ICONIX provides more requirement and design documentation than XP, and aims to avoid analysis paralysis.
Robustness analysis reduces the ambiguity in use case descriptions, by ensuring that they are written in the context of an accompanying domain model.
The ICONIX Process is described in the book Use Case Driven Object Modeling with UML: Theory and Practice[1].
A robustness analysis is performed to find potential errors in the use case text, and the domain model is updated accordingly.
During this stage of the ICONIX process the domain model and use case text from milestone 2 are used to design the system being built.