There are several strategies fo Value mapping
1) Fixed values (e.g. constants in Graphical mapping)
2) Value mapping on Jave stack via VM tables
3) SAP tables created in SE11 and RFC the data from calls from the Java stack
Surely the best strategy is 3) even though it is not the most efficient purely for the fact to have easy visibility of your integration data. e.g. via SM30 or custom transaction to view integration value mappings. If anyone has a different view on this I would to hear from them or possibly suggest an alternative.