Static algorithms fix a block of storage and retrieval requests,sequence the requests in the block,and execute the resulting schedule ignoring new storage and retrieval requests.Dynamic algorithms re-sequence the storages and retrievals whenever new requests arrive.The static sequencing problem for randomized and class-based storage is believed to be NP-hard,and most algorithms for this problem use a nearest-neighbor heuristic or one of its variations.Han et al.(1987)proposed a match of a storagelocation with a retrieval location that has the minimum travel distance between them. . Lee and Schaefer (1996) developed an assignment formulation and can find an optimum or near- optimum solution for problems of moderate size. The static case for dedicated storage policies can be solved in polynomial time by formulating it as a transportation or assignment problem (van den Berg and Gademann, 1999; Lee and Schaefer, 1997). Table 8 summarizes the static algorithms for differ- ent systems and storage policies. Dynamic algo- rithms in the literature are mainly direct extensions of the static algorithms that re-sequence the requests whenever a new request arrives in the system as reported by Lee and Schaefer (1997), Eben-Chaime (1992), and Ascheuer et al. (1999). Seidmann (1988) proposes a different dynamic control approach based on artificial intelligence techniques.