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...GORITHM We start by explaining the intuition behind the algorithm. The key principle that we use is reducing the mapping compilation problem to that of finding exact rewritings of queries using views =-=[21]-=-. 5.1 Intuition Consider the problem of obtaining query views from mapping map = f ◦ g −1 . The view f on C and the view g on S are specified as {V1=QC1, ..., Vn=QCn} and {V1=QS1, ..., Vn=QSn}, respec...

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... views correspond to get, while update and merge views combined define putback. One of our key distinguishing contributions is a technique for propagating updates incrementally using view maintenance =-=[6, 20]-=-, which is critical for practical deployment. Another one is a fundamentally different mechanism for obtaining the views, by compiling them from mappings, which allows describing complex mapping scena...

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...s r : P→S, r ∈ L and p : S→Pwitnessing the equivalence of P and S. As shown in Figure 9, query g partitions S into P ⊆ Pexp × Punexp such that pexp : S→Pexp and punexp : S→Punexp are view complements =-=[2]-=- that together yield p. By condition (ii), g can be rewritten as h ◦ pexp where h is injective. Let h ′ be an exact rewriting of the identity query on Pexp using h, i.e., h ′ reconstructs Pexp from V....

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...pplied to the underlying database. Mapping compilation was explored in IBM’s Clio project, which introduced the problem of generating data transformations from correspondences between schema elements =-=[27]-=-. Our mapping compilation procedure draws on answering queries using views for exact rewritings (surveyed in [21] and examined recently in [18, 29]), and exploits several novel aspects such as the par...

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... views correspond to get, while update and merge views combined define putback. One of our key distinguishing contributions is a technique for propagating updates incrementally using view maintenance =-=[6, 20]-=-, which is critical for practical deployment. Another one is a fundamentally different mechanism for obtaining the views, by compiling them from mappings, which allows describing complex mapping scena...

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...computation of merge views exploits view complements. Recently, researchers have shown rekindled interest in the view update problem. Pierce et al. developed a bidirectional mechanism called ‘lenses’ =-=[7, 16]-=- which uses get and putback functions. Our query views correspond to get, while update and merge views combined define putback. One of our key distinguishing contributions is a technique for propagati...

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...a constraints in S).Asshownin[28], the problem of computing the range of a mapping (or a view, as a special case) can be reduced to that of mapping composition. Composing mappings is very challenging =-=[15, 4]-=-. Due to space constraints, in this paper we only consider the first part of the mapping validation task, checking the injectivity condition. As we show next, this check can be done by exploiting the ...

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...a nullable boolean expression b as (b AND (b IS NOT NULL)) or as (CASE WHEN b THEN True ELSE False END). The final query view produced by the mapping compiler for the scenario of Figure 7 is shown in =-=[5]-=- (there BillingAddr is assumed to be atomic). It illustrates the compound effect of most of the presented techniques. 6. EVALUATION The goal of a client-side mapping layer is to boost the developer’s ...

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...computation of merge views exploits view complements. Recently, researchers have shown rekindled interest in the view update problem. Pierce et al. developed a bidirectional mechanism called ‘lenses’ =-=[7, 16]-=- which uses get and putback functions. Our query views correspond to get, while update and merge views combined define putback. One of our key distinguishing contributions is a technique for propagati...

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...ral views simultaneously. Another line of research focused on closing the underspecification gap. Several mechanisms were suggested in the literature, such as constant complement [2] or dynamic views =-=[17]-=-. So far, this work has turned out to be mostlysof theoretical value, although techniques of [3, 23] appear to have had commercial impact. Our computation of merge views exploits view complements. Rec...

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... Several mechanisms were suggested in the literature, such as constant complement [2] or dynamic views [17]. So far, this work has turned out to be mostlysof theoretical value, although techniques of =-=[3, 23]-=- appear to have had commercial impact. Our computation of merge views exploits view complements. Recently, researchers have shown rekindled interest in the view update problem. Pierce et al. developed...

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...ve and the range constraints of f (i.e., those inferred from f and the schema constraints in C) imply the range constraints of g (i.e., those inferred from g and the schema constraints in S).Asshownin=-=[28]-=-, the problem of computing the range of a mapping (or a view, as a special case) can be reduced to that of mapping composition. Composing mappings is very challenging [15, 4]. Due to space constraints...

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...a constraints in S).Asshownin[28], the problem of computing the range of a mapping (or a view, as a special case) can be reduced to that of mapping composition. Composing mappings is very challenging =-=[15, 4]-=-. Due to space constraints, in this paper we only consider the first part of the mapping validation task, checking the injectivity condition. As we show next, this check can be done by exploiting the ...

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...database and application representations remains a hard problem. Researchers and practitioners attacked it in a number of ways. A checkpoint of these efforts was presented by Carey and DeWitt in 1996 =-=[10]-=-. They outlined why many such attempts, including object-oriented databases and persistent programming languages, did not pan out. They speculated that object-relational databases would dominate in 20...

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...ntity SQL, as can be seen using the construction in the paragraph above. A third alternative is to obtain update views from query views. This requires solving the view update problem. As was shown in =-=[13]-=-, finding a unique update translation for even quite simple (query) views is rarely possible. Therefore, we follow the mapping compilation approach, where query and update views are generated from map...

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...le views. Subsequent research followed two major directions. One line of work focused on determining under what circumstances view updates can be translated unambiguously, more recently for XML views =-=[8]-=-. Unfortunately, there are few such cases; besides, usually every update needs to have a well-defined translation, i.e., rejecting a valid update is unacceptable. Furthermore, in mapping-driven scenar...

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... Several mechanisms were suggested in the literature, such as constant complement [2] or dynamic views [17]. So far, this work has turned out to be mostlysof theoretical value, although techniques of =-=[3, 23]-=- appear to have had commercial impact. Our computation of merge views exploits view complements. Recently, researchers have shown rekindled interest in the view update problem. Pierce et al. developed...

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...ema that do not mention E. Unfolding the update view yields the roundtripping condition E = E − (Q1 − Q2). It holds if and only if Q1 ⊆ Q2, which is undecidable for any relationally complete language =-=[14]-=-. Although it is possible to restrict the query and update views to a subset of Entity SQL for which containment is decidable, writing them by hand is hard and requires significant database expertise....

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...sformations from correspondences between schema elements [27]. Our mapping compilation procedure draws on answering queries using views for exact rewritings (surveyed in [21] and examined recently in =-=[18, 29]-=-), and exploits several novel aspects such as the partitioning scheme, bipartite mappings, and rewriting queries under bidirectional mapping constraints. We are not aware of published work that exploi...

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...pping scenarios in an elegant way. Also, in our approach data reshaping (specified by query and update views) is separated from the update policy (merge views). Further recent work on view updates is =-=[24]-=-, where delta tuples are stored in auxiliary tables if the updates cannot be applied to the underlying database. Mapping compilation was explored in IBM’s Clio project, which introduced the problem of...

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...generation, bookkeeping of tuple provenance, and simplification of views under constraints. The presented approach has been implemented in a commercial product, the Microsoft ADO.NET Entity Framework =-=[1, 11]-=-. A pre-release of the product is available for download. This paper is structured as follows. In Section 2 we give an overview of the Entity Framework. In Section 3 we outline our mapping approach an...

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...sformations from correspondences between schema elements [27]. Our mapping compilation procedure draws on answering queries using views for exact rewritings (surveyed in [21] and examined recently in =-=[18, 29]-=-), and exploits several novel aspects such as the partitioning scheme, bipartite mappings, and rewriting queries under bidirectional mapping constraints. We are not aware of published work that exploi...

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...ject-relational databases would dominate in 2006. Indeed, many of today’s database systems include a built-in object layer that uses a hardwired O/R mapping on top of a conventional relational engine =-=[9, 25]-=-. However, the O/R features offered by these systems appear to be rarely used for storing enterprise data, with the exception of multimedia and spatial data types [19]. Among the reasons are data and ...

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...generation, bookkeeping of tuple provenance, and simplification of views under constraints. The presented approach has been implemented in a commercial product, the Microsoft ADO.NET Entity Framework =-=[1, 11]-=-. A pre-release of the product is available for download. This paper is structured as follows. In Section 2 we give an overview of the Entity Framework. In Section 3 we outline our mapping approach an...

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...xample shortly). Implementing such transformations is difficult, especially since the data usually needs to be updatable, a common requirement for many enterprise applications. A study referred to in =-=[22]-=- found that coding and configuring O/R data access accounts for up to 40% of total project effort. Since the mid 1990’s, client-side data mapping layers have become a popular alternative to handcoding...

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...ject-relational databases would dominate in 2006. Indeed, many of today’s database systems include a built-in object layer that uses a hardwired O/R mapping on top of a conventional relational engine =-=[9, 25]-=-. However, the O/R features offered by these systems appear to be rarely used for storing enterprise data, with the exception of multimedia and spatial data types [19]. Among the reasons are data and ...

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...ndence, the cost of migrating legacy databases, scale-out difficulties when business logic runs inside the database instead of the middle tier, and insufficient integration with programming languages =-=[30]-=-. Database research has contributed many powerful techniques that can be leveraged for supporting mapping-driven data access. And yet, there are significant gaps. Among the most critical ones is suppo...

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...onventional relational engine [9, 25]. However, the O/R features offered by these systems appear to be rarely used for storing enterprise data, with the exception of multimedia and spatial data types =-=[19]-=-. Among the reasons are data and vendor independence, the cost of migrating legacy databases, scale-out difficulties when business logic runs inside the database instead of the middle tier, and insuff...