Efficient recursive XML query processing using relational database systems

A Tale of Two Approaches: Query Performance Study of XML Storage Strategies in Relational Databases

“…Although our effort in [12] asserts that it is indeed possible for a schema-oblivious approach to outperform the schema-conscious approach, it was demonstrated only for recursive XML queries. Naturally, we would like to know whether this result holds for non-recursive XML queries.…”

“…However, it does raise the question whether there exists a schema-oblivious approach in the literature that can outperform XParent significantly and consequently outperform a schema-conscious approach? In [12], we provided answer to this question by presenting a novel schema-oblivious approach called Sucxent++ (Schema Unconscious XML Enabled System) that outperforms XParent by up to 15 times and a schema-conscious approach (Shared-Inlining) by up to 8 times for certain types of recursive XML queries. A recursive XML query is an XML query which contains the descendant axis (//) [10].…”

“…This approach does not require existence of an XML schema/DTD. Some examples of schema-oblivious approaches are Edge approach [7], XRel [18], XParent [8], Sucxent++ [12]. The schema-conscious method, on the other hand, derives a relational schema based on the DTD/XML schema of the XML documents.…”

“…In particular, we compare the performance of one schema-conscious approach (Shared-Inlining [15]) with two representative schema-oblivious approaches (XParent [8] and Sucxent++ [12]). At this point, one would question the justification of this work as a growing body of research suggests that schema-conscious approaches perform better than schema-oblivious approaches.…”

“…This approach either shred the XML documents into relational tables using some sort of encoding scheme [1,5,7,8,12,15,18,19] or use a BLOB column to store the XML document [6,20,21]. BLOB-based approaches use stored procedures to invoke an external XPath/XQuery processor.…”