Thomas N. Hibbard

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much more efficient internal sort than either of the four techniques previously published. The additional space required is one word per record. Therefore, given a memory area of size A and a record of size S, then the number of records (N) that can be sequenced in memory using the Replacement Selection technique is A/(S+i), as compared to A/S for other(More)
A preliminary example of program development demonstrates that the control-independent implementation of data types can lead to very inefficient code. The concept of a data space, which emphasizes the interaction between data and control structures, is introduced as a formal model of virtual machines. The model consists of three components: a state space X,(More)
A phrase structure grammar is called <italic>context-limited</italic> if there exists a partial ordering on its alphabet such that any letter on the left of any production is less than some letter on the right of the same production. It is proved that context-limited grammars are equivalent to context-free grammars, the equivalence including ambiguity. The(More)
In the mathematical framework of data spaces the paper develops some important general principles of information structuring. These principles are related to the notions of redundancy of information, completeness of a set of access paths, information sharing and compounding, and virtual access to information. The results are relevant to both sequential and(More)