20 - Modifications from previous releases

20.1 - V1.0 to V1.1

The semaphore take now returns a status that indicates if the take attempt timed out or was successfull. The semaphore lifeline gets grayed when the semaphore is unavailable.

20.2 - V1.1 to V1.2

There has been an error in the object orientation chapter: it is not possible to declare a process class or a block class in a block class definition diagram.
Messages now needs to be declared.
Message parameters are now typed with C types.
Parameter length can be omited if the parameter is structured. Then the length is implicitly the sizeof the parameter type.
The VIA concept has been introduced.
Saved messages representation introduced.

20.3 - V1.2 to V2.0

UML class diagram has been introduced
UML deployment diagram has been introduced
Object creation symbol introduced in the behavior diagram
STACK parameter has been added as a parameter when creating a task.
Chapters have been re-organized.

20.4 - V2.0 to V2.1

Messages can have multiple parameters. Declaration, inputs, and outputs have changed.

20.5 - V2.1 to V2.2

Super class transition symbol added
Super class next state symbol added
"Composite state" has been introduced.

20.6 - V2.2 to V2.3

Inline expressions support added.
Property Sequence Charts (PSC) support added.
Change in MSC diagram DTD for textual representation.

20.7 - V2.3 to V2.4

Broadcast introduced.
New representation for behavioral diagrams.