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50
Dynamic tree isomorphism via firstorder updates
 In: PODS, ACM Press
, 1998
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On Impossibility of Decremental Recomputation of Recursive Queries in Relational Calculus and SQL
, 1995
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Making Aggregate Views SelfMaintainable
 Data Knowledge Engineering
, 1999
"... Data in the warehouse can be seen as materialized views generated from the underlying multiple data sources. Materialized views are used to speed up query processing on large amounts of data. These views need to be maintained in response to updates in the source data. This is often done using increm ..."
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Data in the warehouse can be seen as materialized views generated from the underlying multiple data sources. Materialized views are used to speed up query processing on large amounts of data. These views need to be maintained in response to updates in the source data. This is often done using incremental techniques that access data from underlying sources. In the data warehousing scenario, accessing base relations can be difficult, sometimes data sources may be unavailable, since these relations are distributed across different sources. For these reasons, the issue of selfmaintainability of the view is an important issue in data warehousing. In this paper we show that the warehouse views can be made selfmaintainable if some additional relations, called auxiliary relations, derived from the intermediate results of the view computation can be materialized in the warehouse. We give an algorithm for determining what auxiliary relations need to be materialized in order to make a materiali...
Incremental recomputation in local languages.
 Inf. Comput.
, 2003
"... Abstract We study the problem of maintaining recursively defined views, such as the transitive closure of a relation, in traditional relational languages that do not have recursion mechanisms. The main results of this paper are negative ones: we show that a certain property of query languages impli ..."
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Abstract We study the problem of maintaining recursively defined views, such as the transitive closure of a relation, in traditional relational languages that do not have recursion mechanisms. The main results of this paper are negative ones: we show that a certain property of query languages implies impossibility of such incremental maintenance. The property we use is locality of queries, which is known to hold for relational calculus and various extensions, including those with grouping and aggregate constructs (essentially, plain SQL).
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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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.
Dynamic Complexity Theory Revisited
 Proc. Annual Symposium on Theoretical Aspects of Computer Science (STACS 05), Springer LNCS 3404, 2005
, 2005
"... Abstract. Dynamic complexity asks for the effort needed to maintain the information about properties of a structure under operations changing the structure. This paper introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the basic structural com ..."
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Abstract. Dynamic complexity asks for the effort needed to maintain the information about properties of a structure under operations changing the structure. This paper introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFLcomplete problem D2LREACH(acyclic) can be maintained with firstorder updates. 1
Toward expressive syndication on the web
 In Proc. of the 16th Int. World Wide Web Conference (WWW
, 2007
"... Syndication systems on the Web have attracted vast amounts of attention in recent years. As technologies have emerged and matured, there has been a transition to more expressive syndication approaches; that is, subscribers and publishers are provided with more expressive means of describing their in ..."
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Syndication systems on the Web have attracted vast amounts of attention in recent years. As technologies have emerged and matured, there has been a transition to more expressive syndication approaches; that is, subscribers and publishers are provided with more expressive means of describing their interests and published content, enabling more accurate information filtering. In this paper, we formalize a syndication architecture that utilizes expressive Web ontologies and logicbased reasoning for selective content dissemination. This provides finer grained control for filtering and automated reasoning for discovering implicit subscription matches, both of which are not achievable in less expressive approaches. We then address one of the main limitations with such a syndication approach, namely matching newly published information with subscription requests in an efficient and practical manner. To this end, we investigate continuous query answering for a large subset of the Web Ontology Language (OWL); specifically, we formally define continuous queries for OWL knowledge bases and present a novel algorithm for continuous query answering in a large subset of this language. Lastly, an evaluation of the query approach is shown, demonstrating its effectiveness for syndication purposes. Categories and Subject Descriptors
Reactors: A dataoriented synchronous/asynchronous programming model for distributed applications
 Theoretical Computer Science
, 2009
"... Abstract. Our aim is to define the kernel of a simple and uniform programming modelthe reactor modelsuitable for building and evolving internetscale programs. A reactor consists of two principal components: mutable state, in the form of a fixed collection of relations, and code, in the form of a ..."
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Abstract. Our aim is to define the kernel of a simple and uniform programming modelthe reactor modelsuitable for building and evolving internetscale programs. A reactor consists of two principal components: mutable state, in the form of a fixed collection of relations, and code, in the form of a fixed collection of rules in the style of datalog. A reactor's code is executed in response to an external stimulus, which takes the form of an attempted update to the reactor's state. As in classical process calculi, the reactor model accommodates collections of distributed, concurrently executing processes. However, unlike classical process calculi, our observable behaviors are sequences of states, rather than sequences of messages. Similarly, the interface to a reactor is simply its state, rather than a collection of message channels, ports, or methods. One novel feature of our model is the ability to compose behaviors both synchronously and asynchronously. Also, our use of datalogstyle rules allows aspectlike composition of separatelyspecified functional concerns in a natural way .
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 7 (2 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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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.