AS is basic granularity in BGP in the sense that one ASN should not be multiple times in AS PATH, and it is generally assumed that ASs are internally connected

AS is basic granularity in BGP in the sense that one ASN should not be multiple times in AS PATH, and it is generally assumed that ASs are internally connected (although for non-transit networks, this could be workarounded in several ways) But basic routing entity in BGP is still prefix/route, and different routes of one AS can be announced in different ways.