Agent Assistance: From Problem Solving to Music Teaching

We report on our research on agents that act and behave in a web learning environment. This research is part of a general approach to agents acting and behaving in virtual environments where they are involved in providing information, performing transactions, demonstrating products and, more generally, assisting users or visitors of the web environment in doing what they want or have been asked to do. While initially we hardly provided our agents with 'teaching knowledge', we now are in the process of making such knowledge explicit, especially in models that take into account that assisting and teaching takes place in a visualized and information-rich environment. Our main (embodied) tutor-agent is called Jacob; it knows about the Towers of Hanoi, a well-known problem that is offered to CS students to learn about recursion. Other agents we are working on assist a visitor in navigating in a virtual world or help the visitor in getting information. We are now designing a music teacher - using knowledge of software engineering and how to design multi-modal interactions, from previous projects

Structure preserving transformations on non-left-recursive grammars

We will be concerned with grammar covers, The first part of this paper presents a general framework for covers. The second part introduces a transformation from nonleft-recursive grammars to grammars in Greibach normal form. An investigation of the structure preserving properties of this transformation, which serves also as an illustration of our framework for covers, is presented

On the relationship between the LL(k) and LR(k) grammars

In the literature various proofs of the inclusion of the class of LL(k) grammars into the class of LR(k) grammars can be found. Some of these proofs are not correct, others are informal, semi-formal or contain flaws. Some of them are correct but the proof is less straightforward than demonstrated here

Towards Multi-Modal Interactions in Virtual Environments: A Case Study

We present research on visualization and interaction in a realistic model of an existing theatre. This existing ‘Muziek¬centrum’ offers its visitors information about performances by means of a yearly brochure. In addition, it is possible to get information at an information desk in the theatre (during office hours), to get information by phone (by talking to a human or by using IVR). The database of the theater holds the information that is available at the beginning of the ‘theatre season’. Our aim is to make this information more accessible by using multi-modal accessible multi-media web pages. A more general aim is to do research in the area of web-based services, in particu¬lar interactions in virtual environments

Gulliver project: performers and visitors

This paper discusses two projects in our research environment. The Gulliver project, an ambitious project conceived by some artists connected to our research efforts, and the Aveiro-project, as well ambitious, but with goals that can be achieved beause of technological developments, rather than be dependent on artistic and 'political' (read: financial) sources. Both projects are on virtual and augmented reality. The main goal is to design inhabited environments, where 'inhabited' refers to autonomous agents and agents that represent humans, realtime or off-line, visiting the virtual environment and interacting with other agents. The Gulliver environment has been designed by two artists: Matjaz Stuk and Alena Hudcovicova. The Aveiro project is a research effort of a group of researchers trying to design models of intelligence and interaction underlying the behavior of (groups of) agents inhabiting virtual worlds. In this paper we survey the current state of both projects and we discuss current and future attempts to have music performances by virtual and real performers in these environments

Agent-supported cooperative learning environments

We survey our research on (3D) virtual environments inhabited by agents that help visitors to get information and to get a tusk done. The main ideas and designs can be tuned to different applications, including information und transaction services (e-commerce), collaborative work and educational domains

On the covering of left recursive grammars

In this paper we show that some prevailing ideas on the elimination of left recursion in a context-free grammar are not valid. An algorithm and a proof are given to show that every proper context-free grammar is covered by a non-left-recursive grammar

From left-regular to Greibach normal form grammars

Each context-free grammar can be transformed to a context-free grammar in Greibach normal form, that is, a context-free grammar where each right-hand side of a prorfuction begins with a terminal symbol and the remainder of the right-hand side consists of nonterminal symbols. In this short paper we show that for a left-regular grammar G we can obtain a right-regular grammar G’ (which is by definition in Greibach normal form) which left-to-right covers G (in this case left parses of G’ can be mapped by a homomorphism on right parses of G. Moreover, it is possible to obtain a context-free grammar G” in Greibach normal form which right covers the left-regular grammar G (in this case right parses of G” are mapped on right parses of G)

Cover results and normal forms

The purpose of this paper was to sketch an area of problems for the concept of cover. We showed that in spite of some remarks in the literature the problem of covering (unambiguous and -free) cfg's with cfg's in GNF is open. Moreover we gave some properties of covers and we showed a relation between covers and parsability