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WELL (AND BETTER) QUASIORDERED TRANSITION SYSTEMS
"... Abstract. In this paper, we give a step by step introduction to the theory of well quasiordered transition systems. The framework combines two concepts, namely (i) transition systems which are monotonic wrt. a wellquasi ordering; and (ii) a scheme for symbolic backward reachability analysis. We de ..."
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Abstract. In this paper, we give a step by step introduction to the theory of well quasiordered transition systems. The framework combines two concepts, namely (i) transition systems which are monotonic wrt. a wellquasi ordering; and (ii) a scheme for symbolic backward reachability analysis. We describe several models with infinitestate spaces, which can be analyzed within the framework, e.g., Petri nets, lossy channel systems, timed automata, timed Petri nets, and multiset rewriting systems. We will also present better quasiordered transition systems which allow the design of efficient symbolic representations of infinite sets of states. §1. Introduction. 1.1. Background. Current capabilities in computer technology allow enormously complicated implementations of such systems, making the task of producing errorfree products more and more difficult. Consequently, it is of great practical and economical importance to develop methods which make the design
Spatiotemporal reasoning about epidemiological data
 Artificial Intelligence in Medicine
, 2006
"... Objective. In this article, we propose new methods to visualize and reason about spatiotemporal epidemiological data. Background. Efficient computerized reasoning about epidemics is important to public health and national security, but it is a difficult task because epidemiological data are usually ..."
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Objective. In this article, we propose new methods to visualize and reason about spatiotemporal epidemiological data. Background. Efficient computerized reasoning about epidemics is important to public health and national security, but it is a difficult task because epidemiological data are usually spatiotemporal, recursive, and fast changing hence hard to handle in traditional relational databases and geographic information systems. Methodology. We describe the general methods of how to (1) store epidemiological data in constraint databases, (2) handle recursive epidemiological definitions, and (3) efficiently reason about epidemiological data based on recursive and nonrecursive SQL queries. Results. We implement a particular epidemiological system called WeNiVIS that enables the visual tracking of and reasoning about the spread of the West Nile Virus epidemic in Pennsylvania. In the system, users can do many interesting reasonings based on the spatiotemporal dataset and the recursively defined risk evaluation function through the SQL query interfaces. Conclusions. In this article, the WeNiVIS system is used to visualize and reason about the spread of West Nile Virus in Pennsylvania as a sample application. Beside this particular case, the general methodology used in the implementation of the system is also appropriate for many other applications. Our general solution for reasoning about epidemics and related spatiotemporal phenomena enables one to solve many problems similar to WNV without much modification. Preprint submitted to International Journal of Artificial Intelligence in Medicine 1
Quantifierelimination for the firstorder theory of boolean algebras with linear cardinality constraints
 In Proc. Advances in Databases and Information Systems (ADBIS’04), volume 3255 of LNCS
, 2004
"... Abstract. We present for the firstorder theory of atomic Boolean algebras of sets with linear cardinality constraints a quantifier elimination algorithm. In the case of atomic Boolean algebras of sets, this is a new generalization of Boole’s wellknown variable elimination method for conjunctions o ..."
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Abstract. We present for the firstorder theory of atomic Boolean algebras of sets with linear cardinality constraints a quantifier elimination algorithm. In the case of atomic Boolean algebras of sets, this is a new generalization of Boole’s wellknown variable elimination method for conjunctions of Boolean equality constraints. We also explain the connection of this new logical result with the evaluation of relational calculus queries on constraint databases that contain Boolean linear cardinality constraints. 1
Temporal Data Classification Using Linear Classifiers. Information Systems (submitted
, 2009
"... Abstract. Data classification is usually based on measurements recorded at the same time. This paper considers temporal data classification where the input is a temporal database that describes measurements over a period of time in history while the predicted class is expected to occur in the futur ..."
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Abstract. Data classification is usually based on measurements recorded at the same time. This paper considers temporal data classification where the input is a temporal database that describes measurements over a period of time in history while the predicted class is expected to occur in the future. We describe a new temporal classification method that improves the accuracy of standard classification methods. The benefits of the method is tested on weather forecasting using the meteorological database from the Texas Commission on Environmental Quality. 1
How Would You Like to Aggregate Your Temporal Data
 In Proceedings of TIME
, 2006
"... Realworld data management applications generally manage temporal data, i.e., they manage multiple states of timevarying data. Many contributions have been made by the research community for how to better model, store, and query temporal data. In particular, several dozen temporal data models and q ..."
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Realworld data management applications generally manage temporal data, i.e., they manage multiple states of timevarying data. Many contributions have been made by the research community for how to better model, store, and query temporal data. In particular, several dozen temporal data models and query languages have been proposed. Motivated in part by the emergence of nontraditional data management applications and the increasing proliferation of temporal data, this paper puts focus on the aggregation of temporal data. In particular, it provides a general framework of temporal aggregation concepts, and it discusses the abilities of five approaches to the design of temporal query languages with respect to temporal aggregation. Rather than providing focused, polished results, the paper’s aim is to explore the inherent support for temporal aggregation in an informal manner that may serve as a foundation for further exploration. 1
Verification of qualitative Z constraints
"... Abstract. We introduce an LTLlike logic with atomic formulae built over a constraint language interpreting variables in Z. The constraint language includes periodicity constraints, comparison constraints of the form x = y and x < y, it is closed under Boolean operations and it admits a restricte ..."
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Abstract. We introduce an LTLlike logic with atomic formulae built over a constraint language interpreting variables in Z. The constraint language includes periodicity constraints, comparison constraints of the form x = y and x < y, it is closed under Boolean operations and it admits a restricted form of existential quantification. This is the largest set of qualitative constraints over Z known so far, shown to admit a decidable LTL extension. Such constraints are those used for instance in calendar formalisms or in abstractions of counter automata by using congruences modulo some power of two. Indeed, various programming languages perform arithmetic operators modulo some integer. We show that the satisfiability and modelchecking problems (with respect to an appropriate class of constraint automata) for this logic are decidable in polynomial space improving significantly known results about its strict fragments. As a byproduct, LTL modelchecking over integral relational automata is proved complete for polynomial space which contrasts with the known undecidability of its CTL counterpart. 1
Reclassification of linearly classified data using constraint databases
 In: Atzeni P, Caplinskas A, Jaakkola H, editors. 12th East European Conference on Advances of Databases and Information Systems
"... Abstract. In many problems the raw data is already classified according to a variety of features using some linear classification algorithm but needs to be reclassified. We introduce a novel reclassification method that creates new classes by combining in a flexible way the existing classes without ..."
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Abstract. In many problems the raw data is already classified according to a variety of features using some linear classification algorithm but needs to be reclassified. We introduce a novel reclassification method that creates new classes by combining in a flexible way the existing classes without requiring access to the raw data. The flexibility is achieved by representing the results of the linear classifications in a linear constraint database and using the full query capabilities of a constraint database system. We implemented this method based on the MLPQ constraint database system. We also tested the method on a data that was already classified using a decision tree algorithm. 1
Logic and computational complexity for Boolean information retrieval
 IEEE Trans. Knowl. Data Eng
, 2006
"... Abstract — We study the complexity of query satisfiability and entailment for the Boolean Information Retrieval models WP and AWP using techniques from propositional logic and computational complexity. WP and AWP can be used to represent and query textual information under the Boolean model using t ..."
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Abstract — We study the complexity of query satisfiability and entailment for the Boolean Information Retrieval models WP and AWP using techniques from propositional logic and computational complexity. WP and AWP can be used to represent and query textual information under the Boolean model using the concept of attribute with values of type text, the concept of word, and word proximity constraints. Variations of WP and AWP are in use in most deployed digital libraries using the Boolean model, text extenders for relational database systems (e.g., Oracle 10g), search engines and P2P systems for information retrieval and filtering. Index Terms — Boolean Information Retrieval, computational complexity, data models, query languages, satisfiability, entailment, proximity I.
Deciding termination of query evaluation in transitiveclosure logics for constraint databases
, 2003
"... We study extensions of firstorder logic over the reals with different types of transitiveclosure operators as query languages for constraint databases that can be described by Boolean combinations of polynomial inequalities. We are in particular interested in deciding the termination of the evalu ..."
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We study extensions of firstorder logic over the reals with different types of transitiveclosure operators as query languages for constraint databases that can be described by Boolean combinations of polynomial inequalities. We are in particular interested in deciding the termination of the evaluation of queries expressible in these transitiveclosure logics. It turns out that termination is undecidable in general. However, we show that the termination of the transitive closure of a continuous function graph in the twodimensional plane is decidable, and even expressible in firstorder logic over the reals. Based on this result, we identify a particular transitiveclosure logic for which termination of query evaluation is decidable and which is more expressive than firstorder logic. Furthermore, we can define a guarded fragment in which exactly the terminating queries of this language are expressible.
Automated analysis of datadependent programs with dynamic memory
 In ATVA
, 2009
"... Abstract. We present a new approach for automatic verification of datadependent programs manipulating dynamic heaps. A heap is encoded by a graph where the nodes represent the cells, and the edges reflect the pointer structure between the cells of the heap. Each cell contains a set of variables whi ..."
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Abstract. We present a new approach for automatic verification of datadependent programs manipulating dynamic heaps. A heap is encoded by a graph where the nodes represent the cells, and the edges reflect the pointer structure between the cells of the heap. Each cell contains a set of variables which range over the natural numbers. Our method relies on standard backward reachability analysis, where the main idea is to use a simple set of predicates, called signatures, in order to represent bad sets of heaps. Examples of bad heaps are those which contain either garbage, lists which are not wellformed, or lists which are not sorted. We present the results for the case of programs with a single nextselector, and where variables may be compared for (in)equality. This allows us to verify for instance that a program, like bubble sort or insertion sort, returns a list which is wellformed and sorted, or that the merging of two sorted lists is a new sorted list. We report on the result of running a prototype based on the method on a number of programs. 1