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21
Modeling and Querying Moving Objects
, 1997
"... In this paper we propose a data model for representing moving objects in database systems. It is called the Moving Objects SpatioTemporal (MOST) data model. We also propose Future Temporal Logic (FTL) as the query language for the MOST model, and devise an algorithm for processing FTL queries in MO ..."
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Cited by 254 (18 self)
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In this paper we propose a data model for representing moving objects in database systems. It is called the Moving Objects SpatioTemporal (MOST) data model. We also propose Future Temporal Logic (FTL) as the query language for the MOST model, and devise an algorithm for processing FTL queries in MOST. 1. Introduction Existing database management systems (DBMS's) are not well equipped to handle continuously changing data, such as the position of moving objects. The reason for this is that in databases, data is assumed to be constant unless it is explicitly modified. For example, if the salary field is 30K, then this salary is assumed to hold (i.e. 30K is returned in response to queries) until explicitly updated. Thus, in order to represent moving objects (e.g. cars) in a database, and answer queries about their position (e.g., How far is the car with license plate RWW860 from the nearest hospital?) the car's position has to be continuously updated. This is unsatisfactory since either ...
Moving Objects Databases: Issues and Solutions
, 1998
"... Consider a database that represents information about moving objects and their location. For example, for a database representing the location of taxicabs a typical query may be: retrieve the free cabs that are currently within 1 mile of 33 N. Michigan Ave., Chicago (to pickup a customer). In the ..."
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Cited by 173 (5 self)
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Consider a database that represents information about moving objects and their location. For example, for a database representing the location of taxicabs a typical query may be: retrieve the free cabs that are currently within 1 mile of 33 N. Michigan Ave., Chicago (to pickup a customer). In the military, moving objects database applications arise in the context of the digital battlefield, and in the civilian industry they arise in transportation systems. Currently, moving objects database applications are being developed in an ad hoc fashion. Database Management System (DBMS) technology provides a potential foundation upon which to develop these applications, however, DBMS's are currently not used for this purpose. The reason is that there is a critical set of capabilities that are needed by moving objects database applications and are lacking in existing DBMS's. The objective of our Databases fOr MovINg Objects (DOMINO) project is to build an envelope containing these capabilities...
Updating and Querying Databases that Track Mobile Units
"... In this paper we consider databases representing information about moving objects (e.g. vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (name ..."
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Cited by 155 (12 self)
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In this paper we consider databases representing information about moving objects (e.g. vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (namely its database location) should be updated. We answer this question by proposing an information cost model that captures uncertainty, deviation, and communication. Then we analyze deadreckoning policies, namely policies that update the database location whenever the distance between the actual location and the database location exceeds a given threshold, x. Deadreckoning is the prevalent approach in military applications, and our cost model enables us to determine the threshold x. We propose several deadreckoning policies and we compare their performance by simulation. Then we consider the problem of processing range queries in the database. An example of a range query is `retrieve the ob...
Tableau Techniques For Querying Information Sources Through Global Schemas
 In Proc. of the 7th Int. Conf. on Database Theory (ICDT'99), volume 1540 of Lecture Notes in Computer Science
, 1999
"... . The foundational homomorphism techniques introduced by Chandra and Merlin for testing containment of conjunctive queries have recently attracted renewed interest due to their central role in information integration applications. We show that generalizations of the classical tableau representation ..."
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Cited by 118 (6 self)
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. The foundational homomorphism techniques introduced by Chandra and Merlin for testing containment of conjunctive queries have recently attracted renewed interest due to their central role in information integration applications. We show that generalizations of the classical tableau representation of conjunctive queries are useful for computing query answers in information integration systems where information sources are modeled as views defined on a virtual global schema. We consider a general situation where sources may or may not be known to be correct and complete. We characterize the set of answers to a global query and give algorithms to compute a finite representation of this possibly infinite set, as well as its certain and possible approximations. We show how to rewrite a global query in terms of the sources in two special cases, and show that one of these is equivalent to the Information Manifold rewriting of Levy et al. 1 Introduction Information Integration systems [Ull...
Cost and Imprecision in Modeling the Position of Moving Objects
, 1998
"... Consider a database that represents the location of moving objects, such as taxicabs (typical query: retrieve the cabs that are currently within 1 mile of 33 Michigan Ave., Chicago), or objects in a battlefield. Existing database management systems (DBMS's) are not well equipped to handle continuo ..."
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Cited by 83 (7 self)
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Consider a database that represents the location of moving objects, such as taxicabs (typical query: retrieve the cabs that are currently within 1 mile of 33 Michigan Ave., Chicago), or objects in a battlefield. Existing database management systems (DBMS's) are not well equipped to handle continuously changing data, such as the position of moving objects, since data is assumed to be constant unless it is explicitly modified. In this paper we address positionupdate policies and imprecision. Namely, assuming that the actual position of a moving object m deviates from the position computed by the DBMS, when should m update its position in the database in order to eliminate the deviation? Furthermore, how can the DBMS provide a bound on the error (i.e. the deviation) when it replies to a query: what is the current position of m? We propose a cost based approach to update policies that answers both questions. We develop several update policies and analyze them theoretically and experime...
Relational Expressive Power of Constraint Query Languages
 Journal of the ACM
, 1995
"... The expressive power of firstorder query languages with several classes of equality and inequality constraints is studied in this paper. We settle the conjecture that recursive queries such as parity test and transitive closure cannot be expressed in the relational calculus augmented with polynomia ..."
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Cited by 76 (18 self)
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The expressive power of firstorder query languages with several classes of equality and inequality constraints is studied in this paper. We settle the conjecture that recursive queries such as parity test and transitive closure cannot be expressed in the relational calculus augmented with polynomial inequality constraints over the reals. Furthermore, noting that relational queries exhibit several forms of genericity, we establish a number of collapse results of the following form: The class of generic boolean queries expressible in the relational calculus augmented with a given class of constraints coincides with the class of queries expressible in the relational calculus (with or without an order relation). We prove such results for both the natural and activedomain semantics. As a consequence, the relational calculus augmented with polynomial inequalities expresses the same classes of generic boolean queries under both the natural and activedomain semantics. In the course of proving...
A Query Language Based on the Ambient Logic
, 2001
"... The ambient logic is a modal logic proposed to describe the structural and computational properties of distributed and mobile computation. The structural part of the ambient logic is, essentially, a logic of labeled trees, hence it turns out to be a good foundation for query languages for semistruct ..."
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Cited by 62 (11 self)
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The ambient logic is a modal logic proposed to describe the structural and computational properties of distributed and mobile computation. The structural part of the ambient logic is, essentially, a logic of labeled trees, hence it turns out to be a good foundation for query languages for semistructured data, much in the same way as first order logic is a fitting foundation for relational query languages. We define here a query language for semistructured data that is based on the ambient logic, and we outline an execution model for this language. The language turns out to be quite expressive. Its strong foundations and the equivalences that hold in the ambient logic are helpful in the definition of the language semantics and execution model.
Querying the Uncertain Position of Moving Objects
 In Temporal Databases: Research and Practice
, 1998
"... In this paper we propose a data model for representing moving objects with uncertain positions in database systems. It is called the Moving Objects SpatioTemporal (MOST) data model. We also propose Future Temporal Logic (FTL) as the query language for the MOST model, and devise an algorithm for pro ..."
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Cited by 47 (4 self)
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In this paper we propose a data model for representing moving objects with uncertain positions in database systems. It is called the Moving Objects SpatioTemporal (MOST) data model. We also propose Future Temporal Logic (FTL) as the query language for the MOST model, and devise an algorithm for processing FTL queries in MOST. 1 Introduction Existing database management systems (DBMS's) are not well equipped to handle continuously changing data, such as the position of moving objects. The reason for this is that in databases, data is assumed to be constant unless it is explicitly modified. For example, if the salary field is 30K, then this salary is assumed to hold (i.e. 30K is returned in response to queries) until explicitly updated. Thus, in order to represent moving objects (e.g. cars) in a database, and answer queries about their position (e.g., How far is the car with license plate RWW860 from the nearest hospital?) the car's position has to be continuously updated. This is unsa...
Variable Independence and Aggregation Closure
 IN ACM SYMPOSIUM ON PRINCIPLES OF DATABASE SYSTEMS
, 1996
"... 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 ..."
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Cited by 31 (10 self)
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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 relational model of data) on the schema, we can guarantee that a restricted version of the language with aggregation is closed. We illustrate our approach in the context of linear constraint databases.
On the Structure of Queries in Constraint Query Languages
 In Proceedings of IEEE Symposium on Logic in Computer Science
, 1996
"... We study the structure of firstorder and secondorder queries over constraint databases. Constraint databases are formally modeled as finite relational structures embedded in some fixed infinite structure. We concentrate on problems of elimination of constraints, reducing quantification range to the ..."
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Cited by 27 (11 self)
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We study the structure of firstorder and secondorder queries over constraint databases. Constraint databases are formally modeled as finite relational structures embedded in some fixed infinite structure. We concentrate on problems of elimination of constraints, reducing quantification range to the active domain of the database and obtaining new complexity bounds. We show that for a large class of signatures, including real arithmetic constraints, unbounded quantification can be eliminated. That is, one can transform a sentence containing unrestricted quantification over the infinite universe of discourse to get an equivalent sentence in which quantifiers range over the finite relational structure. We use this result to get a new complexity upper bound on the evaluation of real arithmetic constraints. We also expand upon techniques in [20] and [4] for getting upper bounds on the expressiveness of constraint query languages, and apply it to a number of firstorder and secondorder quer...