The Association of SIMULA Users is a professional organization concerned with computerized modeling of complex systems as well as the design of software using the Object Oriented Programming (OOP) paradigm. ASU started in 1973 as a group of users of the SIMULA language. SIMULA is the first OOP language and with the exception of Beta programming language, other broadly used OOP languages are conceptual subsets of the SIMULA language whose standard was defined in 1967. Over the years, the ASU expanded its field of interest to encompass software aids and methodologies in design of complex system models. ASU considers OOP more as a way of thinking and viewing the world than as a particular programming technique. ASU organizes annual conferences (1998 Germany, 1999 Hungary, 2000 Malta) and edits a regular Newsletter as a forum for SIMULA users as well as users of other OOP languages. The main interest of ASU members used to be simulation based on advanced OOP techniques like nested classes and nested quasi-parallel systems supported by the SIMULA language and its system class Simulation. The field of interest has gradually expanded to encompass simulation and OOP techniques generally including use of OOP methods in other than strictly OOP environments. Interesting simulation studies are also often presented. A further development of modeling ideas has been emerging during recent years, which is called model oriented programming together with languages that support this type of programming.

The ASU Conferences have always been open to a broad range of topics within the field of computer programming and object oriented modeling and simulation. The application areas have also been from a wide spectrum of professional endeavors. Some of the fields that have been represented are telecommunications, manufacturing, neural networks, ecology, biology, traffic planning, legal systems, limnology, programming languages, railroad management, steel manufacture, optimization strategies and more. We intend to continue with this tradition of inviting presentations from a broad field of subjects.

This year, however, we would like to emphasize that one theme is of special interest, and it is named "model oriented programming". This is in contrast to "object oriented programming" where objects, instances of classes, are the main units used to construct programs and simulation models. Model oriented programming accentuates the idea of using small model units as basic building blocks. A model unit is typically composed of a few objects as well as one or more nested sub-models. Also a model unit usually contains some form of internal behavior with several or many possible courses of action.

Complex technical, ecological and organizational systems are in themselves a set of systems and sub-systems which can be modeled, simulated and studied with good advantage by using software that supports creation of nested and branched system structures. The interest for multilevel, nested and branched program structures extends to the tools and methods used to analyze and structure systems as a first step toward programming dynamic models. One outstanding example is the Unified Modeling Language (UML) as well as the implementations of UML that provide automated diagramming software that allow one to document system structures and program structures. Presentations that deal with these structuring and programming aids are also very interesting subjects at ASU conferences.

Model oriented programming languages (MOPLs) have also been a recurring subject of discussion at recent ASU Conferences. The modeling features built into these languages need to reflect and implement the principles of modeling theory. Both theory and programming language features are interesting subjects for presentations and discussion.

Full original papers in MS Word format are to be sent by e-mail to the ASU Secretariat by July 20th 2001. Papers are usually not more than 10 pages long. Papers will be reviewed by at least two members of the program committee. The authors will be informed about acceptance and about proposed changes (if any) by August 20th 2001. Camera ready papers will be due by September 20th 2001. Those who can not send Word documents by e-mail should contact the local organizer to find an alternative way. To prepare the format details of the paper in a uniform way reference is made to the Instructions for authors.

The conference hotel is the Gärdeby Hotel at Rättvik, Sweden. The hotel is situated about two kilometers to the south east of the town of Rättvik. The hotel is on a large hill overlooking the Lake Siljan to the west. The lake Siljan is formed by the southern depression of a large meteorite crater. This crater was formed about 350 million years ago and is considered to be the third largest meteorite crater on earth. The particular geological formations created by the impact and later geological processes have made this area an ideal testing ground for the deep gas theory. More on that during the conference excursion.

Rättvik is located about 250 km north north-west of Stockholm. Several trains per day travel between Stockholm and Mora, which is the next major town to the west of Rättvik. All trains travel in a tunnel under the Arlanda airport. If you arrive by air it is very easy to take the elevator or escalator down to the trains. There are two tunnels, one for the express trains to Stockholm City and one for the long distance trains. Be sure to descend to the tunnel for long distance trains and take the train going to Mora. Taxi or hotel minibus will be the best way to get between the hotel and train station at Rättvik.

Hotel accommodations will be paid directly by the conference participants. Major credit cards are accepted. For detailed price information please refer to the registration form. A conference delegate whose presentation has been accepted by the conference committee is eligible for a subsidy to cover conference costs. Please contact the ASU Secretariat for more detailed information.