I have a codebase, which will be used by several applications.
What techniques would facilitate this requirement (service layer?)?
Thanks
I don't see what your actual question is, but I can tell you that a Service Layer is unlikely to be what you're after.
A service layer will provide communication between systems (including ones that are built on different platforms); and a messaging based approach can also be used between components or layers within a system (application). Sharing all or part of a code-base is not a requirement in either of these scenarios.
I have a codebase, which will be used by several applications.
You have a codebase or you're going to have? "Will" infers you're not there yet.
What techniques would facilitate this requirement?
What requirement exactly? If you meant "going to have" then I guess you're after guidelines on writing code that can be re-used by several applications?
Give us some more info and I'll expand my answer :)