ENVIRONMENT
|
|
SEA ENVIRONMENT |
|
FEATURES |
OVERVIEW |
|
|
A homogeneous model for heterogeneous systems (continuous, discrete,
various application domains) based on Predicate/Transition-Nets (Pr/T-Net)
has been developed. Systems and their states are represented in an application
oriented way abstracting from the underlying Pr/T-Net.
Pr/T-Nets unambiguously define the semantics of the
graphical system specification and are used as a basis for
simulating/animating the system specification. SEA allows to easily
incorporate arbitrary user defined or standardized graphical symbols
and their behaviour. Via this approach a unified semantic basis
for different graphical specification formalisms/techniques can be
provided. These techniques may be application independent like data
flow graphs, state charts or block diagrams for differential
equations or application dependent like logical gates for hardware systems.
Due to the underlying common semantics defined by extended Pr/T-Nets,
a heterogeneous system can be specified and simulated
as a whole at very early stages of design before some system components
(e. g. the mechanics) are already constructed.
Also, the crucial points of these systems,
i. e. the interfaces between system parts of different application
domains, can be validated. Development time and costs are reduced considerably,
since errors are detected in an early stage of development. |
|
THE
ENVIRONMENT |
|
| Actually the design environment consists of a browser for the selection of existing or new nets or subnets, a Pr/T-Net-Editor for a comfortable editing and simulation of Pr/T- Nets, and a Pr/T-Net-Interface-Editor for the definition of abstract graphical representations for subnets. Some important features of the design environment are: |
|
Mixed Editing and Simulation of Extended Pr/T-Nets |
||
| With the Pr/T-Net-Editor it is possible to edit and simulate the net alternately without intermediate compilation steps. During such an edit-simulate-sequence it is even possible to change the actual net marking and continue simulation on this new marking. Markings reached during the simulation can be saved and reused as starting points for further simulation steps together with new markings generated with the editor. This feature allows a very flexible handling of stimuli which is especially valuable during the development phase of a system. |
|
Mixed Top-down and Bottom-up Specification of Hierarchical Pr/T-Nets |
||
|
In the same design some parts may be specified in top-down manner while
other parts are specified in a bottom-up fashion. After completion of the
specification the consistency can be checked explicitly. If the same subnet
is used several times in a specification, only the dynamic net information
is copied and the static information is instantiated. This avoids redundant
storage of the same information. |
|
Abstract Representations of Subnets |
||
| With the Pr/T-Net-Interface-Editor an abstract representation for a subnet can be specified. If the subnet is used in the definition of another net, only this abstract representation is visible. During the simulation of the subnet the firing of a transition may cause a change of the abstract representation. Hence, the abstract representation reflects the state of the subnet. The previous page shows the Pr/T-Net-Editor during the simulation of a Pr/T-Net specifying the control of traffic lights at an intersection. In the net for the intersection the abstract representations of the subnet for the traffic light (instantiated twice) and the subnet for the control of the intersection are shown. On the right hand the Pr/T-Net-Definition for the traffic light is depicted. It shows the actual state of the left traffic light which means the transition ''Green'' has finished its firing cycle (its output place is marked). The abstract representation in the net for the intersection reflects this state. |
|