Algorithms and data structures is the central research area with longest tradition in the section of General Computer Science. A wide spectrum of algorithmic problems have been studied and several top-quality results have been obtained. The work on string matching algorithms (Ukkonen, Tarhio) has been particularly strong and successful. Structural complexity theory (Orponen) and data structures (Nurmi) are other strong areas. Theoretical work has often been conducted within the framework of systems research providing practical motivation for the problems studied. The motivations and applications of the algorithms developed have come e.g. from Prolog implementation and from the problems in biocomputing.
Neural computing and machine learning are active research directions related to artificial intelligence in the section of General Computer Science. In neural computing the two main research topics have been the design and implementation of a high-level knowledge representation language for neural networks that are capable of performing Bayesian reasoning (Myllymäki, Orponen, Tirri), and the complexity theory of neural associative memories (Floréen, Orponen). The machine learning research group (Elomaa, Kivinen, Mannila, Ukkonen) has studied different learning models and the complexity of learning tasks within these models. The more practice-oriented work has developed, for example, new Occam algorithms for learning decision trees and decision lists, and software tools for testing and comparing various machine learning algorithms. Examples of the newest research themes are the investigation into the foundations of genetic algorithms (Floréen), and experiments in predicting the secondary structure of proteins using machine learning methods.
The good reputation of the research work of the section is reflected by the memberships in ESPRIT Working Group 'NeuroCOLT' and in ESPRIT Network of Excellence 'Neuronet', and by several program committee memberships in well-known international conferences.
In the section of Information Systems the research is mostly algorithmic in character. The longest research project concentrates on data mining and machine learning, and it is a joint effort with the section of General Computer Science (see above). Other research projects include relational database design (Mannila), evaluation of Datalog queries (Sippu), text databases (Kilpeläinen, Mannila), computer-supported cooperative work (Erkiö), and knowledge bases (Tirri, Mannila) and knowledge representation (Grahne).
Also in these areas, the work has lead to several joint papers with foreign authors and program committee memberships; the database design work has been published also as a monograph by Addison-Wesley. Recent results include efficient data mining methods for database re-engineering, new efficiently evaluable query languages for text databases, and methods for automatically forming the grammar describing the structure of a text document. The results are published in high-quality journals and conferences.
In the area of programming languages belonging to the section of Computer Software , the theoretical work has focused on syntax analysis, attribute grammars and logic programming. A monograph on parsing theory is an example of significant outcome in this line of work. Several prototype implementations of various software tools have been developed, including programming environments for Prolog and Mode (an experimental object-oriented language) and translator writing systems HLP84, TOOLS, Metauncle, and PROFIT.
In the area of operating systems and performance evaluation, the research was started with a project on program behavior in hierarchical memories. One of the current research directions concentrates on queueing network modeling, centering on the development of new tools and techniques for modeling of real systems.
The main research areas in distributed systems are formal specification of systems and problems of open distributed processing. In the area of formal specifications computer communication protocols and other concurrent systems have been analyzed using various verification tools. Theories and methods relevant to computer aided verification have been studied. Also tools on this area have been implemented. The recurrent theme of research on specifications is to make analysis and verification feasible for real systems. Thus compositional specifications, verification of concurrent systems and minimization of system specifications for analysis are important.
During the last years the importance of distribution has grown immensely. The first project at the department was of constructive nature: we designed and partially implemented an experimental "midware" platform for distributed applications in a heterogeneous environment. The next project, DRYAD, considers an architecture of abstract services. We also have -- as a realization of the idea -- implemented a trading server. Along with these projects we have participated in the ISO standardization work on Open Distributed Processing. Recently a new research line has been opened with the focus on mobile computing. The area of interest is the new functionality needed for of provided by the wireless and mobile data communication, in this case based on NMT-GSM-telephone systems.
Active projects and research areas as well as individual research of some researchers and graduate students are presented in more detail in Section 2.2. Section 2.3 lists a selection of recent publications.