The WorldModel Component
Parameters:
Description:
The WorldModel component is a very simple, equation-less model that consists of only one parameter:
model worldModel
extends Modelica.Blocks.Interfaces.BlockIcon;
parameter Integer qss=1;
equation
...[annotation]...
end worldModel;
It has to be inserted in every model, and its parameter qss is used to set the parameter $method$ in the model's others components.
But how is it possible to set a parameter by means of a parameter of another component? The solution in this context is the Modelica "inner/outer" language construct (cf. [Modelica]): "If a variable or a component is declared as outer, the actual instance is defined outside of the defining class and is determined by searching the object hierarchy upwards until a corresponding declaration with the inner prefix is found."
Every block contains therefore an outer variable world of the type worldModel and uses the variable world.qss in order to set the parameter method:
model anyBlock
parameter Integer method=world.qss "Use QSS1, QSS2 or QSS3";
outer ModelicaDEVS.Templates.worldModel world;
By definition, the model itself has to contain a component called $world$ of the type worldModel that is declared as "inner". In order to automatically guarantee these settings for all instances of the WorldModel component, the WorldModel features the following annotation properties:
annotation (defaultComponentName="world",
defaultComponentPrefixes="inner",
Diagram,
Icon([Icon definitions])
);
The true value of method in any block that is present in a model that also contains the WorldModel is then determined by the WorldModel.qss parameter. Assume a simple toy model, only consisting of a Ramp block and the compulsory WorldModel component. The figure below shows how the method parameter of the Ramp block is defined by setting the qss parameter of the component world:
The method parameter determines whether to use QSS1, QSS2 or QSS3 specifications. The presence of the WorldModel component allows the user to switch the method parameter of all blocks in a model at once instead of being forced to switch it for each block separately. Then again, it is still possible to assign a fixed value to the method parameter of certain blocks if this is desired: simply open the parameter window of the block in question and modify the parameter $method$ manually. Thereby, method becomes independent of world.qss, and hence, a modification of qss in the WorldModel will not effect it anymore.
Note that blocks that lack a parameter method produce output events that are valid for any type of QSS, and are never influenced by the WorldModel.
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