| Summary: | 碩士 === 國立中興大學 === 資訊科學學系 === 86 === Providing the functionality of object version is essential to
object-orienteddatabase systems. In this study we propose a new
object version model, whichenhances the existing version models
and provides more operations for users to use the functionality
conveniently. This version model uses a new representation
scheme to avoid the waste of storage space for large objects.At
the same time, it can process regular objects,large objects and
compositeobjects efficiently. We have implemented the proposed
version model in CTSS(Chao Ta Storage System), which is a
storage system developed by the database laboratory of National
Chao Tung University. From this implementation, we have
verifiedthe feasibility of this version model. The model is
designed as an independent module, which can be easily plugged
into CTSS or other object storage systems with a minor
modification of some of its module interfaces. To understand
the advantages and disadvantages of our model over others, we
review the characteristics of various version models and then
compare these models with ours. Since large objects in our model
are stored in version difference, a fair amount of space saving
can be expected. We analyze the space saving for each different
data update ratio, and observe that, if the updatedata size is
about 30% of the original object version and there are 10
regionsupdated, then there is at least69.7% of space saving.On
the other hand, when we retrieve a regular or evaluated object
version by its OID, the retrieving time is identical that needed
for a non-versionable object.
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