AaSTIO~Cr It IS possible to significantly reduce the average cost of information retrieval from a large shared database by partltlomng data ~tems stored within each record into a primary and a secondary record segment An analytic model, based upon knowledge of data item lengths, transportation costs, and retrieval patterns, is developed to assist an analyst with this assignment problem The model is generally applicable to environments m which a database resides m secondary storage, and is useful for both unlprogrammlng and multlprogrammlng systems. A computatlonally tractable record design algorithm has been implemented as a Fortran program and applied to numerous problems Reahstlc examples are presented which demonstrate a potential for reducing total system cost by more than 65 percent KEY WORDS AND PHRASES data management, record design, record segmentation, optimization, network flows, btcntenon mathematical programs, branch and bound CR CATEGORIES 3 50, 3 71, 3 72, 5 40, 5 41, 8 1, 8 3

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This paper is concerned with characterizing decision rules for the sequential E-model of chance-constrained programming. A key feature of our characterization will be a detailed discussion of various interpretations of the probability operator in the chance constraints. Specifically we define two new classes of decision rules by exhibiting those sets of constraints which locally support the corresponding probability requirements. The question of how the probabilistic constraints for future periods are affected by previous decisions and realizations of the random variables is considered in detail. Since we are primarily concerned with the feasibility of decision rules, we deal mainly with the constraints of the model. The procedure for selecting the optimum rule from among a particular class of feasible rules depends on the objective function and is briefly discussed in the final section along with some implications concerning the form of the optimum rule. The application of our proposed rules to a two-period example previously appearing in the literature concludes the paper.

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