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Daniel Eckert, Christian Klamler Institute of Public Economics University of Graz  TU VIENNA, Seminarroom Goedel (Favoritenstrasse 911, ground floor, access through courtyard)  Fri, 13. Apr 01, 9:00 
SOCIAL CHOICE  Problems, results, tools and recent extensions  
The aim of this tutorial is to give an introduction into social choice theory with special emphasis on tools of general relevance developed in this area (as extensions of rankings of objects to sets and distancebased approaches) and recent extensions (e.g. judgment aggregation).  

Daniel Eckert, Christian Klamler Institute of Public Economics University of Graz  TU VIENNA, Seminarroom Goedel (Favoritenstrasse 911, ground floor, access through courtyard)  Fri, 13. Apr 01, 9:00 
SOCIAL CHOICE  Problems, results, tools and recent extensions  
The aim of this tutorial is to give an introduction into social choice theory with special emphasis on tools of general relevance developed in this area (as extensions of rankings of objects to sets and distancebased approaches) and recent extensions (e.g. judgment aggregation).  

Hermann Miki  Vienna University of Technology, Seminarroom "Gödel", Favoritenstr. 9, access from the inner courtyard  Wed, 28. Apr 10, 17:00 
"How to Assign Papers to Referees"  
The problem to assign papers to referees gained a considerable interest in the recent years, especially in the scope of conference management systems. These systems need to achieve a fair and balanced distribution of papers among referees, where the conditions of fairness and balance may be defined in several ways. We present two algorithms to distribute a possibly large number of papers among a smaller number of referees, each paper requiring k reports. The first one is an approximation algorithm, using an iteration of weighted maximum matching in bipartite graphs. The second one is an exact algorithm based on bmatching. The optimality criterion for the assignment is not based on a local view of each referee, but on a global performance of the whole kassignment satisfying a fairness criterion. We introduce an objective function for the kassignment problem ensuring a specific notion of fairness when it is maximized. We show how a few precisely defined fairness criteria can be achieved that way. This includes a particularly notable extension of rankmaximality, a notion ntroduced by Irving et al. Our second algorithm computes in polynomial time optimal kassignments with respect to the aforementioned fairness function.  

Wang Qing  TU Vienna, Seminarroom Goedel, Favoritenstr. 911, ground floor (access through inner courtyard)  Fri, 23. Jul 10, 11:00 
A Logic for NonDeterministic Database Transformations  
Database transformations provide a unifying view for queries and updates, the two fundamental types of computations in any databases capturing the capability to retrieve and update data. The integration of queries and updates has always been a research challenge in database theory. The emerging new application areas such as webbased systems and serviceoriented architectures have further increased the importance of this problem. Recently, it was shown that nondeterministic database transformations can be captured exactly by a variant of Abstract State Machines (ASMs), the socalled Database Abstract State Machines (DBASMs). In this talk I will present a logic for DBASMs. in spite of bounded nondeterminism permitted by DBASMs, the logic for DBASMs is proven to be sound and complete when the logic of meatfinite states is parameterised by the firstorder logic. This is due to the finiteness condition stipulated on the database part of a state of database transformations, which thereby leads to the finiteness of update sets and multisets in onestep transitions. We can then formalise nondeterminism of DBASMs by utilising a modal operator [] for an update set of multiset generated by a DBASM rule. The logic for DBASMs lies down a solid foundation for developing verification techniques to study the properties of database transformations in various dataintensive applications.  

Paul Dunne  TU Wien,, Seminarraum Gödel, Favoritenstraße 911, Erdgeschoß, 1040 Wien  Thu, 12. Apr 12, 12:00 
Mixed Argumentation Frameworks  
We introduce a derivative of Dung's seminal abstract argumentation frameworks (AFs) through which distinctive features both of Dung's semantics and socalled ``valuebased'' argumentation frameworks (VAFs) may be captured. These frameworks, which we describe as mixed AFs, thereby recognise that, in some circumstances, arguments may be deemed acceptable, not only as a consequence of subjective viewpoints (as are modelled by the concept of audience in VAFs) but also as a consequence of ``value independent'' acceptance of other arguments: for example in the case of factual statements. We analyse divers acceptability conditions for arguments in mixed AFs. These may be be formulated independently of any specific extensionbased semantics, so that variants considering preferred, semistable, resolutionbased etc are possible. We, further, obtain a complete picture for the computational complexity of the associated decision questions in both preferred and semistable cases. This analysis has two surprising consequences: reasoning in mixed AFs poses significantly greater computational challenges than either standard or valuebased questions, a number of problems being complete at the third level of the polynomialtime hierarchy (as opposed to worstcase secondlevel completeness results in standard AFs). Secondly, mixed credulous reasoning questions are as demanding as mixed sceptical reasoning (in preferred semantics) and, under standard assumptions, can even be harder (in semistable semantics).  

Eckert, Daniel, Klamler Christian, Institute of Public Economics University of Graz  TU VIENNA, Seminarroom Goedel (Favoritenstrasse 911, ground floor, access through courtyard)  Fri, 13. Apr 12, 9:00 
Social Choice  problems, results, tools and recent extensions  
The aim of this tutorial is to give an introduction into social choice theory with special emphasis on tools of general relevance developed in this area (as extensions of rankings of objects to sets and distancebased approaches) and recent extensions (e.g. judgment aggregation).  

Schweikardt Nicole  TU VIENNA, Seminarroom Goedel (Favoritenstrasse 911, ground floor, access through courtyard)  Thu, 9. Aug 12, 11:15 
Querying Graph Structured Data  
Many application areas (e.g., concerning the semantic web or biological applications) consider graph structured data, where the data consists of a finite set of nodes connected by labeled edges. For querying such data one usually needs to specify types of paths along which nodes are connected. A widely studied class of queries for graph structured databases are the conjunctive regular path queries, where types of paths can be described by regular expressions specifying labels along the paths. For modern applications, however, also more expressive query languages are desirable, allowing not only to specify regular properties of path labels, but also to compare paths based on, e.g., their lengths, labels, or similarity. The aim of this talk is to give an overview of recent developments in this area. Special emphasis will be put on query languages, their expressive power, and their complexity concerning query evaluation and static analysis. With kind support of the Wolfgang Pauli Institut (WPI).  

James Delgrande  Seminarroom Gödel (Favoritenstrasse 911, ground floor, access through courtyard  Mon, 5. Nov 12, 16:00 
Revising Horn Theories  
This talk addresses belief revision where the underlying logic is that governing Horn clauses. It proves to be the case that classical (AGM) belief revision doesn't immediately generalise to the Horn case. In particular, a standard construction based on a total preorder over possible worlds may violate the accepted (AGM) postulates. Conversely, Horn revision functions in the obvious extension to the AGM approach are not captured by total preorders over possible worlds. We address these difficulties by first restricting the semantic construction to ``well behaved'' orderings; and second, by augmenting the revision postulates by an additional postulate. This additional postulate is redundant in the AGM approach but not in the Horn case. In a representation result we show that these two approaches coincide. Arguably this work is interesting for several reasons. It extends AGM revision to inferentiallyweaker Horn theories; hence it sheds light on the theoretical underpinnings of belief change, as well as generalising the AGM paradigm. Thus, this work is relevant to revision in areas that employ Horn clauses, such as deductive databases and logic programming, as well as areas in which inference is weaker than classical logic, such as in description logic.  

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