Idea association involves a dynamic linking process among ideas, cases and the links themselves. Based on the knowledge representation issue-concept-form proposed by Oxman (1994), design ideas, cases and links are elucidated. Furthermore, various and dynamic linking plays are involved in two steps: divergent, in which alternative idea entities are linked, and convergent, in which these idea entities are selected. These linking plays provide a computational mechanism for indexing prior design cases dynamically. Finally, an index prototype for supporting the linking process of idea association, called Mapmaker, is proposed in this paper.