Relational databases have proved inadequate for supporting new classes of
applications, and as a consequence, a number of new approaches have been taken
(Blaha 1998), (Harrington 2000). The most salient alternatives are denormalisation
and conversion to an object-oriented database (Douglas 1997). Denormalisation
can provide better performance but has deficiencies with respect to
data modelling. Object-oriented databases can provide increased performance
efficiency but without the deficiencies in data modelling (Blaha 2000).
Although there have been various benchmark tests reported, none of these
tests have compared normalised, object oriented and de-normalised databases.
This research shows that a non-normalised database for data containing type
code complexity would be normalised in the process of conversion to an objectoriented
database. This helps to correct badly organised data and so gives the
performance benefits of de-normalisation while improving data modelling.
The costs of conversion from relational databases to object oriented databases
were also examined. Costs were based on published benchmark tests, a
benchmark carried out during this study and case studies. The benchmark tests
were based on an engineering database benchmark. Engineering problems such as
computer-aided design and manufacturing have much to gain from conversion to
object-oriented databases. Costs were calculated for coding and development, and
also for operation. It was found that conversion to an object-oriented database was
not usually cost effective as many of the performance benefits could be achieved
by the far cheaper process of de-normalisation, or by using the performance
improving facilities provided by many relational database systems such as
indexing or partitioning or by simply upgrading the system hardware.
It is concluded therefore that while object oriented databases are a better
alternative for databases built from scratch, the conversion of a legacy relational
database to an object oriented database is not necessarily cost effective.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.