SRM doubts

Gurus,

I am in the process of understanding the SAP SRM system as we plan to implement it soon and have a sandbox system in place. We have no MM implemented at the moment. We plan to start off with indirect procurement. We plan to have a few catalogs that use online and our employees would be able to order from them. I have a few questions regarding self-service procurement scenario.

1. Can the Purchase orders be created in the backend without a material master available?

2. How important is the IPC (the relevance of IPC)?

3. Is it possible to suppress some of the fields on the shopping cart ordering screen?

Thanks in advance!

Regards

Robert G