Viljan Mahnic

Converting metamodels to graph grammars: doing without advanced graph grammar features

In this paper, we present a method to convert a metamodel in the form of a UML class diagram into a context-sensitive graph grammar whose language comprises precisely the set of model graphs (UML object diagrams) that conform to the input metamodel. Compared to other approaches that deal with the same problem, we use a graph grammar formalism that does not employ any advanced graph grammar features, such as application conditions, precedence rules, and production schemes. Specifically, we use Rekers and Schürr’s Layered Graph Grammars, which may be regarded as a pure generalization of standard context-sensitive string grammars. We show that elementary grammatical features, i.e., grammar labels and context-sensitive graph rewrite rules, suffice to represent metamodels with arbitrary multiplicities and inheritance. Inspired by attribute string grammars, we also propose a graph-grammar-based approach to the semantic analysis of model graphs.

Separation of Interleaved Web Sessions with Heuristic Search

We describe a heuristic search-based method for interleaved HTTP (Web) session reconstruction building upon first order Markov models. An interleaved session is generated by a user who is concurrently browsing the same web site in two or more web sessions (browser tabs or windows). In order to assure data quality for subsequent phases in analyzing users browsing behavior, such sessions need to be separated in advance. We propose a separating process based on best-first search and trained first order Markov chains. We develop a testing method based on various measures of reconstructed sessions similarity to original ones. We evaluate the developed method on two real world click stream data sources: a web shop and a university student records information system. Preliminary results show that the proposed method performs well.

Improving the graph grammar parser of Rekers and Schurr

Graph grammars and graph grammar parsers are to visual languages what string grammars and parsers are to textual languages. A graph grammar specifies a set of valid graphs and can thus be used to formalise the syntax of a visual language. A graph grammar parser is a tool for recognising valid programs in such a formally defined visual language. A parser for context-sensitive graph grammars, which have proved to be suitable for formalising real-world visual languages, was developed by Rekers and Schurr. We propose three improvements of this parser. One of them enlarges the class of parsable graph grammars, while the other two increase the parsers computational efficiency. Experimental results show that for some (meaningful) graph grammars, our improvements can enhance the parsers performance by orders of magnitude. The proposed improvements will hopefully increase both the parsers applicability and the interest in visual language parsing in general.

Teaching Scrum in Cooperation with a Software Development Company

Teaching Scrum in Cooperation with a Software Development Company The increasing use of agile methods for software development creates the need for these methods to become part of the education of future computer and information science engineers. On the other hand, teaching these methods gives us an opportunity to verify individual agile concepts and their effectiveness. For that reason, project work is an appropriate and frequently used form of teaching that enables students to get acquainted with agile methods and, at the same time, provides case studies for evaluating individual agile concepts. We describe our approach to teaching the Scrum agile method, within the software technology course, in cooperation with a software development company. Students were taught through work on a real project for which a list of requirements was submitted by the company. A co-worker of this company participated throughout the teaching period playing the role of customers representative. During their work, students consistently used the Scrum method and at the end of each iteration they evaluated their experience by means of a questionnaire. In the article, the Scrum method is presented first, then a description of work on the project is given and finally the results of the survey are described.

Data Quality: A Prerequisite for Succesful Data Warehouse Implementation

1. The University of Ljubljana is the largest university in Slovenia. It consists of 26 member institutions (20 faculties, 3 academies, and 3 colleges) and has more than 40,000 students. In the past, the member institutions had substantial autonomy regarding the usage of information technologies, which led to uncoordinated development of their information systems. Different applications were developed for the same purpose and due to this heterogeneity it is very difficult or even impossible to create reports that require cross-referencing data from different institutions or application areas.

TEACHING INFORMATION SYSTEM TECHNOLOGY IN PARTNERSHIP WITH IT COMPANIES

Teaching Information System Technology in Partnership with IT Companies We describe an example of partnership between a university and some major IT companies - IBM and Microsoft - to teach a course on information systems technology. The course is taught in the fifth (final) year of the university undergraduate program when students have already mastered the basic theoretical knowledge of information system development. For this reason, the course content was restructured to pay more attention to practical experience and the learning opportunities available within the environment of professional industry. During the course, students get acquainted with IBM and Microsoft products and the tools that support the development of online information systems. Special attention is devoted to group project work, which is not just intended for the improvement of technical skills, but also for the aqusition of transferrable skills such as teamwork, management/leadership, planning and organizing, presentation and documentation, searching for information, etc. We describe our experience from teaching the course in the academic years 2005/06 and 2006/07. A description of the course content is given and the results of a survey among the students are presented. Students responded favourably to the new approach and found the course very useful and interesting.

Portal Technology for Integrated, User-Centric University Information Systems

The paper describes a project that was launched as the first step towards the realisation of the Information Systems (IS) strategy plan developed for the University of Ljubljana. The strategy plan revealed many weaknesses and disadvantages of the current university IS. One of them was the lack of the possibility to utilize e-business technology. As a response the University of Ljubljana decided to renovate the current Student records IS using a technology which seems to be very promising in developing integrated, usercentric IT solutions. In the paper, we shortly introduce the strategy plan and discuss some characteristics of the portal technology. In more detail we focus on the renovation of the Student records IS. In conclusion, we expose some difficulties that we had to deal with during the project.