I think this is something realy cutomer specific.
It depends what kind of information you want to query for in regard of information reuse.
e.g. you store a specific number from your plm system visible into a udf to be able to find this specific line item for reuse or modify. ... or you want to create reports based on some informations in your line items ... in that case you can store them also into the udf's and reuse them for some queries. ... Or an ordernumber which comes from a diffrent system but has to be published to better find this lineitem to work on it. (if more departments work with the same line item)