We have to present the development plan for a new feature in a software product. To properly capture the use cases I want to implement a prototype first and then analyze this prototype together with the customer. The problem is the customer often asks "if it's a prototype, does it mean you'll throw it away when the analysis phase is done?"; my team does not work this way: although we call it a prototype, the team members always write production-quality code and when the analysis phase is done at least 80% of the "prototype code" will be used in the production code. So I try to use the term "skeleton", but I'm not sure it's the optimal one. Can you suggest a better term?
You can call it a skeleton, a skeletal program or you can use the term 'bare bones'. I don't think there's a great deal of difference between them.
The terms "Alpha version", and "Beta version" are well known.
An alpha version is known not to fully meet the specifications, and is subject to testing in-house.
A beta version is a feature complete, but possibly still buggy piece of software, that may be shown to customers for evaluation and feedback.
If you want to imply that you think the software is incomplete call it an alpha version. If you want to suggest it is already usable call it a beta.