KR

Knowledge Representation

Hybris-A1: Verification of Non-Terminating Action Programs

The action language GOLOG has been used, among other things, for the specification of the behaviour of mobile robots. Since the task of such autonomous systems is typically open-ended, their GOLOG programs are usually non-terminating. To ensure that the program will let the robot exhibit the intended behaviour, it is often desirable to be able to formally specify and then verify the desired properties, which are often of a temporal nature. This task has been studied within our preliminary work from two perspectives: On the one hand, the problem was tackled for very expressive specification and action program formalisms, but without the goal of achieving decidability, i.e. the developed verification methods were not guaranteed to terminate. On the other hand, the verification problem was studied for action formalisms based on decidable description logics and very limited means of specifying admissible sequences of actions, which allowed us to show decidability and complexity results for the verification problem. The purpose of this project is to combine the advantages of both approaches by, on one hand, developing verification methods for GOLOG programs that are effective and practically feasible and, on the other hand, going beyond the formalisms with very limited expressiveness to enhance their usefulness. Among other things, both qualitative and quantitative temporal program properties will be addressed.

Homepage: http://www.hybrid-reasoning.org/projects/a1

Submitted by Jens Claßen on 1. February 2013 - 19:00 categories [ ]

Seminar Forgetting and Relevance

In this seminar we will study concepts of forgetting and relevance developed in the field of Knowledge Representation. Humans not only forget unintentionally but also intentionally, for example, when they obtain new information and delete previous contradicting and apparently false information. In fact, humans usually do not forget irrevocably; we can bring back memories and reconstruct forgotten knowledge. In formal languages as studied in KR, however, even supposedly simple forgetting often turns out very difficult. In this seminar, we will study techniques for forgetting in KR languages such as predicate logic, description logics, or answer set programs. Related to forgetting is the concept of relevance among different facts. For example, when some fact is to be forgotten, this may also affect other facts relevant to the forgotten fact. Relevance is useful to develop tractable reasoning and handling inconsistencies in a knowledge base.

Submitted by Christoph Schwering on 30. December 2015 - 20:59 categories [ ]

Seminar Beliefs and Causality

In this seminar we will study papers from various subfields of Knowledge Representation. This includes belief revision; argumentation theory; planning; causality in general and the situation calculus in particular. All of these subfields of AI are related to each other. For example, one usually acts depending on what one believes, and actions in turn affect one's beliefs. In this seminar, we will study recent papers on these topics (particularly from the IJCAI-15 conference).

Submitted by Christoph Schwering on 2. August 2015 - 5:40 categories [ ]

Bachelor's Thesis: Multi-Agent Simulation of the Water Quality in Megacities [assigned]

Description

Humanity has crossed the line from being a rural to urban species since 2007. For the first time in history, more people live in cities and urban areas than in the countryside. Starting in the developed ations, where the urbanisation process has been significantly decelerated in the meantime, urbanisation has especially increased in Asia and South America as well as in Africa to a substantial extent in the second half of the last century. Processes of urbanisation have a negative influence on the availability and quality of water resources. Especially in developing and emerging countries, the hydrological and hydrogeological setting of each region is deteriorated through the growing urbanization processes. Often the hydrological and hydrogeological basis of an area is strongly affected by rocesses of urbanisation in these countries. Changes of the structure of urban development going along with the urbanisation will not be without consequences for the environment and water resources.

In frame of this background the Department of Engineering Geology and Hydrogeology of the RWTH Aachen University analysis the interaction between high speed urbanisation/mega-urbanisation and water resources in China and India. In context to this we want to develop a knowledge-based planning and simulation framework.

Submitted by Martin Liebenberg on 12. January 2015 - 18:33 categories [ ]

Lecture - Introduction to Knowledge Representation SS 2015

An announcement of the course can also be found in the course information system CAMPUS.

Submitted by Jens Claßen on 12. January 2015 - 11:57 categories [ ]

Bachelor's Thesis: Efficient Default Reasoning in Golog with Answer Set Programming [completed]

The goal of this thesis was to integrate Answer Set Programming (ASP) into a Golog system in order to obtain an agent framework that is capable of efficient non-monotonic reasoning with introspection.

Submitted by Jens Claßen on 16. December 2014 - 19:00 categories [ ]

Seminar Dynamics of Knowledge and Belief

In this seminar we will study several modeling and reasoning techniques for knowledge and belief in dynamic systems. Knowledge is an important aspect of intelligent programs: while most of today's systems assume a closed world, i.e., everything they don't know to be true is assumed to be false, an intelligent system needs to consider possible that there are truths not known to the system. In a dynamic environment, i.e., an environment where one or multiple agents (inter)act, the system will usually have to acquire new knowledge through sensing. Potentially it may even revise its beliefs when it realizes some beliefs were wrong. In this seminar we will study various aspects of action, knowledge, and belief.

We plan to implement a peer review process for this seminar. That is, every student will read some other students' term paper and provide feedback in form of a written review. This shall not only deepen your understanding of the other topics, but it also introduces you to the academic review process.

Submitted by Christoph Schwering on 6. January 2014 - 0:08 categories [ ]

Diploma Thesis: Towards Decidable Verification of Non-Terminating Golog Programs [completed]

Claßen and Lakemeyer recently introduced algorithms for the verification of temporal properties of non-terminating Golog programs, based on the first-order modal Situation Calculus variant ES, and regression-based reasoning. However, while Golog’s high expressiveness is a desirable feature, it also means that their verification procedures cannot be guaranteed to terminate in general. In this thesis, we address this problem by showing that, for a relevant subset, the verification of non-terminating Golog programs is indeed decidable, which is achieved by means of three restrictions. First, we use the ES variant of a decidable two-variable fragment of the Situation Calculus that was introduced by Gu and Soutchanski. Second, we have to restrict the Golog program to contain ground action only. Finally, we consider special classes of successor state axioms, namely the context-free ones and those that only admit local effects.

Submitted by Martin Liebenberg on 13. April 2013 - 19:45 categories [ ]

Lecture - Introduction to Knowledge Representation SS 2013

An announcement of the course can also be found in the course information system CAMPUS.

Submitted by Jens Claßen on 1. February 2013 - 16:05 categories [ ]

Lecture - Introduction to Knowledge Representation

An announcement of the course can also be found in the course information system CAMPUS.

Submitted by Daniel Beck on 3. April 2012 - 11:29 categories [ ]