In eXpress, functions are used to represent the specific mechanism(s) of an objectthat causes it to perform in a particular manner. For example, in a hydraulic design, a simple two-state valve may have two functions, one when the valve is in the open position and another when the valve is closed. As functions are defined on individual objects, eXpress automaticallypropagates the functionsto establish signal flow through the model.
Functions can be classified into one of three types:
NOTE: Output Dependencies can only be setup on the model level. For setting output dependencies on a Hierarchical Object Port you must descend to that model level and set the dependency on the port driving the output flag. Where multiple functions are defined the IO Flag should be set to multiple. See
- Dependencies on the Ports of an Object define how that input port or output port performs.
The Default for"Output port functions" dependencies is all inputs. These dependencies can be propogated throught the Object either Passive or Active.
It is up to the analyst to modify these dependencies to describe the real world perfomance of that Object.
Function dependencies on input ports are derived from the functions on the net to which the port is connected.
See Function How To's for setting up both input and output Function dependencies
When to Use Functions
Functions should be used to provide the appropriate level of resolution needed by the diagnostics. Before a model is started, it is vital to identify the level of detail to which functions should be modeled. There are dangers in creating both too many or too few functions. Creating too many functions can lead to a dramatic increase in the number of hours spent modeling and can significantly impact the amount of time needed to make changes to the model. Creating too few functions may prevent tests from being defined with the resolution necessary for diagnostics to accurately and effectively assess the design.
