Hele-Mai Haav

Databases and Information Systems II

Due to the increasing demand to provide data from databases for servicing web-based applications and the de facto distribution of data on the web the problem arises to generalize database distribution t.echniques from relational to object oriented and semi-structured data. The major difference between these two is that object orientation refers to a predefined schema, whereas semi-structured data is meant to be schema-Iess. The paper generalizes horizontal and vertical fragmentation first to an object oriented datamodel, then to semi-structured data and XML. In this context, the paper discusses the problem of preservation of unique object identifiability with respect to fragmentation. Furthermore, splitting will be introduced as a a third kind of fragmentation.

Semi-automated Generation of DSL Meta Models from Formal Domain Ontologies

This paper addresses the problem of alignment of domain ontologies and meta-models of Domain Specific Languages DSL in order to facilitate the DSL development process by formal methods. The solution presented in this paper automatically generates design templates of a DSL meta-model that are consistent with a given domain ontology represented in OWL DL. Consistency of alignment is ensured by predefined mapping rules between constructs of ontology modelling language OWL DL and a modelling language used for representing DSL meta-models. The approach is implemented as an extension to the CoCoViLa system and the CoCoViLa modelling language is used for representing DSL meta-models. The evaluation of the provided method is carried out by developing the DSL for the IT risk analysis and management domain.

Approaches to Concept Based Exploration of Information Resources

This paper discusses methods for improving the usual keyword based retrieval from information resources. Common to these methods is the use of lattices to structure the conceptual content of the information resources. The first method discussed relies on construction of ontology by a human being acquainted with a considered knowledge domain. The second approach constructs a formal concept lattice by algorithmic analysis of keyword patterns in the text.

A Practical Methodology for Development of a Network of e-Government Domain Ontologies

Ontologies are widely proposed for solving semantic interoperability problems in e-government domain. However, less attention is paid on methodological issues of ontology development in this domain. These are not sufficiently solved. Existing approaches in ontology development are technically very demanding and require long learning curve and are therefore inefficient for this purpose. E-government domain ontologies could be efficiently developed by domain experts rather than ontology engineers. The paper proposes a novel ontology development methodology for construction of light-weight domain ontologies by bringing ontology modeling closer to domain experts that are actual domain knowledge holders. The approach is illustrated and evaluated by development of a network of e-government domain ontologies used for achieving semantic interoperability of state information systems (IS) in Estonia.

Learning Ontologies for Domain-Specific Information Retrieval

Ontologies are used in information retrieval in order to improve traditional document search methods like keyword-based search or browsing hierarchies of subject categories on the Web. To make it possible to use ontologies for that purpose requires fast automatic or semi-automatic building of formal ontologies that can be processed by a computer. This paper describes a new approach to the automatic discovery of domain-specific ontologies in order to make it possible by intelligent agents to better “understand” the intended meaning of descriptions of objects to be retrieved from different web catalogues. The approach is based on automatic construction of domain-specific ontologies using Natural Language Processing (NLP) and Formal Concept Analysis (FCA). Besides the general framework of the approach, a principal architecture of a prototypical ontology design tool OntoDesign is presented. OntoDesign is a system for automatic construction of formal domain ontologies from given domain-specific texts by using FCA.

A Deductive Object-Oriented Approach to Information System Modeling

In this paper we propose an approach to modeling dynamics and declarativeness in information systems (IS) by using general rules. The approach is based on object-oriented and logic languages co-operatively working within IS environment. The communication between the languages is organized by means of transformations from one language to another. We also consider methods for optimization of the co-operative work. A set of transformations, the usage of some general rules for problem solving and optimization technique based on partial deduction are presented and illustrated by means of examples.

Ontology-Based Integration of Software Artefacts for DSL Development

This paper addresses a high level semantic integration of software artefacts for the development of Domain Specific Languages (DSL). The solution presented in the paper utilizes a concept of DSL meta-model ontology that is defined in the paper as consisting of a system ontology linked to one or more domain ontologies. It enables dynamic semantic integration of software artefacts for the composition of a DSL meta-model. The approach is prototypically implemented in Java as an extension to the DSL development tool CoCoViLa.

A rule-based approach to Web-based application development

Common design patterns in application development mix implementation of business logic with application logic, user interface logic, or with data access logic. This leads to results that business logic is not well maintainable and reusable, the application code should be reimplemented each time the business logic has changed or the same business logic should be reimplemented for each application. This paper presents a new rule-based approach to Web-based IS development making possible separating the business logic from interface or application logic when creating complex Web-based software applications. The technology consists of 2 main parts: the application server Xstone for creating 3-layered systems and the RqlGandalf rule solver. The middleware server Xstone connects to Oracle, PostgreSQL databases and the Rql rule system. The Rql rule system is targeted for defining and using business logic rules. The Rql rule system is able to read data from a SQL database: it can call the application server and import/convert SQL-given data into its own knowledge base. The presented rule-based system development technology is implemented for the Linux platform as open source software

Specifying Semantics of Evolution in Object-Oriented Databases Using Partial Deduction

In this paper, we propose a methodology for specification of semantics of evolution in object-oriented databases. Our methodology is based on Horn logic as metalanguage for specification of semantics of both schema and object evolution in object-oriented databases. Partial Deduction is used as technique for specialization of a set of general constraints on database and its schema and to derive conditions that must be satisfied to guarantee the validity of managing evolution in object-oriented databases. Implementation principles of the methodology are discussed on the basis of the object-oriented language NUT. Different types of transformations are defined that allow derivation of predicates from the descriptions of classes and objects used in the NUT system.

Domain Ontology for Expressing Knowledge of Variants of Thermally Modified Wood Products

The thermally modified wood producer Thermory AS manufactures about 400 different products, which are ordered in large number of variants that makes the expression of the product variant knowledge and its validation very important. In this paper, we express knowledge of product variants as domain ontology in order to capture the product knowledge in the way that is consistent and shareable between humans and machines. Using Ontology Web Language (OWL) as Description Logics (DL) based ontology representation language enables to detect inconsistency in the product knowledge and customer order requirements. Constraints on valid product variants are expressed as OWL class expressions and as rules in Semantic Web Rule Language (SWRL). The provided knowledge representation method makes it possible to reduce combinatorial complexity of description of product variants and to place correct manufacturing orders saving time and money for the company.