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Examples of star twig queries  

Examples of star twig queries  

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Conference Paper
Full-text available
Despite a large body of work on xml twig query processing in relational environment, systematic study of xml join evaluation has received little attention in the literature. In this paper, we propose a novel and non-traditional technique for fast evaluation of multi-source star twig queries in a path materialization-based rdbms. A multi-source star...

Contexts in source publication

Context 1
... (www.ebi.ac.uk/embl/)), then XQuery can be used to formulate meaningful queries over these data sources. Figure 1 shows three example queries. Observe that Q 1 , Q 2 , and Q 3 correlate four, three, and two data sources, re- spectively. ...
Context 2
... in a multi-source star twig query all join expressions share a common document source and hence forms a star-shaped query graph. For example, queries in Figure 1 are examples of star twig queries. Formally, it is defined as follows. ...
Context 3
... absolute path expression of r is de- noted by r.absExp. For example, consider r = ($entry, "/name") in Q 2 (Figure 1). Then r.absExp is "/uniprot/entry/name" as $entry is bound to the expression "/uniprot/entry". ...
Context 4
... features of these datasets are given in Figure 2(a). We chose eight multi-source star twig queries as shown in Figures 1 and 3 that join up to four data sources, and have between three to nine expressions in the where clause. We transform these queries to our model (Section 3) if necessary. ...

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Citations

Article
Despite a large body of work on XML twig query processing in relational environment, systematic study of XML join evaluation has received little attention in the literature. In this paper, we propose a novel and non-traditional technique for fast evaluation of multi-source star twig queries in a path materialization-based RDBMS. A multi-source star twig joins different XML documents on values in their nodes and the XQuery graph takes a star-shaped structure. Such queries are prevalent in several domains such as life sciences. Rather than following the conventional approach of generating one huge complex SQL query from a twig query, we translate a star query into a list of SQL sub-queries that only materializes minimal information of underlying XML subtrees as intermediate results. We have implemented this scheme on top of a path materialization-based XML storage system called SUCXENT++. Experiments carried out confirm that our proposed approach built on top of an off-the-shelf commercial RDBMS has excellent real-world performance.