InfoPath Dev

It seems to me that I`m understand: DataSources (main and additional) based on data connections , but tell me please, how can I make my data source (from web-service) main?

I don't understand, because I have only one connection to the Web-Service which gets a dataset with one main table and few related tables with repeated data. Related tables - this is a repeated fields (tables) on the InfoPath form. What does main connection mean?

Hi, all. First, sorry for my bad english. I have a web-service. InfoPath gets dataset with EntetyStructure from web-service. In entity presents a fields, which are repeated values. When I drag dataset into the form, creates a ''Repeat table'' control, but option ''Allow users to add or remove rows'' is disabled. How to enable this option?