Information Technology Reference
In-Depth Information
(6)
The behaviour of each lecture ambient (named after the lecture's id
lectid
) in the cache is
modelled by the following process:
(7)
The InfoStation will act as follows. First, it receives a request from
, then it checks
the availability of the lecture in its cache by sending a request to the
ℎ
ambient, i.e.
!
↓(,,,).ℎ
↓〈,,,〉.0
(8)
If the cache replies with the content of the lecture, it will send a request to the InfoStation
Centre with a flag set to 1 (meaning that the requested lecture exists in its cache) asking
whether the user is currently taking a mTest. If the user is taking a mTest, then the mLecture
service request must be denied. If the cache did reply with NULL as lecture's content, then
the infostation will send a request to the InfoStation Centre with the flag set to 0 (meaning
that the lecture does not exist in its cache) asking for both the requested lecture and to check
whether the user is taking a mTest. This behaviour of the IS is modelled as:
(9)
where C and N are de_ned as follows:
