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Tomasz Pieciukiewicz, Kazimierz Subieta
Recursive Query Processing in SBQL
979
Abstract
Recursive queries are required for many tasks of database
applications. Among them we can mention Bill-Of-Material (BOM), various
kinds of networks (transportation, telecommunication, etc.), processing
semi-structured data (XML, RDF), and so on. The support for recursive
queries in current query languages is limited and lacks of theoretical
foundations. In particular, this concerns corresponding extensions of SQL in
Oracle and DB2 systems. In this report we present recursive query processing
capabilities for the object-oriented Stack-Based Query Language (SBQL) and
compare them with similar capabilities in variants of SQL. SBQL offers very
powerful and flexible recursive querying capabilities due to the fact that
recursive processing operators are fully orthogonal to other features of
this language. This report specifies corresponding SBQL constructs, such as
transitive closures and fixed point equations. We compare them to other
query languages, in particular to Datalog. We also present briefly
optimization possibilities for recursive queries.
Keywords: Stack-Based Approach (SBA), query languages, SBQL,
object-orientedness, transitive closures, fixed-point equations, deductive
rules, recursive functions, recursive views
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