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The scientific correspondence between Harrod and Robertson was initiated by Harrod’s criticism of Robertson’s Banking Policy and the Price Level (1926).⁷ Harrod first wrote on 18 May 1926 (letter 2) raising at once the following “salient point”: Much of your argument depends on the view that justifiable expansions and contractions as defined by you are desirable. Why are they desirable? You give reasons on p. 22 why you think some instability in output desirable. But the reasons mentioned there (and I can’t find any others) don’t seem particularly directed to show that the special form of instability constituted by the so-called “justifiable” expansions and contractions is desirable. They seem to me to show that perhaps some instability, that, presumably, of less degree than we have been accustomed to in the past, is good, but by no means precisely how much is good. Thus, suppose the “hypothetical group member” or “the actual workman” of p. 19 were able to govern output according to their own self interest, there would still, according to the arguments of ch. 2, be some instability. Would not that be enough? Or if you want more, why stop at the “justifiable”? Why not have some of that due to “secondary” causes? It seems to me that you have been led away by purely aesthetic interests to identify that more moderate amount of instability which we really need (as shown on p. 22.) with that which we would get: (i) if secondary causes were removed; and (ii) if control of output stayed where it is now – in the hands of the entrepreneur. I don’t see how you can say to the banks more than “damp down fluctuation a bit, but leave some fluctuation, as that is healthful for the body economic”.He added two notes to his letter, in the first of which he commented upon the four proposed courses of policy outlined by Robertson on pp. 25–26 of his book. In the second note Harrod suggested that Robertson’s calculations in Appendix I to Ch. 5 of Banking Policy assumed the following behaviour of the public: (i) People do not allow for the effect of their withholding on the price level (this is reasonable). (ii) They are ignorant as the future course of inflation (or do nothing to meet it). (iii) On this basis they decide what withholding is necessary to restore H, decide that it would be too much effort to restore it at once, and…spread the restoration over K – 1 days. It so happens that by choosing K – 1 their 2 errors (or failures to take everything into account) cancel each other out, and they do effect the restoration in that time. If K or K – 2 had been chosen, this would not have been so.Harrod further argued that Robertson’s “so-called reasonable assumption of a restoration in K – 1 days is purely arbitrary,” and that “all this reasoning is rendered of doubtful value by the fact that we must suppose an alteration in view as to ‘the appropriate proportion between Real Hoarding and Real Income’ during the process of inflation. Not only will people not replenish H at once, but they may well voluntarily reduce it.”

This paper is concerned with recent work in the theory of information retrieval. More particularly, it is concerned with theories which tackle the problem of retrieval performance, in a sense which will be explained. The aim is not an exhaustive survey of such work; rather it is an analysis and synthesis of those contributions which I feel to be important or find interesting.

This chapter attempts to untangle the complex arena of private sector engagement in education by discussing the definitional challenges associated with understanding the non-state sector and by introducing some conceptual frameworks employed in research on private education. A thematic review of research from the field of Comparative International Education is provided to give the reader an understanding of the diversity that characterizes private involvement as well as the interconnectedness of private actors, specifically drawing attention to findings that grapple with equity implications. The chapter concludes with some suggestions for developing a framework for research via posing questions that ought to be asked when designing, conducting and analyzing findings from studies into private sector engagement in education.

Information science, or informatics, has almost from its beginnings been characterized by a seemingly inordinate self‐consciousness, exemplified by concern with its status vis‐à‐vis other disciplines, with its status as a science, and with the significance of its objects of investigation and the goals of that investigation. The bibliography by Port, and the survey by Wellisch, of definitions of information science, and the historical survey by Harmon, all give substantial evidence of this self‐consciousness. Some aspects of this attitude are of course due to the social and political problems facing any new discipline (or field of investigation aspiring to such status), such as indifference or hostility from the established academic community, the fight for a share of limited research and development funds, the inferiority complex associated with having no well‐defined methods of investigation in a social situation which requires them for acceptance, and so on. Other aspects of this self‐consciousness may, however, be more related to strictly internal, ‘scientific’ concerns; that is, to problems within the theoretical structure of information science which must be solved in order for substantial progress in solving its practical problems to be made. This review surveys contributions to one such problem: the question of a suitable concept of information for information science.

In beginning its work at the end of the 1950s, the Aslib Research and Development Department inevitably faced the task of identifying the most significant problems for investigation, at the same time having the need to establish appropriate experimental techniques. Most of the projects undertaken since that time have dealt with current problems, and to an extent the advent of new technologies and techniques to the information world (mechanization in the 'sixties, management studies in the early 'seventies, on‐line working and publication problems in more recent years) is reflected in the work reported below. What follows is a complete bibliography of publications by members of the Department from its formation up to the end of 1977.

The progress of parallel computing in Information Retrieval (IR) is reviewed. In particular we stress the importance of the motivation in using parallel computing for text retrieval. We analyse parallel IR systems using a classification defined by Rasmussen and describe some parallel IR systems. We give a description of the retrieval models used in parallel information processing. We describe areas of research which we believe are needed.

In the 1960s those on the political left flattered themselves that the vast number of publications by socialists, anarchists, feminists, and other groups on that wing of the political spectrum were evidence of the rich intellectual life of the struggle to create a progressive America. Conversely, the lack of publishing by the right was evidence of a general lack of intelligence. But that was then, and this is most certainly now. The right in America has moved from margin to center over the last two decades, vindicating former Attorney General John Mitchell's boast that “the country is going so far to the right that you won't recognize it.”

The term selection problem for selecting query terms in information filtering and routing has been investigated using hill‐climbers of various kinds, largely through the Okapi experiments in the TREC series of conferences. Although these are simple deterministic approaches, which examine the effect of changing the weight of one term at a time, they have been shown to improve the retrieval effectiveness of filtering queries in these TREC experiments. Hill‐climbers are, however, likely to get trapped in local optima, and the use of more sophisticated local search techniques for this problem that attempt to break out of these optima are worth investigating. To this end, this paper aims to apply a genetic algorithm (GA) to the same problem.

A standard TREC test collection is used from the TREC‐8 filtering track, recording mean average precision and recall measures to allow comparison between the hill‐climber and GAs. It also varies elements of the GA, such as probability of a word being included, probability of mutation and population size in order to measure the effect of these variables. Different strategies such as elitist and non‐elitist methods are used, as well as roulette wheel and rank selection GAs.

The results of tests suggest that both techniques are, on average, better than the baseline, but, the implemented GA does not match the overall performance of a hill‐climber. The Rank selection algorithm does better on average than the Roulette Wheel algorithm. There is no evidence in this study that varying word inclusion probability, mutation probability or Elitist method make much difference to the overall results. Small population sizes do not appear to be as effective as larger population sizes.

The evidence provided here would suggest that being stuck in a local optima for the term selection optimization problem does not appear to be detrimental to the overall success of the hill‐climber. The evidence from term rank order would appear to provide extra useful evidence, which hill climbers can use efficiently, and effectively, to narrow the search space.

The paper represents the first attempt to compare hill‐climbers with GAs on a problem of this type.