Spatio-temporal databases deal with geometries changing over time. The goal of our work is to provide a DBMS data model and query language capable of handling such time-dependent geometries, including those changing continuously which describe moving objects. Two fundamental abstractions are moving point and moving region, describing objects for which only the time-dependent position, or position and extent, are of interest, respectively. We propose to represent such time-dependent geometries as attribute data types with suitable operations, that is, to provide an abstract data type extension to a DBMS data model and query language. This paper presents a design of such a system of abstract data types. It turns out that besides the main types of interest, moving point and moving region, a relatively large number of auxiliary data types is needed. For example, one needs a line type to represent the projection of a moving point into the plane, or a "moving real" to represent the time-dependent distance of two moving points. It then becomes crucial to achieve (i) orthogonality in the design of the type system, i.e., type constructors can be applied uniformly, (ii) genericity and consistency of operations, i.e., operations range over as many types as possible and behave consistently, and (iii) closure and consistency between structure and operations of non-temporal and related temporal types. Satisfying these goals leads to a simple and expressive system of abstract data types that may be integrated into a query language to yield apowerful language for querying spatio-temporal data, including moving objects. The paper formally defines the types and operations, offers detailed insight into the considerations that went into the design, and exempli es the use of the abstract data types using SQL. The paper o ers a precise and conceptually clean foundation for implementing a spatio-temporal DBMS extension.

In this article we describe the data model of the MBase system, a webbased,

Introduction From an object-oriented point of view, software systems are considered to be dynamic collections of autonomous objects that interact with each other. Autonomy means that each object encapsulates all features needed to act as an independent computing agent: individual attributes (data), methods (operations) , behavior (process), and communication facilities. And each object has a unique identity that is immutable throughout lifetime. Coincidentally, objectorientation comes with an elaborate system of classes and types, facilitating structuring and reuse of software. The object approach is widely accepted in software technology, and there are object-oriented programming languages, database systems, and software development methods. The basic idea is not new, because essential features were already present in the programming language Simula [DMN67]. Wider acceptance came with Smalltalk [KG76, GR83]. While the object approach is success

ion Ladder: Combining Algebras - From Functional Pieces to a Whole Andrew U. Frank Department of Geoinformation Technical University Vienna Gusshausstr. 27-29, A-1040 Vienna, Austria frank@geoinfo,tuwien.ac.at Abstract. A fundamental scientific question today is how to construct complex systems from simple parts. Science today seems mostly to analyze limited pieces of the puzzle; the combination of these pieces to form a whole is left for later or others. The lack of efficient methods to deal with the combination problem is likely the main reason. How to combine individual results is a dominant question in cognitive science or geography, where phenomena are studied from individuals and at different scales, but the results cannot be brought together. This paper proposes to use parameterized algebras much the same way that we use functional abstraction (procedures in programming languages) to create abstract building blocks which can be combined later. Algebras group oper...

Shannon and Weaver published 1949 a breakthrough book on how to measure the information transferred over a channel. They introduced the unit `bit' as a measurement unit for information, which stands for one binary decision. This method is commonplace today and widely used to measure amounts of data capacity for storage devices, etc. This does, however, not assess the pragmatic information content of a message. Two messages of very different data and size may communicate the same message and have therefore the same information content; we will call this the pragmatic semantics. We also know that the same message may have very different information content for different users. A theory for a measure of pragmatic information content must account for the fact that different messages may have the same content and that the same message may have different content for different recipients. The prototypical situation is when a recipient of a message uses the information to make a decision about an action. Other situations, where information is assimilated for later usage require some slight extension of the method, but always, information is only useful pragmatically when it influences a decision. To determine information content, the user is modeled as an algebra. All messages which lead to the same actions have the same information content, which is the minimum to determine the action. If two users differ in the action they consider, their algebras differ and therefore the information they deduce from the information content of the same message is different. Both cases are formalized in this paper with algebraic tools. 1

Information systems are open, reactive, and often distributed systems that maintain persistent data. The Troll and omTroll languages aim at specifying information systems on a high level of abstraction, supported by tools integrated in the Tbench. The development is rooted in abstract data types, conceptual modeling, behavior modeling, specification of reactive systems, and concurrency theory.

Jackal is a fine-grained distributed shared memory implementation of the Java programming language. It aims to implement Java’s memory model and allows multithreaded Java programs to run unmodified on a distributed memory system. It employs a multiple-writer cache coherence protocol. In this paper, we report on our analysis of this protocol. We present its formal specification in µCRL, and discuss the abstractions that were made to avoid state explosion. Requirements were formulated and model checked with respect to several configurations. Our analysis revealed two errors in the implementation. Key words: formal specification, model checking, cache coherence protocols, Java memory model, µCRL

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In this paper we use techniques for monad compositions in order to provide a basis for categorical unification in the framework of generalised terms. In particular, we provide results for many-valued sets of terms, and show that this composition of set functors can be extended to a monad.

The OpenMath framework for transmitting mathematical objects over the Internet relies on the concept of Content Dictionaries (CDs) to define the semantics of mathematical objects. This is an essential measure for establishing a meaningful communication amongst mathematical software systems (and humans). Currently, the infrastructure for conceiving, administering, viewing CDs is limited to a file-based almost flat repository. In this paper, we propose to use the OMDoc extension of the OpenMath Xml encoding as an infrastructure to express and manipulate content dictionary information. OMDoc extends OpenMath by adding support for document markup (making the CDs more readable to the human user) and structured specification (making them more explicit, formal, and allow the user to reuse, and inherit CD information in a flexible, but well-defined way).