Purpose
CO Validations to additional authorisations checks.
Overview
Standard Authorization Objects and Organizational Units allow you to control business transactions.
Requirement and Solution:
Now of you would like to control the authorization to post a document on a WBS element verifying the field location available on the WBS element, how do we achieve that?
If a certain GL account postings are allowed against a specific set of WBS elements, how can we do that?One Simple and easy (also standard) solution is to use CO line item validation.
Why CO Line item Validation?
In actual posting if the receiver object is a WBS element (which is a CO object) system would create a CO document with line items.
Example CO Validation to meet Requirement 1:
To check if the user is allowed to post actual against a WBS element provided he/she is authorized for the location field available on the WBS element.
T Code OKC7
Prerequisite: If WBS element is not blank AND field location on the WBS is within the set (ranges of location)
Check*: The valid user to use the WBS is 'KADIAMS'
Error if prerequisite is met and check is not fulfilled.
Creation of Sets for Location:
T Code GS02
*- Instead of specific user, user groups or sets of user ID can also be used.
WBS Master Data
Posting a document against WBS activating the above CO line item validation results in error for user ID 'JAINA' as the WBS has location field falls within the location set. 
Posting a document against WBS activating the above CO line item validation does NOT result in error for user ID 'KADIAMS' as the WBS has location field falls within the location set. 
Available Structures from where the Perquisites/Check fields can be used.
Example CO Validation to meet Requirement 2:
To check postings on the specific GL account (cost element) is possible on to specific WBS element whose 1st character is M. 
Posting a document against WBS activating the above CO line item validation results in error when GL account 441110 is used against WBS number which starts with M. 
Other Information:
- Options for checks and prerequisites are numerous with the available functions for validations.
- Using sets would involve data maintenance if any additions or deletions needs to be done.