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19
DynFO: A Parallel, Dynamic Complexity Class
 Journal of Computer and System Sciences
, 1994
"... Traditionally, computational complexity has considered only static problems. Classical Complexity Classes such as NC, P, and NP are defined in terms of the complexity of checking  upon presentation of an entire input  whether the input satisfies a certain property. For many applications of compu ..."
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Traditionally, computational complexity has considered only static problems. Classical Complexity Classes such as NC, P, and NP are defined in terms of the complexity of checking  upon presentation of an entire input  whether the input satisfies a certain property. For many applications of computers it is more appropriate to model the process as a dynamic one. There is a fairly large object being worked on over a period of time. The object is repeatedly modified by users and computations are performed. We develop a theory of Dynamic Complexity. We study the new complexity class, Dynamic FirstOrder Logic (DynFO). This is the set of properties that can be maintained and queried in firstorder logic, i.e. relational calculus, on a relational database. We show that many interesting properties are in DynFO including multiplication, graph connectivity, bipartiteness, and the computation of minimum spanning trees. Note that none of these problems is in static FO, and this f...
Incremental Validation of XML Documents
 ACM Transactions on Database Systems
, 2004
"... We investigate the incremental validation of XML documents with respect to DTDs, specialized DTDs and XML Schemas, under updates consisting of element tag renamings, insertions and deletions. DTDs are modeled as extended contextfree grammars. “Specialized DTDs ” allow the decoupling of element type ..."
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Cited by 41 (0 self)
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We investigate the incremental validation of XML documents with respect to DTDs, specialized DTDs and XML Schemas, under updates consisting of element tag renamings, insertions and deletions. DTDs are modeled as extended contextfree grammars. “Specialized DTDs ” allow the decoupling of element types from element tags. XML Schemas are abstracted as specialized DTDs with limitations on the type assignment. For DTDs and XML Schemas, we exhibit an O(mlog n) incremental validation algorithm using an auxiliary structure of size O(n), where n is the size of the document and m the number of updates. The algorithm does not handle the incremental validation of XML Schema wrt renaming of internal nodes, which is handled by the specialized DTDs incremental validation algorithm. For specialized DTDs, we provide an O(mlog 2 n) incremental algorithm, again using an auxiliary structure of size O(n). This is a significant improvement over bruteforce revalidation from scratch. We exhibit a restricted class of DTDs called “local ” that arise commonly in practice and for which incremental validation can be done in practically constant time by maintaining only a list of counters. We present implementations of both general incremental validation and local validation on an XML database built on top of a relational database.
The Boundary between Decidability and Undecidability for TransitiveClosure Logics
 In Computer Science Logic (CSL
, 2004
"... To reason effectively about programs, it is important to have some version of a transitiveclosure operator so that we can describe such notions as the set of nodes reachable from a program's variables. On the other hand, with a few notable exceptions, adding transitive closure to even very tam ..."
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Cited by 36 (6 self)
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To reason effectively about programs, it is important to have some version of a transitiveclosure operator so that we can describe such notions as the set of nodes reachable from a program's variables. On the other hand, with a few notable exceptions, adding transitive closure to even very tame logics makes them undecidable. In this paper, we explore...
Local Properties of Query Languages
"... predeterminedportionoftheinput.Examplesincludeallrelationalcalculusqueries. everyrelationalcalculus(rstorder)queryislocal,thegeneralresultsprovedforlocalqueriescan manyeasyinexpressibilityproofsforlocalqueries.Wethenconsideracloselyrelatedproperty, namely,theboundeddegreeproperty.Itdescribestheoutp ..."
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Cited by 33 (23 self)
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predeterminedportionoftheinput.Examplesincludeallrelationalcalculusqueries. everyrelationalcalculus(rstorder)queryislocal,thegeneralresultsprovedforlocalqueriescan manyeasyinexpressibilityproofsforlocalqueries.Wethenconsideracloselyrelatedproperty, namely,theboundeddegreeproperty.Itdescribestheoutputsoflocalqueriesonstructuresthat locallylook\simple."Everyquerythatislocalisshowntohavetheboundeddegreeproperty.Since Westartbyprovingageneralresultdescribingoutputsoflocalqueries.Thisresultleadsto toapplythanEhrenfeuchtFrassegames.Wealsoshowthatsomegeneralizationsofthebounded degreepropertythatwereconjecturedtohold,failforrelationalcalculus. beviewedas\otheshelf"strategiesforprovinginexpressibilityresults,whichareofteneasier maintenanceofviews,andshowthatSQLandrelationalcalculusareincapableofmaintainingthe gregates,whichisessentiallyplainSQL,hastheboundeddegreeproperty,thusansweringaques tionthathasbeenopenforseveralyears.Consequently,rstorderquerieswithHartigorRescher quantiersalsohavetheboundeddegreeproperty.Finally,weapplyourresultstoincremental Wethenprovethatthelanguageobtainedfromrelationalcalculusbyaddinggroupingandag
Incremental Validation of XML Documents
"... We investigate the incremental validation of XML documents with respect to DTDs and XML Schemas, under updates consisting of element tag renamings, insertions and deletions. DTDs are modeled as extended contextfree grammars and XML Schemas are abstracted as "specialized DTDs", allowing to ..."
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Cited by 32 (2 self)
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We investigate the incremental validation of XML documents with respect to DTDs and XML Schemas, under updates consisting of element tag renamings, insertions and deletions. DTDs are modeled as extended contextfree grammars and XML Schemas are abstracted as "specialized DTDs", allowing to decouple element types from element tags. For DTDs, we exhibit an O(m log n) incremental validation algorithm using an auxiliary structure of size O(n), where n is the size of the document and m the number of updates. For specialized DTDs, we provide an O(m log² n) incremental algorithm, again using an auxiliary structure of size O(n). This is a significant improvement over bruteforce revalidation from scratch.
Incremental Recomputation of Recursive Queries with Nested Sets and Aggregate Functions
, 1997
"... We examine the power of incremental evaluation systems that use an SQLlike language for maintaining recursivelydefined views. We show that recursive queries such as transitive closure, and "alternating paths" can be incrementally maintained in a nested relational language, when some a ..."
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Cited by 18 (8 self)
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We examine the power of incremental evaluation systems that use an SQLlike language for maintaining recursivelydefined views. We show that recursive queries such as transitive closure, and "alternating paths" can be incrementally maintained in a nested relational language, when some auxiliary relations are allowed. In the presence of aggregate functions, even more queries can be maintained, for example, the "same generation" query. In contrast, it is still an open problem whether such queries are maintainable in relational calculus. We then restrict the language so that no nested relations are involved (but wekeep the aggregate functions). Such a language captures the capability of most practical relational database systems. We prove that this restriction does not reduce the incremental computational power; that is, any query that can be maintained in a nested language with aggregates, is still maintainable using only flat relations. We also show that one does not need auxiliar...
On Impossibility of Decremental Recomputation of Recursive Queries in Relational Calculus and SQL
 In Proceedings of 5th International Workshop on Database Programming Languages
, 1995
"... We study the problem of maintaining recursivelydefined views, such as the transitive closure of a relation, in traditional relational languages that do not have recursion mechanisms. In particular, we show that the transitive closure cannot be maintained in relational calculus under deletion of edg ..."
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Cited by 15 (8 self)
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We study the problem of maintaining recursivelydefined views, such as the transitive closure of a relation, in traditional relational languages that do not have recursion mechanisms. In particular, we show that the transitive closure cannot be maintained in relational calculus under deletion of edges. We use new proof techniques to show this result. These proof techniques generalize to other languages, for example, to the language for nested relations that also contains a number of aggregate functions. Such a language is considered in this paper as a theoretical reconstruction of SQL. Our proof techniques also generalize to other recursive queries. Consequently, we show that a number of recursive queries cannot be maintained in an SQLlike language. We show that this continues to be true in the presence of certain auxiliary relations. We also relate the complexity of updating transitive closure to that of updating the samegeneration query and show that the latter is strictly harder t...
Maintaining the transitive closure of graphs in SQL
 In Int. J. Information Technology
, 1999
"... It is common knowledge that relational calculus and even SQL are not expressive enough to express recursive queries such as the transitive closure. In a real database system, one can overcome this problem by storing a graph together with its transitive closure and maintaining the latter whenever upd ..."
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Cited by 8 (2 self)
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It is common knowledge that relational calculus and even SQL are not expressive enough to express recursive queries such as the transitive closure. In a real database system, one can overcome this problem by storing a graph together with its transitive closure and maintaining the latter whenever updates to the former occur. This leads to the concept of an incremental evaluation system, or IES. Much is already known about the theory of IES but very little has been translated into practice. The purpose of this paper is to ll in this gap by providing a gentle introduction to and an overview of some recent theoretical results on IES. The introduction is through the translation into SQL of three interesting positive maintenance results that have practical importance { the maintenance of the transitive closure of acyclic graphs, of undirected graphs, and of arbitrary directed graphs. Interestingly, these examples also allow ustoshow the relationship between power and cost in the incremental maintenance of database queries. 1
Separating Auxiliary Arity Hierarchy of FirstOrder Incremental Evaluation Using (3k+1)ary Input Relations
 International Journal of Foundations of Computer Science
, 1997
"... this paper by reducing 3k + 1 to k + 1, or k, or even a constant. We will prove this by modifying Cai's result [3] and by modifying the reduction used in [7]. Section 2 provides a brief review the notion of "firstorder incremental evaluation systems ". Section 3 establishes a necessa ..."
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Cited by 8 (3 self)
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this paper by reducing 3k + 1 to k + 1, or k, or even a constant. We will prove this by modifying Cai's result [3] and by modifying the reduction used in [7]. Section 2 provides a brief review the notion of "firstorder incremental evaluation systems ". Section 3 establishes a necessary technical lemma, which is a variant of Cai's theorem. Section 4 gives the proof of the above theorem. 2 FirstOrder Incremental Evaluation Systems
Incremental maintenance of shortest distance and transitive closure in firstorder logic and sql
 ACM Trans. Database Syst
"... Given a database, the view maintenance problem is concerned with the efficient computation of the new contents of a given view when updates to the database happen. We consider the view maintenance problem for the situation when the database contains a (weighted) graph and the view is either the tran ..."
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Cited by 6 (2 self)
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Given a database, the view maintenance problem is concerned with the efficient computation of the new contents of a given view when updates to the database happen. We consider the view maintenance problem for the situation when the database contains a (weighted) graph and the view is either the transitive closure or the answer to the allpairs shortestdistance problem (APSD). We give incremental algorithms for (APSD), which support both edge insertions and deletions. For transitive closure, the algorithm is applicable to a more general class of graphs than those previously explored. Our algorithms use firstorder queries, along with addition (+) and lessthan (<) operations (F O(+, <)); they store O(n 2) number of tuples, where n is the number of vertices, and have AC 0 data complexity for integer weights. Since F O(+, <) is a sublanguage of SQL and is supported by almost all current database systems, our maintenance algorithms are more appropriate for database applications than nondatabase query type of maintenance algorithms.