I have been using HAP for more than 7 years, and have faith in it.
Waht i suggest you is that rather than reading a practical example, i send you a HAP project archived file (.E3A) which you can retreive into Your HAP program and there you can see all the spaces, systems and plants that are designed. You can explore the inputs / outputs of different kinds. If you want, i can send you projects of more kinds w.r.t. applications. and if you have some questions for clarification, dont hesitate to come back to me.
Just tell me which version of HAP you are using.