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OODBObject Oriented Data Base
OODBObject-Oriented Database
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Section 7 presents transformation rules for unnesting OODB queries.
which is based on our example OODB schema, is a valid expression in the calculus.
We use both a calculus and an algebra as intermediate forms because the calculus closely resembles current OODB languages and is easy to normalize, while the algebra is lower-level and can be directly translated into the execution algorithms supported by database systems.
There are many recent proposals for OODB query optimization that focus on unnesting nested queries (also known as query decorrelation) [Cluet and Moerkotte 1995a; 1995b; Claussen et al.
Since OODB queries are far more complex than relational ones, it is even more crucial to express the unnesting transformations in a formal algebra that will allow us to prove the soundness and completeness of these transformations.
Second, our unnesting algorithm is more concise, more uniform, and more general than earlier work, mostly due to the use of the monoid comprehension calculus as an intermediate form for OODB queries.
These synchronous cooperation modes require extensions to the hypermedia system to support shared commitment of changes to the OODB.
For example, we have implemented run-time client processes on an Apple Macintosh communicating with an OODB server on Unix via TCP/IP.
The data objects may be stored by the editors in separate files outside the OODB or the editors may use the OODB.
The RP is a server that communicates with the editors and it is a client of the OODB server.
The OODB server and the RPs may run on different computers in a distributed environment.
Technically such coordination is supported through event notifications distributed by the OODB server.