T. Griffin, L. Libkin, Incremental Maintenance of Views with Duplicates, SIGMOD Conf., San Jose, 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....work on relational view maintenance [3, 10, 5] when considering rather simple views took an algorithmic approach, that is, they propose a fixed procedure to compute the changes to the view given the changes to the base relations. Later efforts on more complex view definitions including duplicates [8] or aggregations [19, 16] and also object oriented views [2] often have instead taken an algebraic approach. Unnesting and restructuring of data is core even in the simplest XQuery view definitions due to the nested structure of XML data. Thus any practical solution for XQuery views should support ....

....unnesting, aggregation and tagging. The algebraic approach, illustrated in Figure 3, is therefore the appropriate foundation for tackling incremental view maintenance in the XML context. Definition Figure 3: Illustration of algebraic approach to XML view maintenance As pointed out in [8], the main advantages of an algebraic approach to view maintenance include: It is independent from the view definition language syntax. This is critical for XML given that XQuery is still a working draft, and changes to its syntax are likely to occur. Experience with SQL also has shown that even ....

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T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In $IGMOD, pages 328-339, 1995.

....view is based, change, the materialized view has to be updated too. The incremental approach, differently from the complete recomputation, aims to reuse the previous contents by computing only the delta, namely new tuples to be added and to be deleted. Many works on incremental view maintenance [5, 9, 12, 19] do not apply in a multi source environment because they deal with views and tables in the same source. In fact, in a multi source environment a view can be defined on remote base tables belonging to different data sources, possibly autonomous, and the view can be in a different site with respect ....

....set of states. Each maintenance query is derived by using change propagation rules that basically transform the query expression of the view in order to minimize costs of computing the tuples to be added to and deleted. Change propagation rules for centralized database has been identified by [9, 19]. These rules work correctly only in pre update state and without concurrency, namely within the same transaction generating the changes. As it will be shown in subsection 5.3 these rules have been improved by [5] in order to work also in post update state using a distinct transaction. However it ....

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T. Griffin, L. Libkin. Incremental maintenance of views with duplicates. In proceedings of SIGMOD, pages 328-339, May 1995

....During updates the materialized set is reconciled and the most beneficial subset of it is refreshed within a given maintenance window. A critical performance issue is how fast we can incorporate the updates to the views. Efficient computation of the views using techniques like [Gupta et al. 1993; Griffin and Libkin 1995; Jagadish et al. 1995; Agrawal et al. 1996; Harinarayan et al. 1996; Mumick et al. 1997; Zhao et al. 1997] and or bulk incremental updates [O Neil et al. 1996; Roussopoulos et al. 1997; Jermaine et al. 1999] enhances the overall performance of the system. In DynaMat any of these techniques can be ....

....views. Several methods have been proposed [Agrawal et al. 1996; Deshpande et al. 1996; Sarawagi et al. 1996; Ross and Srivastava 1997; Zhao et al. 1997] for fast (re) computation of data cube aggregates. On the other hand, incremental maintenance algorithms have been presented [Gupta et al. 1993; Griffin and Libkin 1995; Jagadish et al. 1995; Mumick et al. 1997; Roussopoulos et al. 1997] that handle grouping and aggregation queries. For our framework, we assume that the sources provide the differentials (called deltas) of the base data, or at least the log files are available. If this is the case, then an ....

Griffin, T. and Libkin, L. 1995. Incremental Maintenance of Views with Duplicates. In Proceedings of the ACM SIGMOD Conference (San Jose, CA, May 1995), pp. 328--339.

....retain the currency of the data warehouse. This requires maintenance of complicated views which is an exceedingly costly problem. The maintenance of view is often done, for reasons of efficiency, using incremental techniques rather than recomputing the view from scratch. There has been some work [1, 3, 5, 7, 8, 9, 10, 16, 17, 24, 25] in maintenance of views and most of the current work revolves around direct manipulation (incrementally) of auxiliary relations [10, 15, 16, 18] in order to improve the efficiency of view maintenance. These auxiliary relations are derived from the intermediate results of the view computation. In ....

....R i are foreign key attributes and R i joins on a foreign key attribute joins with other relation, say R j , and updates to R i are made, then the updates to the view will be empty. 7 A Simple Analysis 8 Related Work The view maintenance problem has been studied by many researchers in general [1, 2, 3, 5, 6, 7, 8, 9, 10, 12, 13, 16, 17, 18, 19, 20, 21, 23, 25]. The recent survey of view maintenance literature can be found in [8] In all papers, except [18] views are defined as a subset of relational algebraic expressions, i.e. SPJ views, views with grouping aggregation. In [18] the authors have proposed an exhaustive enumerative algorithm for ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. ACM SIGMOD Int. Conf. on Management of Data, 1995.

....experimental results show that recomputation of the view is generally preferable to incremental maintenance, so the order of incremental propagation is not relevant. An alternative approach for computing differentials is to generate the entire differential expression, and optimize it (see, e.g. [6]) However, the resultant expression can be very large exponential in the size of the view expression. Optimizing such large expressions can be quite expensive, since query optimization is exponential in the size of the expression. Moreover, creating differential expressions is difficult with ....

....the size of the view expression. Optimizing such large expressions can be quite expensive, since query optimization is exponential in the size of the expression. Moreover, creating differential expressions is difficult with more complex expressions containing operations other than join (see, e.g. [6]) In contrast, the process of propagating differentials can be expressed purely in terms of how to compute the differentials for individual operations, given the differential of their inputs. As a result it is also easy to extend the technique to new operations. 4.2 The Query DAG Representation ....

GRIFFIN, T., AND LIBKIN, L. Incremental maintenance of views with duplicates. In ACM SIGMOD Intl. Conf. on Management of Data (1995).

....semantics is that duplicate elimination is a rather expensive operation and, for efficiency, is not enforced, unless specifically requested by the user. There is some Chapter 1. Introduction 9 work related to multisets for the Datalog model [GKM92, GMS93, Ana96, AV95] and the relational model [GL95] In this thesis, we use, and build on, the change propagation expressions proposed by Griffin and Libkin [GL95] for a multiset al..gebra. 1.6 Thesis Outline Here is the outline of the rest of this thesis: Chapter 2: We present a detailed discussion of previous work on incremental view ....

....unless specifically requested by the user. There is some Chapter 1. Introduction 9 work related to multisets for the Datalog model [GKM92, GMS93, Ana96, AV95] and the relational model [GL95] In this thesis, we use, and build on, the change propagation expressions proposed by Griffin and Libkin [GL95] for a multiset al..gebra. 1.6 Thesis Outline Here is the outline of the rest of this thesis: Chapter 2: We present a detailed discussion of previous work on incremental view maintenance and related research. We concentrate on incremental algorithms for view maintenance as well as applications ....

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T. Griffin and L. Libkin. Incremental Maintenance of Views with Duplicates. In Proceeding of ACM-SIGMOD Conference on Management of Data, pages 328--339, 1995.

....should be reflected in views defined in terms of these relations. Production rules derived from an analysis of the view definition can be used to determine changes to views [148, 149] As recomputing views can be expensive, several incremental methods for view maintenance have been proposed [15, 53, 141]. View redefinition refers to a change in a view definition; the usual way to update a view upon redefinition is to compute the new view from scratch; a more efficient alternative may be to exploit existing views through view adaptation [54] 38 4.3 The Dye View Definition Language Dye is a ....

....by efficient incremental modifications. A more recent version of this approach is to generate production rules from view specifications [148, 149] production rules are typically implemented as Event Condition Action rules [93] Related incremental view maintenance techniques are also described in [15, 53, 141]. 4.5.1 Materializing Views from Scratch In order to generate a program to materialize a view from scratch, we begin by creating a view parse graph from the declarative view specification. The vertices in the parse graph correspond to the constants, attributes, sets, and operations ....

T. Griffin and L. Libkin. Incremental Maintenance of Views with Duplicates. ACM SIGMOD Record, 24(2):328--339, June 1995.

....will be judged appropriate, but several have been proposed. See, e.g. MSVT94] See [PI97] for a brief summary of proposed models and references. In the context of databases, there is by now substantial literature on dynamic query evaluation, a.k.a. incremental view maintenance (see, e.g. [BLT86, QW91, DS93, GMS93, PI97, DS95, GL95, GM95, Via97, DS97a]) Much of this work (e.g. GMS93] is concerned with efficiently recomputing views when the query itself is expressible in a restricted language, such as SQL. In this paper our concern is somewhat different. The goal is to evaluate various queries which aren t necessarily expressible statically ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. ACM SIGMOD, 1995.

....at view definition time, but at the same time detects a wider class of SM updates by using the view instance. In this paper we adopt a similar approach to that in [15, 14] We also note that several paper have also addressed the general problem of updating views when source data is available [2, 3, 4, 7, 9, 13, 20, 23] 3 Preliminaries 3.1 Definitions and Assumptions In this paper we adopt a DATALOG framework to present our results in a similar fashion to that in [15] though this is not essential to our results . The views we consider are conjunctive queries defined by: Q : v( X 0 ; U 0 ; Z 0 ) ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. ACM SIGMOD Conference, pages 328--339, 1995.

....Maintainer first computes the deltas for the derived views using a predefined set of queries called maintenance expressions, and then it installs these deltas into the derived views. The maintenance expressions of views defined using SQL SFW statements (without subqueries) are well studied, e.g. [5], and we do not discuss them here. For views defined using SFWG statements (i.e. views with GROUP BY and aggregation) we introduce and contrast four different maintenance algorithms through a comprehensive example. In this example, let us suppose that view V 1 contains the tuples shown in Table ....

....the summary delta to the aggregate view. In this paper, we have presented three possible implementations of the view maintenance procedure, and evaluated their performance through experiments. Reference [7] assumes that materialized views use the cnt representation. On the other hand, reference [5] assumes the dup representation. To our knowledge, our paper is the first to investigate in detail the pros and cons of the two representations for view maintenance, and to present supporting experiments. We also briefly described the WHIPS system. Although significant research has been devoted ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. of the 1995 ACM SIGMOD Intl. Conf. on Management of Data, pages 328--339, May 1995.

....to the warehouse. Clearly if naive re computation is assumed for refreshing materialized views, then the number of views will be minimum and this will lessen the value of DynaMat. On the other hand, efficient computation of these views using techniques like [AAD 96, HRU96, ZDN97, GMS93, GL95, JMS95, MQM97] and or bulk incremental updates [RKR97] tremendously enhances the overall performance of the system. In DynaMat any of these techniques can be applied. In section 2.4.2 we propose a novel algorithm that based on the goodness measure, computes an update plan for the data stored in ....

....the properties of the data sources and the aggregate functions that are being computed by the views. Several methods have been proposed [AAD 96, HRU96, ZDN97] for fast (re) computation of Data Cube aggregates. On the other hand, incremental maintenance algorithms have been presented [GMS93, GL95, JMS95, MQM97, RKR97] that handle grouping and aggregation queries. For our framework, we assume that the sources provide the differentials of the base data, or at least the log files are available. If this is the case, then an incremental update policy can be used to refresh the pool. In this ....

T. Griffin and L. Libkin. Incremental Maintenance of Views with Duplicates. In Proceedings of the ACMSIGMOD, pages 328--339, San Jose, CA, May 1995.

....to the changes in the source data is referred to as View Maintenance. Refreshing the warehouse data is often done, for reasons of efficiency, using incremental techniques rather than recomputing the view from scratch. There has been significant research on view maintenance in traditional databases [8, 12, 17, 23 25, 47, 50, 51] and in data warehouses [4, 29, 30, 44, 57, 58] In data warehousing, the view maintenance has branched into a number of sub problems such as self maintenance, consistency maintenance, update filtering and on line view maintenance. We investigate these issues and propose new ways of looking at ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. ACM SIGMOD Int. Conf. on Management of Data, 1995.

.... view defined by set differences [BM95b] View indexing by means of pointer structures has been described in [Baek95] BM95a] BM95b] BM95c] JMR91] QW91] Rou82a] Rou82b] Rou91] RK91] Val87] The use and refreshment of materialized views has been de2 scribed in [BM90] CKPS95] GL95] GMR95] HK95] Han87] LMSS95] SJGP90] SR87] ZGMHW95] Incremental techniques has been described for active databases [CSL 90] CW91] HCKW90] Han92] RCBB89] WDSY91] for deductive databases [GMS93] and for temporal databases [BM95c] JMR91] McK88] However, we are not ....

T. Griffin and L. Libkin. Incremental Maintenance of Views with Duplicates. In Proceedings of the 1995 ACM SIGMOD International Conference on Management of Data, San Jose, California, USA, 1995.

.... survey on strategies for view maintenance is given in [11] The basic idea of most strategies is to update the views incrementally by using the (relatively small) change to the base relations, as well as the base relations and the old views themselves, to derive the change to the views (e.g. [1, 16, 21, 7, 10, 8, 6, 5]) More advanced strategies use auxiliary data structures to help the process. The tagging strategy reported in this paper falls into this category. Other auxiliary data structures adopted by view maintenance strategies include [1, 21, 10] using counters and [18] using pointers. These strategies ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proc. ACM SIGMOD Int. Conf. on Management of Data, 1995.

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T. Griffin, L. Libkin, Incremental maintenance of views with duplicates, In SIGMOD '95, pages 319--330.

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T. Griffin, L. Libkin, Incremental maintenance of views with duplicates, in "Proceedings of ACM-SIGMOD International Conference on Management of Data," San Jose, CA, May 1995.

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T. Griffin, L. Libkin, "Incremental maintenance of views with duplicates," in "Proceedings of ACM-SIGMOD International Conference on Management of Data," San Jose, CA, May 1995.

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T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. Proceedings of the 1995.

....it suffices to show that g(o) Z i = Y i for all i. The base case is the same as in Lemma 4. Now assume g(o) Z i = Y i and prove g(o) Z i 1 = Y i 1 . First note that all Z j s are subbags of g(o) From this, using the equations for reasoning about the equivalence of bag expressions from [6], calculate g(o) Z i 1 = g(o) Z i : f 0 (o; Z i ) by definition of dfp = g(o) Z i : f(o; g(o) Z i ) by definition of f 0 = g(o) Z i : f(o; Y i ) by the hypothesis = g(o) Z i ) Z i minf(o; Y i ) Z i : g(o) by (P8) of [6, p. 333] g(o) ....

....of [6, p. 333] g(o) Z i ) Z i minf(o; Y i ) since Z i g(o) On the other hand, Y i 1 = Y i ] f(o; Y i ) ming(o) by definition of bfp = g(o) Z i ) f(o; Y i ) min g(o) by the hypothesis = g(o) Z i ) ming(o) f(o; Y i ) min(g(o) g(o) Z i ) by (P12) of [6] = g(o) Z i ) Z i minf(o; Y i ) since Z i g(o) which proves the lemma. Using these lemmas, one can show by a straightforward induction argument, that bfp is expressible in BQL(dfp) and vice versa, thus proving Theorem 3(a) We now sketch the proof of Theorem 3(b) Let dfp set f;g ....

T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In Proceedings ACM SIGMOD, 1995, pages 328--339.

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T. Griffin, L. Libkin, Incremental Maintenance of Views with Duplicates, SIGMOD Conf., San Jose, 1995.

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T. Gri#n and L. Libkin. Incremental maintenance of views with duplicates. In Proceedings of the 1995.

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T. Griffin and L. Libkin, Incremental maintenance of views with duplicates. In SIGMOD'95, pages 328-339, May 1995.

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T. Gri#n and L. Libkin. Incremental maintenance of views with duplicates. In M. J. Carey and D. A. Schneider, editors, Proceedings of the 1995.

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T. Gri#n, L. Libkin, Incremental maintenance of views with duplicates, in: Proc. SIGMOD, 1995, pp. 328-- 339.

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T. Griffin and L. Libkin. Incremental maintenance of views with duplicates. In ACM SIGMOD Conference, pages 328--339, 1995.

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