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Some information will be persistant information in the Fido database. Other
information will be marked as volitile, because it is constantly changing.
Such as: Stock quotes, the time, and the weather. This information can
be retrieved on-demand from the web with the use of Web Services.
Information marked as volitile in the Fido database will be retrieved upon each
query. This type of information will have a specified WebService that provides
the information. Also, the information will have a time that the information
becomes stale. As such, if the information becomes stale, it must be refreshed
from the WebService or is marked as unreliable. Each piece of volitile information
will contain the WebService that updates it.
Also, a time will be included with the information on the average time for
a lookup. This will be timeout value that allows different information sources
to have different access times.
The above two numbers will be used as follows: The user wants a piece of
volitile information, such as the current temperature. The current piece of
information is marked as stale, so the system attempts to ask a web service
for the information. The timeout value will specifiy that site may be down
or busy, and reports this to the user. The user may know the network is slow
today and ask the system to continue to try. The stale value will say that
the current temperature probably will not change in the next five minutes.
If another person asks the system for the current temperature, the system
will not need to refresh the data over the network.
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