Fangkai Yang

BWIBots: A platform for bridging the gap between AI and human–robot interaction research

Recent progress in both AI and robotics have enabled the development of general purpose robot platforms that are capable of executing a wide variety of complex, temporally extended service tasks in open environments. This article introduces a novel, custom-designed multi-robot platform for research on AI, robotics, and especially human–robot interaction for service robots. Called BWIBots, the robots were designed as a part of the Building-Wide Intelligence (BWI) project at the University of Texas at Austin. The article begins with a description of, and justification for, the hardware and software design decisions underlying the BWIBots, with the aim of informing the design of such platforms in the future. It then proceeds to present an overview of various research contributions that have enabled the BWIBots to better (a) execute action sequences to complete user requests, (b) efficiently ask questions to resolve user requests, (c) understand human commands given in natural language, and (d) understand human intention from afar. The article concludes with a look forward towards future research opportunities and applications enabled by the BWIBot platform.

Lloyd-Topor Completion and General Stable Models

We investigate the relationship between the generalization of program completion defined in 1984 by Lloyd and Topor and the generalization of the stable model semantics introduced recently by Ferraris et al. The main theorem can be used to characterize, in some cases, the general stable models of a logic program by a first-order formula. The proof uses Truszczynskis stable model semantics of infinitary propositional formulas.

Representing first-order causal theories by logic programs

Nonmonotonic causal logic, introduced by McCain and Turner (McCain, N. and Turner, H. 1997. Causal theories of action and change. In Proceedings of National Conference on Artificial Intelligence (AAAI), Stanford, CA, 460-465) became the basis for the semantics of several expressive action languages. McCains embedding of definite propositional causal theories into logic programming paved the way to the use of answer set solvers for answering queries about actions described in such languages. In this paper we extend this embedding to nondefinite theories and to the first-order causal logic.

Translating first-order causal theories into answer set programming

Nonmonotonic causal logic became a basis for the semantics of several expressive action languages. Norman McCain and Paolo Ferraris showed how to embed propositional causal theories into logic programming, and this work paved the way to the use of answer set solvers for answering queries about actions described in causal logic. In this paper we generalize these embeddings to first-order causal logic--a system that has been used to simplify the semantics of variables in action descriptions.

Relational theories with null values and non-herbrand stable models

Generalized relational theories with null values in the sense of Reiter are first-order theories that provide a semantics for relational databases with incomplete information. In this paper we show that any such theory can be turned into an equivalent logic program, so that models of the theory can be generated using computational methods of answer set programming. As a step towards this goal, we develop a general method for calculating stable models under the domain closure assumption but without the unique name assumption.

Vladimir lifschitz -- a youth at 65

My first meeting with Vladimir was somewhat accidental. What prompted the meeting was that I was assigned by the computer science department at University of Texas at Austin to work as his teaching assistant for the graduate course he was teaching on Mathematical Logic. When we met for the first time in his office, he explained what he was planning to cover during the semester, gave me the book that he was planning to teach from and asked me to sit in on the course so that I would know what he was teaching each week. I agreed to sit in on the course, but without much enthusiasm because I believed that I already knew the content he was planning to teach.