Creative Design is an activity that involves complex cognitive tasks like analogy and concept composition. This makes the memory structure an important aspect of a Case-Based Reasoning Creative Design System. The indexing structure must support case retrieval based on abstract features and partial case retrieval. This allows the system to perform two important case adaptations: analogy and case composition. In this paper we present an index structure suitable for case retrieval for three adaptation strategies: mutation, composition and thematic abstraction. This memory structure also aids the designer to define and elaborate the design problem. We present the experimental results obtained with CREATOR a case-based design system that uses the memory structure presented in this paper.