CIS 644 Thurs Oct. 21, 1999 W9B

1
CIS 644 Thurs Oct. 21, 1999 W9B
active objects DM classes
2

Exam1 covers class scenario
models open book (will the book help??)
Tues Nov 2. on campus in class off
campus sent by email
email or fax it back

3
concurrent systems logically
simultaneous real-time systems reactive
systems multi-user systems layered
systems very subtle problems dead-lock
corrupted data x x1
4
history 1967 Simula classes, objects
1980 Smalltalk80 ??? semaphores
1975 Brinch Hansen, monitors 1982 Ada
tasks w rendezvous, time-out
1995 Java threads, sync
5
UML static models class model
object model . no so useful dynamic models
use-case p237 activity diagrams
sequence (scenario)
collaboration p. 249 state models
activity (petri net) p. 257, 266
state chart (Harel) p. 331
6
UML Chap 22 active class .. p.
311 active object process (heavyweight)
thread (lightweight)
7
communication between objects OO vocabulary
messages signals ( events,
exceptions) 1. passive to passive 2. active
to active a) rendezvous p. 314
b) mailbox 3. active to passive 4.
passive to active
8
critical regions atomic actions UML 1)
sequential (no threads) 2) guarded 3)
concurrent Java synchronized p. 316
9
Chap 4 multiple UI s each owns one
terminal device Video store are
there any thread conflicts?? what methods
synced Airline reservations same.
10
End