Processing OODB queries by O-Algebra

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Abstract
O-Algebra is an object,algebra,designed,for processing,Object- Oriented,Database,(OODB) queries.,We present,the,concept of internal type objects, which are uniform and represent the front-end,objects.,O-Algebra is an,algebra,whose,operands,are collections,of internal,objects.,Due,to uniform,operands,and simple operators defined in O-Algebra, a small yet powerful set of O-Algebra laws can be obtained, which is important for query,optimization,by algebraic,rewriting.,After presenting,O- Algebra, we introduce an approach to transform OQL queries to O-Algebra queries.,Since O-Algebra operations,do not,have complex arguments, the nested queries of OQL can be reduced by a general,method,after they are transformed,t o O-Algebra queries. Compared to other approaches of reducing nested queries, this approach,k,more,general,because,it is not,restricted,by,the patterns,of nested,queries. 1,Introduction OODB query languages, such as OQL [Ca94], are usually converted,to,some,internal,representations,for,being,op- timized,and,implemented,efficiently.,Object,algebras,are such,internal,representations.,The,existing,object,alge- bras,can,be,classified,into,two,categories:,the,complex,ob- ject,algebras,and,the,simple,object,algebras.,The,main factor,distinguishing,them,is that,the,complex,object,al- gebras allow complex arguments in operations (i.e., argu- ments can be paths, or even subexpressions), while the simple object algebras don’t. For example, consider a query,finding,all the,companies,with,a zipcode,44106. For the object algebra EQUAL [SZ90], an algebraic expres- sion can be select(Companies, Jc, c.address.zipcode=44106), where,the,select,predicate,‘c. address,.zipcode=441 06’ is the complex,argument,of the,select,operator,which,contains

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