Usable Recursive Queries

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 semistructured data (XML, RDF), and so on. The support for recursive queries in current query languages is limited. In particular, this concerns corresponding extensions of SQL in Oracle and DB2 systems. In this paper we present recursive query processing capabilities for the object-oriented Stack-Based Query Language (SBQL). SBQL offers very powerful and flexible recursive querying capabilities due to the fact that recursive processing operators are fully orthogonal to other capabilities of this language. The presented features aim at the ease of recursive programming in databases and not at building new theoretical foundations. This paper discusses novel SBQL constructs, such as transitive closures, fixed point equations and recursive procedures/views. Their main advantage is that they are seamlessly integrated with object-oriented facilities, computer environment and databases.