Variables
Variables are measurements or calculations attached to a given production line that produce values either by time or event. Variables can be defined as a discrete date element that provides a location for data storage or generation. Variables are usually lab tests, process values, and so on, for a specific production unit.
The data that populates a variable can be obtained from various data sources. These data sources may need to be interfaced to the system. There are many data types that can be applied to the variable, such as float, string, integer, and so on. You can also apply custom data types. If the data from a variable is being captured in time, rather than by event, then there are many different sampling types (pre-defined simple calculations) that can be applied to the variable.
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Historical variable values are stored in the database.
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Variable data, whether captured manually or automatically, is associated with a production unit event.
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Security applied to a variable overrides security applied to anything above the variable, such as the production unit or line.
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Variables can be moved from one variable group to another
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Variables can be copied between production lines, but they can not be moved.
The Calculation icon 
identifies variables that have calculations attached to them
The Historian icon 
identifies variables that received data from an Historian.
The Manual icon 
identifies variables that receive data that is manually entered through an Autolog display, for example.
The Generic icon 
identifies all other variables.