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XML has become an important medium for data exchange, and is frequently used as an interface to – i.e. a view of – a relational database. Although much attention has been paid to the problem of querying relational databases through XML views, the problem of updating relational databases through XML views has not been addressed. In this paper we inv...
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... However, query trees were conceived as an internal query representation and are not well-suited for end-users. To specify how an XML view is constructed from a relational source, we therefore use the UXQuery [11] view definition language. UXQuery is expressive enough to capture the XML views that we have encountered in practice yet is simple to understand and manipulate. ...
... The XML view resulting from this example query is as follows: The need for a way of specifying groups in XQuery has been extensively discussed over the past few years. Following our xnest proposal in 2003 [11], the groupby operator was proposed in 2004 [25, 26]. They propose an algorithm that translates XQuery queries using pure XQuery syntax into equivalent queries that use groupby. ...
... A subset of XQuery to specify XML views over relational databases We have proposed and implemented a subset of XQuery which is capable of constructing XML views over relational databases [11]. UXQuery uses query trees as an intermediate representation to map the resulting XML view to relational views. ...
XML has become an important medium for data exchange, and is frequently used as an interface to (i.e., a view of) a relational database. Although a lot of work has been done on querying relational databases through XML views, the problem of updating relational databases through XML views has not received much attention. In this work, we map XML views expressed using a subset of XQuery to a corresponding set of relational views. Thus, we transform the problem of updating relational databases through XML views into a classical problem of updating relational databases through relational views. We then show how updates on the XML view are mapped to updates on the corresponding relational views. Existing work on updating relational views can then be leveraged to determine whether or not the relational views are updatable with respect to the relational updates, and if so, to translate the updates to the underlying relational database.
... In previous work [2], we have proposed PATAXÓ, an approach to update relational databases through XML views. In this approach, XML views are constructed using UXQuery [1], an extension of XQuery, and updates are issued through a very simple update language. The scenario we address in this paper is different in the following senses: (i) In PATAXÓ [2], updates are issued through an update language that allows insertions, deletions and modifications. ...
... To do so, it uses an existing approach on updates through relational views [7]. Basically, a view query definition expressed in UXQuery [1] is internally mapped to a query tree [2]. Query trees are a formalism that captures the structure and the source of each XML element/attribute of the XML view, together with the restrictions applied to build the view. ...
In this paper, we focus on B2B scenarios where XML views are ex- tracted from relational databases and sent over the Web to another application that edits them and sends them back after a certain (usually long) period of time. In such transactions, it is unrealistic to lock the base tupl es that are in the view to achieve concurrency control. Thus, there are some issues that need to be solved: first, to identify what changes were made in the view and secon d, to identify and solve conflicts that may arise due to changes in the database s tate during the trans- action. We address both of these issues in this paper by proposing an approach that uses our XML view update system PATAXÓ.
... Query trees represent an intermediate query form, and any (subset of an) XML query language that can be mapped to this form could be used as the top-level language. In particular, we have implemented our approach in a system called Pataxó that uses a subset of XQuery to build the XML views and translates XQuery expressions into query trees as an intermediate representation [Braganholo et al. 2003b]. Since we use relational views in our solution, we are limited to the cases where it is possible to update those relational views. ...
... This work has resulted in a number of scientific publications. The main ones are, Braganholo et al. 2003b, Braganholo et al. 2003a . Two related papers were also published in IIWAS 2001 and WTDBD 2002. ...
... Two related papers were also published in IIWAS 2001 and WTDBD 2002. The SBBD paper [Braganholo et al. 2003b] was nominated to the best paper award in 2003. Additionally, four undergraduate projects resulting from this work were supervised by Carlos Heuser and Vanessa Braganholo. ...
Although a lot of work has been done on querying relational databases through XML views, the problem of updating relational databases through XML views has not received much attention. In this work, we present a solution to the XML update problem which uses query trees as the view defini-tion language, and maps XML views to a set of corresponding relational views. In this way, we transform the problem of updating relational databases through XML views into the classical problem of updates through relational views.
... The problem with this approach is automation: a user has to programmatically define the view instead of just defining its schema. MIX [2] and UXQuery [29] follow this approach, the former using its own query language (XMAS) and the latter using a subset of the XQuery language. ...
This technical report describes the XML data integration framework being built within the AutoMed heterogeneous data integration system. It presents a description of the overall framework, as well as an overview of and comparison with related work and solutions by other researchers. The contributions of this research are the development of two algorithms for XML data integration, the first for schema integration and the second for view materialization, both based on graph restructuring.
... Second, they are easy to understand yet expressive enough to capture several important aspects of XQuery such as nesting, composed attributes , and heterogeneous sets. 1 They can therefore be thought of as the intermediate processing form for a subset of many different XML query languages. For example, we have developed an implementation of our technique which uses a subset of XQuery as the top-level language [6]. After defining query trees, we introduce a notion which will be used to describe the mapping to relational queries, the abstract type of a query tree node. ...
... Query trees rep-resent an intermediate query form, and any (subset of an) XML query language that can be mapped to this form could be used as the top level language. In particular, we have implemented our approach in a system called Pataxó that uses a subset of XQuery to build the XML views and translates XQuery expressions into query trees as an intermediate rep- resentation [6]. Similarly, our update language represents an intermediate form that could be mapped into from a number of high-level XML update languages (using a static evaluation of which updates are to be performed). ...
This paper addresses the question of updating rela- tional databases through XML views. Using query trees to capture the notions of selection, projection, nesting, grouping, and heterogeneous sets found throughout most XML query languages, we show how XML views expressed using query trees can be mapped to a set of corresponding relational views. We then show how updates on the XML view are mapped to updates on the corresponding relational views. Existing work on updating rela- tional views can then be leveraged to determine whether or not the relational views are updatable with respect to the relational updates, and if so, to translate the updates to the underlying relational database.
Querying XML effectively and efficiently using declarative languages such as XQuery and XPath has been widely studied in both academic and industrial settings. Most RDBMS vendors now support XML as a native data type with SQL/XML and XQuery support over it. However, the problem of updating XML is still the subject of ongoing effort. Several SQL/XML update extensions have been implemented and an XQuery Update Facility is in the proposal phase to add an update capability to XQuery. There are a lot of challenges involved in updating XML, particularly identifying and updating partial fragments of XML while maintaining concurrency, transactional semantics and validity of the document. In this paper, we illustrate the XML update functionality provided by Oracle XML DB within the context of SQL/XML. This functionality has been developed and optimized based on actual customer use cases of querying and updating XML. We discuss our design philosophy, optimization details for providing capability of updating XML and compare it with the current XQuery Update Facility proposal with the goal of providing insight into incorporating the XQuery Update Facility in the SQL/XML standard in the future.
