UML Tutorials
State Diagrams / Pseudostates: Fork & Join
Visitors to VTC.com will be able to view all introductory videos for each training course.
Free Trial Members will gain access to first three chapters for each training course.
Full Access Members have full access to VTC.com�s entire library of video tutorials.
Learn More
Subtitles of the Movie (UML / State Diagrams / Pseudostates: Fork & Join)
You'll find forks and joins in both state diagrams and in activity diagrams. In activity diagrams forks and joins are called nodes. In state diagrams forks and joins are considered pseudo states and that's because they are not an actual state of the object, rather there is something that has to happen during a transition for the object to move from one state to the next. Forks and joins are represented by black bar and these can either be vertical as they are here or horizontal with one transition coming in and one or more going out if you're dealing with a fork. If you're dealing with a join you have two or more transitions coming in and one transition going out. And as an activity diagrams in a join both of these states have to be present before you can move on to the next state. This is the same orthogonal composite state that we were looking at in a different movie for a burglar alarm system the intrusion detected state, these two states happen concurrently. Siren is on and the system sends notification that an intrusion has been detected so these two things, these two states happen concurrently as part of the intrusion detected state. So we've added a fork and a join here to show that. This gives a stronger sense of concurrency, we've got our initial pseudo state, we have these two sub states of the intrusion detected composite state and the fork here shows us that these are indeed happening at the same time. Siren on after ten minutes and if the alarm is still on the system turns off the alarm, go to the siren off state, when both the siren off state and the sending notification have happened then the system can reset. It can't reset if notification has been sent and the siren is still on, we have to have the siren off state before the reset and then the system goes to the monitoring state which in this simple diagram would be the final state. So you see how our fork and join pseudo state adds some extra information, first that these are happening at the same time and then that they both must reach this pseudo state before the system can reset and we move on to the next state. So again pseudo states are not actual states of the machine but what they do in a sense is fragment the transitions between the actual states.
Tutorial Information
| Course: | UML |
| Author: | Nancy Conner |
| SKU: | 33815 |
| ISBN: | 1-934743-23-2 |
| Release Date: | 2007-10-26 |
| Duration: | 7 hrs / 95 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
VTC Sign up & Benefits
- Unlimited Access
- 81,350 Video Tutorials (14,200 free)
- Video Available as Flash or QuickTime
- Over 715 Courses
- $30 for One Month Access
- Multi-User Discounts Available
