Master variables are variables that can be defined once and applied to each process definition that is created.  For example, if customerID is used on every definition, instead of defining the variable for each definition, customerID can be defined using the master variable screen. Once the variable is defined using the master variables, each new definition will automatically have the “customerID” variable. 

Master variable UI for defining variables look as follows:

Add variables by entering the name of the variable and by selecting a data type for the variable. Remove any variables by selecting them from the list. The 'Variables / Globals have default values based on type' functionality in the Process Instances page.

• Variables and globals have '0' for the 'Number' data type
• Variables and globals have ' ' for the 'String' data type
• Variables and globals have 'Current date and time' for the 'Date' data type
• Variables and globals have 'false' for the 'Boolean' data type