Jan Chomicki

• University at Buffalo, State University of New York

Data exchange is the problem of transforming data that is structured under the source schema into data structured under another schema, called the target schema, so that both source and target data satisfy the relationship between the schemas. Many applications such as planning, scheduling, medical and fraud detection systems, require data exchange...

Data exchange is the problem of transforming data that is structured under a source schema into data structured under another schema, called the target schema, so that both the source and target data satisfy the relationship between the schemas. Even though the formal framework of data exchange for relational database systems is well-established, i...

Skylines assume that all attributes are equally important, as each dimension can always be traded off for another. Prioritized skylines (p-skylines) take into account non-compensatory preferences, where some dimensions are deemed more important than others, and trade-offs are constrained by the relative importance of the attributes involved. In thi...

Skyline queries are a popular way to obtain preferred answers from the database by providing only the orderings of attribute values. The result of a skyline query consists of those input tuples for which there is no input tuple having better or equal values in all the attributes and a better value in at least one attribute. In this article, we summ...

We propose a “logic + SQL” framework for set preferences. Candidate best sets are represented using profiles consisting of scalar features. This reduces set preferences to tuple preferences over set profiles. We propose two optimization techniques: superpreference and M-relation. Superpreference targets dominated profiles. It reduces the input size...

We summarize here recent research on obtaining consistent information from inconsistent databases. We describe the underlying semantic model and a number of approaches to computing consistent query answers. We conclude by outlining further research directions in this area.

Preference queries incorporate the notion of binary preference relation into relational database querying. Instead of returning all the answers, such queries return only the best answers, according to a given preference relation. Preference queries are a fast growing area of database research. Skyline queries constitute one of the most thoroughly s...

A consistent query answer in an inconsistent database is an answer obtained in every (minimal) repair. The repairs are obtained by resolving all conflicts in all possible ways. Often, however, the user is able to provide a preference on how conflicts should be resolved. We investigate here the framework of preferred consistent query answers, in whi...

Querying databases with preferences is an important re- search problem. Among various approaches to querying with preferences, the skyline framework is one of the most pop- ular. A well known deciency of that framework is that all attributes are of the same importance in skyline pref- erence relations. Consequently, the size of the results of skyli...

The binary relation framework has been shown to be applicable to many real-life preference handling scenarios. Here we study preference contraction: the problem of discarding selected preferences. We argue that the property of minimality and the preservation of strict partial orders are crucial for contractions. Contractions can be further constrai...

This paper addresses the problem of representing the set of repairs of a possibly inconsistent database by means of a disjunctive database. Specifically, the class of denial constraints is considered. We show that, given a database and a set of denial constraints, there exists a (unique) disjunctive database, called canonical, which represents the...

We study here fundamental issues involved in top-k query evaluation in probabilistic databases. We consider simple probabilistic databases in which probabilities are associated with individual tuples, and general probabilistic databases in which, additionally, exclusivity relationships between tuples can be represented. In contrast to other recent...

The framework of consistent query answers and repairs has been introduced to alleviate the impact of inconsistent data on the answers to a query. A repair is a minimally different consistent instance and an answer is consistent if it is present in every repair. In this article we study the complexity of consistent query answers and repair checking...

Usually, the data in a database instance is supposed to be consistent and satisfy the database integrity constraints. However, it is quite common for the two to diverge. The data may fail to satisfy the constraints for various reasons: it may be erroneous, out of date, or come from mutually inconsistent sources.

We study here fundamental issues involved in top-k query evaluation in probabilistic databases. We consider simple probabilistic databases in which probabilities are associated with individual tuples, and general probabilistic databases in which, additionally, exclusivity relationships between tuples can be represented. In contrast to other recent...

We investigate the problem of querying (regular) sets of XML documents represented with tree automata and we consider $n$-ary tree automata queries whose expressive power captures MSO on trees. Because finite automata can represent infinite sets of documents, we propose the notions of {\em universal} and {\em existential} query answers, answers tha...

We propose a logical framework for set preferences. Candidate sets are represented using profiles consisting of scalar features. This reduces set pref- erences to tuple preferences over set profiles. We also give a heuristic algorithm for the computation of the "best" sets.

Changing preferences is very common in real life. The ex- pressive power of the operations of preference change intro- duced so far in the literature is limited to adding new informa- tion about preference and equivalence. Here, we discuss the operation of discarding preferences: preference contraction. We argue that the property of minimality and...

Preference queries are relational algebra or SQL queries that contain occurrences of the winnow operator (find the most preferred tuples in a given relation). Such queries are parameterized by specific preference relations. Semantic optimization techniques make use of integrity constraints holding in the database. In the context of semantic optimiz...

Constraint LTL, a generalisation of LTL over Presburger constraints, is often used as a formal language to specify the behavior of operational models with constraints. The freeze quantifier can be part of the language, as in some real-time logics, but ...

Consistent query answering (CQA) is an approach to query- ing inconsistent databases without repairing them first. This invited talk introduces the basics of CQA, and discusses selected issues in this area. The talk concludes with a summary of other relevant work and an outline of potential future research topics.

We present here a variant of acyclic CP-networks. It allows not only finite but also infinite domain attributes. It also has the property that a preference over each attribute in the network has higher priority then all the descendants' prefer-ences. We provide an algorithm of constructing a preference formula representing the order induced by a hi...

We propose constraint databases as an intermediate level facilitating the interoperability of spatiotemporal data models. Constraint query languages are used to express translations between different data models. We illustrate our approach in the context of a number of temporal, spatial and spatiotemporal data models.

This paper briefly reviews the recent literature on consistent query answering, an approach to handle database inconsistency in a systematic and logical manner based on the notion of repair. It discusses some computational and semantic limitations of consistent query answering, and summarizes selected research directions in this area.

We define formal notions of temporal domain and temporal database, and use them to survey a wide spectrum of temporal query languages. We distinguish between an abstract temporal database and its concrete representations, and accordingly between abstract and concrete temporal query languages. We also address the issue of incomplete temporal informa...

We present here a formal foundation for an iterative and incremental approach to constructing and evaluating preference queries. Our main focus is on query modification: a query transformation approach which works by revising the preference relation in the query. We provide a detailed analysis of the cases where the order-theoretic properties of th...

There has been interest recently in skyline queries, also called Pareto queries, on relational databases. Relational query languages do not support search for “best” tuples, beyond the order by statement. The proposed skyline operator allows one to query for best tuples with respect to any number of attributes as preferences. In this work, we explo...

We consider the problem of querying XML documents which are not valid with respect to given DTDs. We propose a framework for measuring the invalidity of XML documents and compactly representing minimal repair- ing scenarios. Furthermore, we present a validity-sensitive method of querying XML documents, which extracts more information from invalid X...

One of the goals of cleaning an inconsistent database is to remove conflicts between tuples. Typically, the user specifies how the conflicts should be resolved. Sometimes this specification is incomplete, and the cleaned database may still be inconsistent. At the same time, data cleaning is a rather drastic approach to conflict resolution: It remov...

We present here a formal foundation for an iterative and incremental approach to constructing and evaluating preference queries. Our main focus is on query modification: a query transformation approach which works by revising the preference relation in the query. We provide a detailed analysis of the cases where the order-theoretic properties of th...

Traditionally, dependency theory has been developed for uninterpreted data. Specifically, the only assumption that is made about the data domains is that data values can be compared for equality. However, data is often interpreted and there can be advantages in considering it as such, for instance obtaining more compact representations as done in c...

This paper briefly reviews the recent literature on consistent query answering, an approach to handle database inconsistency in a systematic and logical manner based on the notion of repair. It discusses some computational and semantic limitations of consistent query answering, and summarizes selected research directions in this area

The highlights of 'ARISE/NISR Workshop on Exchange and Integration of Data' held at the IBM Center for Advanced Studies, Toronto Lab, between October 7-9, 2004 are discussed. Research around the management, mapping, and intregration of database schemata is relevant to both data exchange and integration. The goal of data integration is to provide a...

We study here the impact of priorities on conflict resolution in inconsistent relational databases. We extend the framework of repairs and consistent query answers. We propose a set of postulates that an extended framework should satisfy and consider two instantiations of the framework: (locally preferred) l-repairs and (globally preferred) g-repai...

We study here preference revision, considering both the monotonic case where the original preferences are preserved and the nonmonotonic case where the new preferences may override the original ones. We use a relational framework in which preferences are represented using binary relations (not necessarily finite). We identify several classes of rev...

We address the problem of minimal-change integrity main- tenance in the context of integrity constraints in relational databases. Using the framework proposed by Arenas, Bertossi, and Chomicki (4), we focus on two basic computational issues: repair checking (is a database instance a repair of a given database?) and consistent query answers (is a tu...

A consistent query answer in a possibly inconsistent database is an answer which is true in every (minimal) repair of the database. We present here a practical framework for computing consistent query answers for large, possibly inconsistent relational databases. We consider relational algebra queries without projection, and denial constraints. Bec...

A consistent query answer in a possibly inconsistent database is an answer which is true in every (minimal) repair of the database. We present here a practical framework for computing consistent query answers for large, possibly inconsistent relational databases. We consider relational algebra queries without projection, and denial constraints. Bec...

Preference queries are relational algebra or SQL queries that contain occurrences of the winnow operator (find the most preferred tuples in a given relation). We present here a number of semantic optimization techniques applicable to preference queries. The techniques make it possible to remove redundant occurrences of the winnow operator and to ap...

Integrity constraints express important properties of data, but the task of preserving data consistency is becoming increasingly problematic with new database applications. For example, in the case of integration of several data sources, even if the sources are separately consistent, the integrated data can violate the integrity constraints. The tr...

We summarize here recent research on obtaining consistent informa- tion from inconsistent databases. We describe the underlying semantic model and a number of approaches to computing consistent query an- swers. We conclude by outlining further research directions in this area.

In this era of heterogeneous and distributed data sources, ranging from semistructured documents to knowledge about coordination processes or workflows, logic provides a rich set of tools and techniques with which to address the questions of how to represent, query and reason about complex data. This book provides a state-of-the-art overview of res...

The handling of user preferences is becoming an increasingly important issue in present-day information systems. Among others, preferences are used for information filtering and extraction to reduce the volume of data presented to the user. They are also used to keep track of user profiles and formulate policies to improve and automate decision mak...

We present a data model for spatio-temporal databases. In this model spatiotemporal data is represented as a finite union of objects described by means of a spatial reference object, a temporal object and a geometric transformation function that determines the change or movement of the reference object in time. We define a number of practically rel...

In this paper we study constraint databases with variable independence conditions (vics). Such databases occur naturally in the context of temporal and spatiotemporal database applications. Using computational geometry techniques, we show that variable independence is decidable for linear constraint databases. We also present a set of rules for inf...

In this chapter, we summarize the research on querying inconsistent databases that we have been conducting during the last five years. The formal framework that we have used is based on two concepts: repair and consistent query answer. We describe different approaches to the issue of computing consistent query answers: query transformation, logic p...

In this paper we consider the problem of the logical characterization of the notion of consistent answer in a relational database that may violate given integrity constraints. This notion is captured in terms of the possible repaired versions of the database. A method for computing consistent answers is given and its soundness and completeness (for...

The skyline, or Pareto, operator selects those tuples that are not dominated by any others. Extending relational systems with the skyline operator would offer a basis for handling preference queries. Good algorithms are needed for skyline, however, to make this efficient in a relational setting. We propose a skyline algorithm, SFS, based on presort...

This paper addresses issues involved in applying the event-condition-action (ECA) rule paradigm of active databases to policies-collections of general principles specifying the desired behavior of a system. We use a declarative policy description language, PDL, in which policies are formulated as sets of ECA rules. The main contribution of the pape...

We address the problem of minimal-change integrity maintenance in the context of integrity constraints in relational databases. We assume that integrity-restoration actions are limited to tuple deletions. We focus on two basic computational issues: repair checking (is a database instance a repair of a given database?) and consistent query answers [...

We address the problem of minimal-change integrity maintenance in the context of integrity constraints in relational databases. We assume that integrity-restoration actions are limited to tuple deletions. We identify two basic computational issues: repair checking (is a database instance a repair of a given database?) and consistent query answers (...

The handling of user preferences is becoming an increasingly important issue in present-day information systems. Among others, preferences are used for information filtering and extraction to reduce the volume of data presented to the user. They are also used to keep track of user profiles and formulate policies to improve and automate decision mak...

A relational database is inconsistent if it does not satisfy a given set of integrity constraints. Nevertheless, it is likely that most of the data in it is consistent with the constraints. In this paper we apply logic programming based on answer sets to the problem of retrieving consistent information from a possibly inconsistent database. Since c...

We consider here scalar aggregation queries in databases that may violate a given set of functional dependencies. We define consistent answers to such queries to be greatest-lowest/least-upper bounds on the value of the scalar function across all (minimal) repairs of the database. We show how to compute such answers. We provide a complete character...

Introduction In this chapter, we address the issue of obtaining consistent information from inconsistent databases -- databases that violate given integrity constraints. Our basic assumption departs from everyday practice of database management systems. Typically, a database management system checks the satisfaction of integrity constraints and bac...

We are now in an era of intensive earth observation. Orbital platforms generate myriad remote sensing datastreams across a range of spatial, temporal, spectral, and radiometric resolutions. The number and variety of "eyes in the skies" are scheduled to increase significantly over the next few years. This veritable data deluge necessitates new ways...

We consider here the problem of obtaining reliable, consistent information from inconsistent databases -- databases that do not have to satisfy given integrity constraints. We use the notion of consistent query answer -- a query answer which is true in every (minimal) repair of the database. We provide a complete classification of the computational...

The handling of user preferences is becoming an increasingly important issue in present-day information systems. Among others, pref- erences are used for information flltering and extraction to reduce the volume of data presented to the user. They are also used to keep track of user proflles and formulate policies to improve and automate decision m...

Databases may be inconsistent with respect to a given set of integrity constraints. Nevertheless, most of the data may be consistent. In this paper we show how to specify consistent data and how to query a relational database in such a way that only consistent data is retrieved. The specification and queries axe based on disjunctive extended logic...

When data sources are integrated into a single global system, inconsistencies wrt global integrity constraints are likely to occur. In this paper, the notion of consistent answer to a global query in the context of the local-as-view approach to data integration is characterized. Furthermore, a methodology for generating query plans for retrieving c...

As Conference Chair, it is my pleasure to welcome you to dg.o 2002, the second annual National Conference on Digital Government Research. Dg.o 2002 is the only national conference to bring together computer- and social science researchers, government officials ...

We establish a correspondence between temporal logic and a subset of ATSQL, a temporal extension of SQL{92. In addition, we provide an eective translation from temporal logic to ATSQL that enables a user to write high-level queries which are then evaluated against a space-ecient representation of the database. A reverse translation, also provided i...

We investigate the issue of conflict detection and resolution for policies formulated as sets of event-condition-action rules. We focus on the temporal dimension of policies. In particular, we consider sequence events in rules, conflict resolution through cancellation or delay, and temporal action constraints. We formally define monitors — procedur...

We propose an extension of classical predicate calculus, called Transaction Logic, which provides a logical foundation for the phenomenon of state changes in logic programs and databases. Transaction Logic comes with a natural model theory and a sound and complete proof theory. The proof theory not only verifies programs, but also executes them, wh...

We consider here scalar aggregation queries in databases that may violate a given set of functional dependencies. We show how to compute consistent answers (answers true in every minimal repair of the database) to such queries. We provide a complete characterization of the computational complexity of this problem. We also show how tractability can...

Aggregation operators like COUNT, SUM, and AVG form an indispensable part of database query languages for the relational data model. As constraint query languages give a natural analog of relational calculus in the geometric context, a crucial question concerns how to extend standard aggregation constructs from the relational model to the geometric...

The simple event-condition-action (ECA) rule paradigm of active databases has proved very useful in many AI and database applications. However, its applicability goes beyond data management. ECA rules can be used in network management and monitoring, electronic commerce, security and access management, and other application areas to express policie...

We propose constraint databases as an intermediate level facilitating the interoperability of spatiotemporal data models. Constraint query languages are used to express translations between different data models. We illustrate our approach in the context of a number of temporal, spatial, and spatiotemporal data models.

Traditionally, dependency theory has been developed for uninterpreted data. Specifically, the only assumption that is made about the data domains is that data values can be compared for equality. However, data is often interpreted and there can be advantages in considering data as such, for instance, obtaining more compact representations as is don...

. Constraint databases provide a very expressive framework for spatiotemporal database applications. However, animating such databases is difficult because of the cost of constructing a graphical representation of a single snapshot of a constraint database. We present a novel approach that makes the efficient animation of constraint databases possi...

In this paper we consider the problem of the logical characterization of the notion of consistent answer in a relational database that may violate given integrity constraints. This notion is captured in terms of the possible repaired versions of the database. A method for computing consistent answers is given and its soundness and completeness (for...

We present a framework for specifying spatiotemporal objects using spatial and temporal objects, and a geometric transformation. We define a number of classes of spatiotemporal objects and study their closure properties

Temporal Databases 34 3.2.2 Relational Database Histories 36 3.3 Temporal Queries 36 3.3.1 Abstract Temporal Query Languages 37 3.3.2 Expressive Power 41 3.3.3 Space-efficient Encoding of Temporal Databases 44 3.3.4 Concrete Temporal Query Languages 46 3.3.5 Evaluation of Abstract Query Languages using Compilation 47 3.3.6 SQL and Derived Temporal...

In this paper we introduce a generalization of Datalog that operates on periodicity constraints over integers. We develop a closed-form bottom-up evaluation procedure for this class of constraints. We also develop a closed-form bottom-up query evaluation procedure for the class of periodic constraints combined with gap-order constraints. We provide...

We propose a novel protocol for aggregating micropayments in a networked environment. The protocol is based on the idea of debt consolidation and is fully decentralized. We propose client-server and serverless versions of the protocol. We also analyze the mathematical properties of the protocol. Finally, we show how basic cryptographic techniques c...

this paper.) Finally, by having ICs expressed in logic, one can use deduction and logic as one's basic and natural tools for handling, and reasoning over, database specifications (facts, rules, queries, and ICs). This applies for relational databases, with or without rules, and can be applied to object-oriented and object-relational databases as we...

The designers and users of present-day information systems deal with more and more complex applications that have to meet stringent quality requirements. It is no longer enough to capture the static aspect of the world — modeling the dynamics, i.e., time, change, and concurrency becomes equally important. Also, there is a need for multiple modaliti...

Temporal logic is obtained by adding temporal connectives to a logic language. Explicit references to time are hidden inside the temporal connectives. Different variants of temporal logic use different sets of such connectives. In this chapter, we survey the fundamental varieties of temporal logic and describe their applications in information syst...

The authors consider the problem of logical characterization of the notion of correct answers in a relational database that may violate given integrity constraints. This notion is captured in terms of the possible repaired versions of the database. A computational counterpart of the semantic notion is provided in terms of the reconstruction of the...

Time is ubiquitous in information systems. Almost every enterprise faces the problem of its data becoming out of date. However, such data is often valu­ able, so it should be archived and some means to access it should be provided. Also, some data may be inherently historical, e.g., medical, cadastral, or ju­ dicial records. Temporal databases prov...

ing of Temporal Databases and Temporal Query Languages. We briefly survey the classical results. However, the main emphasis is on recent developments in the area of temporal databases. In the light of several recent results [Abiteboul et al., 1996, Chomicki and Kuper, 1995, Chomicki et al., 1996, Kanellakis et al., 1995, Toman and Niwinski, 1996, T...

We propose constraint databases as an intermediate level facilitating the interoperability of spatiotemporal data models. Constraint query languages are used to express translations between different data models. We illustrate our approach in the context of a number of temporal, spatial and spatiotemporal data models.

We discuss the issue of adding aggregation to constraint databases. Previous work has shown that, in general, adding aggregates to constraint databases results in languages that are not closed. We show that by imposing a natural restriction, called variable independence (which is a generalization of the assumptions underlying the classical relation...

We present here a depth-bounded bottom-up evaluation algorithm for logic programs. We show that it is sound, complete, and terminating for finite-answer queries if the programs are syntactically restricted to DatalognS, a class of logic programs with limited function symbols. DatalognS is an extension of Datalog capable of representing infinite phe...

The paper proposes a general architecture for implementing temporal integrity constraints by compiling them into a set of active DBMS rules. The modularity of the design allows easy adaptation to different environments. Both differences in the specification languages and in the target rule systems can be easily accommodated. The advantages of this...

We present an efficient implementation method for temporal integrity constraints formulated in Past Temporal Logic. Although the constraints can refer to past states of the database, their checking does not require that the entire database history be stored. Instead, every database state is extended with auxiliary relations that contain the histori...

)Jan ChomickiKansas State Universitychomicki@cis.ksu.eduGabriel KuperECRCkuper@ecrc.deAbstractWe define a new aggregation operator ?￥n for constraintdatabases that makes it possible to measure infinite subsetsof the n-dimensional space defined by constraints. Weshow that it is well defined for real linear arithmeticconstraints and integer linear ar...

The system presented in this paper allows automatic and efficient translation of integrity constraints formulated in past temporal logic into rules of the Starburst DBMS. During the compilation, the set of constraints is checked for the safe evaluation property. The result of the compilation is a set of Starburst SQL statements that define all the...