-01): 123-137 , January 01, 1998

The HCI community advocates task analysis as a useful technique for user requirements analysis and system design, and has shown that task models should be developed collaboratively with users. The question of the usability and readability of task models for end-users is therefore an important one. In addition, we were specifically interested in this question in the context of our current project, Isolde*. Isolde is an authoring tool for technical writers whose user interface relies heavily on a specific task notation, DIANE+. We undertook an empirical study aimed at testing the readability and usability of DIANE+. Two experimental tasks are performed by end-users with no previous exposure to task models. Results show that DIANE+ is largely readable but that its usability is somewhat more problematic. This can be attributed to the task description notation rather than to the concepts themselves.

## First Steps in C++ Programming

### Up and Running with C++ (1998-01-01): 9-22 , January 01, 1998

Aims

• To familiarise the reader with the basic structure of a C++ program.

• To introduce the basic data types and the syntax for variable declarations.

• To familiarise the reader with standard input and output in C++.

• To give an understanding and appreciation of the concepts of scope and lifetime.

• To introduce the common operators.

## Nearly optimal language compression using extractors

### STACS 98 (1998-01-01) 1373: 84-93 , January 01, 1998

We show two sets of results applying the theory of extractors to resource-bounded Kolmogorov complexity:

- Most strings in easy sets have nearly optimal polynomial-time *CD* complexity. This extends work of Sipser [Sip83] and Buhrman and Fortnow [BF97].

- We use extractors to extract the randomness of strings. In particular we show how to get from an arbitrary string, an incompressible string which encodes almost as much polynomial-time *CND* complexity as the original string.

## A New and Efficient All-Or-Nothing Disclosure of Secrets Protocol

### Advances in Cryptology — ASIACRYPT’98 (1998-01-01) 1514: 357-371 , January 01, 1998

Two-party protocols have been considered for a long time. Currently, there is a renewed effort to revisit specific protocols to gain efficiency. As an example, one may quote the breakthrough of [BF97], bringing a new solution to the problem of secretly generating RSA keys, which itself goes back to the pioneering work by Yao [Yao86]. The All-Or-Nothing Disclosure of Secrets protocol (ANDOS) was introduced in 1986 by Brassard, Crépeau and Robert [BCR87]. It involves two parties, a vendor and a buyer, and allows the vendor, who holds several secrets, to disclose one of them to the buyer, with the guarantee that no information about the other secrets will be gained. Furthermore, the buyer can freely choose his secret and has the guarantee that the vendor will not be able to find out which secret he picked. In this paper, we present a new protocol which achieves the same functionality, but which is much more efficient and can easily be implemented. Our protocol is especially efficient when a large number of secrets is involved and it can be used in various applications. The proof of security involves a novel use of computational zero-knowledge techniques combined with semantic security.

## Nordic cooperation on Communication and Information Technologies and didactics in education

### Capacity Building for IT in Education in Developing Countries (1998-01-01): 15-25 , January 01, 1998

Implementing and applying each new development in Information Technology (IT) in education is a task requiring considerable resources. At the same time it is obvious that investment in IT is crucial for the development of any nation. The Nordic countries are very small. However, they share cultural backgrounds and educational traditions. Together they constitute a strong block capable of creating and building up expertise in the field of IT. The Nordic Committee on Educational Software and Technology, and, subsequently, IDUN have coordinated the Nordic collaboration during each phase of IT in education.

## A Scalability Scheme for the Real-time Control Protocol

### High Performance Networking (1998-01-01) 8: 153-168 , January 01, 1998

Recently, some problems related to using the Real-time Control Protocol (RTCP) in very large dynamic groups have arisen. Some of these problems are: feedback delay, increasing storage state at every member, and ineffective RTCP bandwidth usage, especially for receivers that obtain incoming RTCP reports through low bandwidth links. In addition, the functionality of some fields (e.g. packet loss fraction) in the Receiver Reports (RRs) becomes questionable as, currently, an increasing number of real-time adaptive applications are using receiver-based rate adaptive schemes instead of rate adaptation schemes based on the sender.

This paper presents the design of a scalable RTCP (S-RTCP) scheme. S-RTCP is based on a hierarchical structure in which members are grouped into local regions. For every region, there is an Aggregator (AG) which receives the RRs sent by its local members. The AG extracts and summarises important information in the RRs, derives some statistics, and sends them to a Manager. The Manager performs additional statistical analysis to monitor the transmission quality and to estimate regions which are suffering massively from congestion.

We believe that our S-RTCP alleviates some of the RTCP scalability problems encountered in very large dynamic groups and makes effective use of RRs with regard to the current changing requirements of real-time adaptive applications in the Internet today.