Enthuware

Last option is not complete

Can you be more specific of what is missing?

Regarding this option:

Test different clients during the development

If you use simple data types and all your clients respect Basic Profile v1.1 do you need a trial and error test with different clients?

Discuss and define the data types with all the clients in advance and test (from different clients) them thoughout the development phases.

Nothing is said about particular data types so it should be assumed that the types in use are compatible.

If you use simple data types and all your clients respect Basic Profile v1.1 do you need a trial and error test with different clients?

Testing is always good, but when you only use simple data types you would normally find not any issues. Note that compliance to BP v1.1 does not guarantee interoperability.

Nothing is said about particular data types so it should be assumed that the types in use are compatible.

True, BP v1.1 does not say much about datatypes, but they can still cause interoperability issues. The use of xs:integer can for instance cause problems (you should use xs:int instead).