View source for EMK:System Definitions

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[[File:System Definitions.jpg|230px|thumb|right|Example System Definitions Window]]
System Definitions allow you to change multiple Run Definitions simultaneously with little effort. At run time values assigned to System Definitions automatically replace any reference to the System Definitions in the Run Definition.

The '''''System Definitions Window''''' is accessed through the drop down '''''Resources''''' Menu at the top of the '''''[[EMK:Main Window | Main Window]]''''' by clicking on the ''System Definitions'' tab.

'''System Definitions Window Fields'''
{|class="wikitable"
|-
| ''Name'' || Identifies the System Definition. In order to be recognised all System Definition names must begin with the “$” character
|-
| ''Definition'' || Specifies the "value" associated with the system definition
|}

Once a System Definition is created, it can be used in any EMarket field defining a Resource Instance.

For example, if the System Definition named ''$StartDate'' has the value ''1 July 2005'' and a Run Definition has '$StartDate' entered in to the ''Start Date field'', the Run will be executed with a start date of '1 July 2005'.

System Definitions can also be used to replace starting storage values or parts of formulae. For example an Offer Price might be defined as '$DieselCost / 0.4' where the name '$DieselCost' has been given a System Definition. Some numeric fields may not allow System Definition names to be entered.

If the substitution produces an invalid field entry EMarket will produce an error message.  For example, if ‘$StartDate’ was given the definition ‘2005’ in the example above then the run would terminate with the message ‘Invalid start date: 2005’


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