Mads Nygård

Different roles and mutual dependencies of data, information, and knowledge—an AI perspective on their integration

The unclear distinction between data, information, and knowledge has impaired their combination and utilization for the development of integrated systems. There is need for a unified definitional model of data, information, and knowledge based on their roles in computational and cognitive information processing. An attempt to clarify these basic notions is made, and a conceptual framework for integration is suggested by focusing on their different roles and frames of reference within a decision-making process. On this basis, ways of integrating the functionalities of databases, information systems and knowledge-based systems are discussed by taking a knowledge level perspective to the analysis and modeling of systems behaviour. Motivated by recent work in the area of case-based reasoning related to decision support systems, it is further shown that a specific problem solving episode, or case, may be viewed as data, information, or knowledge, depending on its role in decision making and learning from experience. An outline of a case-based system architecture is presented, and used to show that a focus on the retaining and reuse of past cases facilitates a gradual and evolutionary transition from an information system to a knowledge-based system.

An Advanced Discrete Model for Uncertain Spatial Data

This paper presents a discrete model for storing uncertain spatial data in a database. It expands on earlier works on modelling uncertain and vague regions as well as an abstract model of uncertain spatial data developed by the present authors. The model presented in this paper is based on a vector representation of the spatial data and covers uncertain points, uncertain lines and uncertain regions as well as uncertain versions of base types such as integers. Three alternative methods for computing the probabilities associated with uncertain spatial data are included. This paper also describes how to implement two operations with these types.

Representing topological relationships for spatiotemporal objects

Several representations have been created to store topological information in normal spatial databases. Some work has also been done to represent topology for 3D objects, and such representations could be used to store topology for spatiotemporal objects. However, using 3D models has some disadvantages with regards to retrieving snapshots of the database. This paper aims at creating a spatiotemporal version of the sliced representation that supports efficient retrieval of snapshots of the past and that supports enforcing topological relationships. This paper aims to extend an earlier representation of moving objects so that it can also store and enforce some of the topological relationships between the objects. One use of such a representation is storing a changing spatial partition. As part of the effort to construct the model, an analysis of the topological relationships has been carried out to see which need to be stored explicitly and which can be computed from geometry. Both a basic time slice model and a 3D model are examined to determine how suitable they are for storing topological relationships. An extension of the time slice model is then proposed that solves some of the problems of the basic time slice model. Some algorithms for constructing the new model from snapshots of the objects along with an adjacency graph have been created. The paper also contains a short analysis on how to handle current time, as the time slice model is best at handling historical data, and on ways to speed up searches in a database in which objects of many types are connected to one another and many files therefore potentially need to be accessed.

CAGISTrans: Providing Adaptable Transactional Support for Cooperative Work – an Extended Treatment

The theme of this paper is on transactional support for cooperative work environments, focusing on data sharing – i.e., providing suitable mechanisms to manage concurrent access to shared resources. The subject is not new per se. In fact, in terms of transaction models and frameworks, several solutions already exist. Still, there are some problems that are not solved. Among these are the problems that result from the dynamic and heterogeneous nature of cooperative work. Our solution is to provide transactional support that not only can be tailored to suit different situations, but can also be modified following changes in the actual environment while the work is being performed – i.e., adaptable transactional support. As part of this, we have identified and extracted the beneficial features from existing models and attempted to extend these to form a transactional framework, called CAGISTrans. This is a framework for the specification of transaction models suiting specific applications. To handle dynamic environments we propose a new way of organizing the elements of a transaction model to allow runtime refinement. In addition, we have developed a transaction management system, built on the middleware principle, to allow interoperability and database independence. Thus this addresses the problems induced by the heterogeneous nature of cooperative environments.

A medium complexity discrete model for uncertain spatial data

This paper presents a method for representing uncertainty in spatial data in a database. The model presented requires moderate amounts of storage space. To compute the probability that an object is at a particular place, the representation employs probability functions that can be computed quickly and efficiently. This is different from an advanced model presented by the same authors. This medium complexity model is less powerful, but requires much less storage space, and computing probabilities is much less complicated.

A Discrete Model for Topological Relationships between Uncertain Spatial Objects

Even though the positions of objects may be uncertain, one may know some topological information about them. In this paper, we develop a new model for storing topological relationships in uncertain spatial data. It is intended to be the equivalent of such representations as the Node-Arc-Area representation but for spatial objects with uncertain positions.

Abstract and discrete models for uncertain spatiotemporal data

Summary form only given. We deal with the uncertainty in spatial and spatiotemporal databases. Due to lack of accurate measurements, or rapid changes in time, spatial and spatiotemporal data are often uncertain. Our work presents new abstract and discrete models for uncertain spatial and spatiotemporal information. The models are based on the principle that one knows that the uncertain object, regardless of type, must be within a certain area.

A transaction model for supporting mobile collaborative works

This paper presents a mobile transaction model for supporting mobile collaborative works. The mobile transaction processing system supports data sharing among mobile hosts via the concept of mobile affiliation workgroups. Data sharing among mobile transactions in a mobile affiliation workgroup is supported by export and import transactions in an export-import repository, which is a mobile sharing workspace. This means that the data sharing process is divided into smaller transaction processes and separated from the main transactions. The mobile transaction system also distinguishes two different mechanisms for supporting data sharing in mobile environments, which are sharing data states and sharing data status.

Quality Requirements of Migration Metadata in Long-Term Digital Preservation Systems

Migration is the most common preservation strategy in long-term digital preservation systems. It relays old digital objects from one technique to another. A prerequisite for a successful migration is the availability of migration metadata, which provide enough background information to preserved digital objects. Without the migration metadata, the migration may not be possible, but also the digital object’s consistency may be violated. It is therefore recognized that the migration metadata are essential but surprisingly no requirements on these migration metadata seem to be available. In this paper, quality requirements of such migration metadata are derived from common preservation metadata schemas. The completeness and the usefulness of these quality requirements are validated by a case study. The final results show that the quality requirements can actually improve the workflow of a migration procedure. In addition, they can be used to improve metadata schemas and thereby decrease the risks in future migrations. Finally, six improvement suggestions for preservation systems are derived from our analysis of the quality requirements.

Cooperative database system: a constructive review of cooperative transaction models

The use of transactions to provide reliable and secure information processing and data management has increasingly gained the attention of the CSCW community. Traditional transaction models have, however been claimed to be too restrictive in the context of cooperation. Research on transaction support for cooperative work has therefore particularly aimed at finding mechanisms and frameworks to overcome this limitation. In this paper we survey the work done in the development of flexible and cooperative transaction models. This survey has been divided into two categories. The first consists of approaches mainly based on the CSCW perspective, while the second category consists of database methods extended to support cooperation. The paper also provides an evaluation of the models with respect to relevant criteria and requirements for cooperative work settings.