The program contains a rough theory of mass spectrometry which is still in its formative stages.

ABSTRACT This paper shows how a question-answering system can be constructed using first-order logic as its language and a resolution-type theorem-prover as its deductive mechanism. A working computer-program, Q A3, based on these ideas is described. The performance of the program compares favorably with several other general question-answering systems. The type of questionanswering system considered in this paper is ideally one having the following features: 1. A language general enough to describe any reasonable questionanswering subjects and express desired questions and answers. This paper argues the case for formal methods to achieve such a system and presents one particular approach in detail. The name'question-answering system' requires clarification. The system described above might be named an'advice taker' or a'multi-purpose problem-solving system' or'general problem-solving system'. McCarthy (1958) proposed using formal languages and deduction to construct such a system, and suggested allowing the user to give hints or advice on how to answer a question; he referred to the proposed system as an'advice taker'. Research on'multi-purpose' or'general problem-solving' tends to differ from questionanswering as described above by placing more emphasis on solving deeper, more difficult problems and less emphasis on user interaction, formality, and efficient retrieval of relevant facts from a large data base. The situation is further confused by the use of'question-answering' to refer sometimes to natural language systems, sometimes to information retrieval systems having little deductive ability, and sometimes to systems with deductive ability limited to the propositional calculus. It is important to emphasize the distinction between general versus specialpurpose question-answering. If the class of questions asked of a system is small, completely specified in advance, and concerned with a particular subject area, such as the question-answering system of Green, Wolf, Chomsky, and Laughery (1963) concerned with baseball, or that of Lindsay (1963) concerned with family relations, then we shall call such a system'specialpurpose'. Frequently the goal in designing a special-purpose system is to achieve good performance, measured in terms of running speed and memory utilization. In this case the best approach may be first to construct a special data base or memory that is optimized for that subject area and question class, and then to write special question-answering subroutines that are optimized for the particular data base and question class.

R.M.BURSTALL 373 23 Assertions: programs written without specifying unnecessary order.

R.M.BURSTALL 373 23 Assertions: programs written without specifying unnecessary order.

R.M.BURSTALL 373 23 Assertions: programs written without specifying unnecessary order.

It is a natural generalization of the various versions and extensions of the resolution principle, each of which it includes as special cases; but in addition it supplies all of the inferential machinery which is needed in order to be able to treat the intended interpretation of the equality symbol as'built in', and obviates the need to include special axioms of equality in the formulation of every theorem-proving problem which makes use of that notion. The completeness theory of the generalized resolution principle exploits the very intuitive and natural idea of attempting to construct counterexamples to the theorems for which proofs are wanted, and makes this the central concept. It is shown how a proof of a theorem is generated automatically by the breakdown of a sustained attempt to construct a counterexample for it. The kind of proof one gets depends entirely on the way in which the attempt to construct a counterexample is organized, and the theory places virtually no restrictions on how this shall be done. Consequently there is a very wide freedom in the form which proofs may take: the individual inferences in a proof may be very'small' or very'large' (in a scale of measurement which, roughly speaking, weighs the amount of computing necessary to check that the inference is correct). It is even correct to infer the truth of a true proposition in just one step, but, presumably, to offer such a proof to someone who wishes to be convinced of the proposition's truth would not be helpful epistemologically. His conviction would come, not from contemplating the proof itself, but rather from examining the computation which shows the correctness of its single inference step.

INTRODUCTION Pop-2 (Burstall & Popplestone, 1968) represents a fairly far-reaching revision, extension and systematization of the author's Pop-1 (Popplestone, 1968). The thoughts expressed here consequently represent a point of view elaborated jointly with my co-designer of Pop-2, Dr R. M. Burstall. AIMS POP-2 is a language to be implemented on real machines, using modest resources of manpower. An implementation of the language must be possible which permits large problems to be tackled. This implementation must not be too inefficient in its use of machine time, or too profligate in its use of store. The language must also take into account such properties of real machines as overwritable store--that is to say it must not be a purely constructive language: it must allow assignment. Pop-2 handles a large range of structures such as list cells (cf. CPO and records (called beads in AED).

J. P. Thorne Department of English Language P. Bratley and H. Dewar Department of Computer Science University of Edinburgh 1. INTRODUCTION In this paper we describe a program which will assign deep and surface structure analyses to an infinite number of English sentences.1 The design of this program differs in several respects from that of other automatic parsers presently in existence. All these differences are a consequence of the particular aim we have pursued in writing the program, which represents an attempt to construct a device that will not only assign a syntactic analysis to any English sentence-that is, a record of the syntactic structure that the native speaker Perceives in any English sentence-but which also, to some extent, simulates the way in which he perceives this structure. This is not to say that the analyzer differs from others because we have based its design upon the findings of psycholinguistic experiments. For one thing very few experiments on the perception of syntactic structure have been carried out and for the most part the results have been fairly inconclusive. But it is the case that we have, as far as possible, treated the task of constructing an automatic parser as being itself a psycholinguistic experiment. That is to say, any proposal regarding the possible operation of the program has been judged (mainly as the result of introspection) according to whether or not it seemed to be consistent with human behaviour. And this has led to our incorporating certain features which are absent from other automatic parsing systems. Among the most notable of these features is the program's ability to assign syntactic labels to an infinite number of words while operating with a finite dictionary. As far as we know, all other automatic parsers of English (or 1 This work was supported by the Office for Scientific and Technical Information Grant No. ID/102/2/06 to Professor Angus McIntosh.

SUMMARY This paper describes some of the difficulties in maintaining large computer systems and considers how machine perception techniques can be applied to the problem. A program called the'engineer's assistant' is described as a step in the right direction. Elaborations are made on the meaning of'the right direction', and an experimental implementation of some of these ideas is described. INTRODUCTION A large computer system is usually maintained by a team of engineers. Inevitably these tend to be of different abilities, and some of them become more knowledgeable and therefore more proficient than others in specific areas of the machine. Although computer'down time' has become more expensive by an order of magnitude on present large systems compared to the last generation, the engineers are not mending faults an order of magnitude faster.