Well ... again my favorite "glue tool" is the service contract. Yeah, I know we need to improve it. I've been giving thought to writing a higher-level declarative layer, just as I'm now doing for forms. That would remove some of the boring and tedious aspects of working with service contracts (repetitive SQL in Oracle and SQL versions). Janine Sisk and I have also talked about providing default values and named parameters on the calling side. There are other things that could be done to make using service contracts pain free.
If the need is there to provide PL/SQL functions that can be used in queries, you could define a standard parameter signature and just have the contract return the name for that package. Something like that.
Service contracts are nice because they provide us with on mechanism for "gluing" pieces together. I fear ad hoc approaches because everyone has the tendency to do theirs slightly differently ...
