SLAMorris Final Thesis After Corrections.pdf - Cranfield University

thumbnail generation; if a directory is no longer being viewed in the directory
before a file reaches the front of the queue it is removed as it is no longer
required. Therefore visual thumbnails and their associated records are only
created and modified for the directory whilst they are currently required by the
system.
Viewing the files using different methods
An experiment was conducted where 500 JPEG files were copied using the
terminal, from a USB stick to the user’s documents directory. The documents’
directory was then viewed for less than 5 seconds and then closed. The hard
disk was then analysed and less than a fifth of the files (89) within the directory
had associated records within the thumbnail cache. During the experiment only
16 files were seen in the file manager; however the number of records created
in the thumbnail cache was significantly larger than this. A second experiment
repeated the method but left the file manager open for 10 minutes. After the
second experiment there were records in the thumbnail cache for each of the
500 files; 15 of these records were in the fail directory. The results of these
experiments show that when the file browser is used, any file which is eligible to
have a record in the thumbnail cache is added to the thumbnail generation
queue; however files are removed from the queue if the directory is no longer
being viewed in the file browser.
A file is considered eligible when the file type is associated with a method which
utilises the thumbnail cache; the file type is checked and if a thumbnail method
exists for that type then the system uses the method to create or retrieve a
visual thumbnail. Experimentation has shown this can lead to some files within
a directory not added to the thumbnail cache. For example files created in
Microsoft Excel did not create visual thumbnails, without the installation of
additional software.
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