If you have been interacting with the client for gathering the REQ need to explain them on what basis the req were gathered.

These are the things you can ask the client to get the requirements:

1. What is the problem? This will give answer for why they are going for XI? Here try to Understand the business as well as integration? Where XI come into the picture?
2. Total number of systems involved in integration? That is their SLD? Details?
3. Scenarios (interfaces)? Total? What kind of? But here once again this is depends on project. Some TIMES client will give this (or) based on the requirement you people have to decide? It is fully depends..!!!! take care
4. Then based on the scenario you need to get the full information ....this is place where you can ask all the QUESTIONS from scenario to scenario. Get all the details as mentioned below apart from the basics try to ask something technically.
5. Are they providing any XSD,WSDL, documents, Naming conventions..etc
6. Protocols related like http, ftp, smtp, soap....
7. If file related then CSV, Fixed....like that delimiter specific details.very IMP this one.
8. If R/3 present then ....it is Idoc, Rfc, BAPI,....any proxies and web SERVICES for direct communication ....etc

These are the basic things for XI integration project and after that every thing is specific to scenarios.

If you have been interacting with the client for gathering the req need to explain them on what basis the req were gathered.

These are the things you can ask the client to get the requirements:

These are the basic things for XI integration project and after that every thing is specific to scenarios.