System Expressions and Constants are a way to add a column of data to a process, that is independent of the source data.
The column can help with audit ability of the processes, for example when you are loading data from multiple sources into a common destination.
Eightwire has a number of expressions that provide metadata about the data transfer, as follows;
Assign a system expression to a process
Within a Process Group, hover over a process to edit it.
Click Edit Process
Click +Add System Column
Assign a field name for the column and select a system column type (for example BatchExecuteDate or BatchID).
Click on the source System Column and then click on a destination column to map them.
Checkout the section on Process Expressions Syntax - to see all the available functions.
A constant is a fixed data value — it is not calculated and cannot change. Use a constant in a column where you want to hard code a value into a process that does not exist in the source data.
For example when transferring the type of data into one destination from multiple sources, it may be useful to include the name of the source as a Constant column for each respective Process.
When the data is written to the destination then the constant will be written to the destination column - as mapped in the process.
Make sure the Data you use in a Constant - can be written by ensuring it is a TEXT in the destination - you cannot cast a Constant unless you use an Expression instead.
More options working with processes are in the following pages;