Each Key Code in an hri07e project is intended to add value to the dsign process as well as enable future automation via XML data access. It is important that as each design activity progresses - that the designer identify the critical data elements that have been created by the process and if possible use existing ones. If they have a reason to not use an existing key code intended for the same purpose then they should define a new key code - and why it is diffreent from any other key codes that have previously been generated for the same purpose.
Also - while it is important to generate suffcient key codes to define the deign, overlapping and redundant key codes can cause the project much grief when the physical object gets created from two differing values for the same dimension or material or whatever. Typically - the first one wins and everything that used the second one doesn't fit or work. This is a bad thing - to misquote Martha Stewart.