14456192
Improved interpretation of UNIX-like file names embedded in data
When the data processed by a program span several files, the common practice of including file names as data in some of the files leads to difficulties in moving or sharing that data. In systems using tree structured directories, this problem can be solved by making a syntactic distinction between absolute and relative file names.
14144660
Systematic protection mechanism design
This work describes an attempt to systematically design a hardware resource protection mechanism when given the requirements of a particular language as a target. The design process is formalized as a structured walk through the multidimensional computer design space towards a hypothetical class of optimal machines. Each step in this walk involves a change in the distribution of work between the compiler and run-time system but no change in the source language semantics. The starting point for this walk is the result of a semantic analysis of the language to be implemented; typically, this produces a very high level machine where the compiler, if any, is trivial. The walk ends when no changes result in a net improvement. This does not guarantee that the result is even locally optimal, since the changes tried depend on the ingenuity and persistence of the designer.
 This design approach has been used to arrive at a practical, general purpose protection mechanism oriented towards the needs of the Ada language (preliminary version). This architecture was evaluated by comparing it with the PDP-11/45. For the purpose of this comparison, the protection mechanism was incorporated into a partially specified PDP-11 like instruction set. The number of bits making up the processor state and the number of operations involved in address computation were evaluated. On this basis, the result appears to be competitive and worth further investigation.
14105636
Experience with concurrent simulation
We have successfully implemented a concurrent simulator and we report initial speedup measurements for this technique. Our algorithm requires a shared-memory multiprocessor and is appropriate to any discrete-event simulation model. In addition, our algorithm places no constraints on minimum service times or the presence of cycles in the simulation model. Our experimental simulator runs on an Encore Multimax computer and is applicable to closed product-form queueing networks. We have observed speedups of 2.3 for a central-server queueing model using our simulator.
43650389
An empirical comparison of priority-queue and event-set implementations
Execution times for a variety of priority-queue implementations are compared under the hold model, showing many to be faster than implicit heaps.
42995338
Assembly Language as Object Code
The set of meanings that may be encoded in most object languages is a subset of the meanings that may be encoded in most assembly languages. Careful exploitation of this fact in the design of the SMAL assembly and object language allows the SMAL assembler itself to be used as a linkage editor, thus eliminating the need for an expensive and often misunderstood system program. The SMAL assembler is no more complex than many assemblers in common use today, nor are the relevant aspects of the SMAL language particularly unique.
12941967
Application of splay trees to data compression
The splay-prefix algorithm is one of the simplest and fastest adaptive data compression algorithms based on the use of a prefix code. The data structures used in the splay-prefix algorithm can also be applied to arithmetic data compression. Applications of these algorithms to encryption and image processing are suggested.
11334584
The rapid generation of mutation data matrices from protein sequences
An efficient means for generating mutation data matrices from large numbers of protein sequences is presented here. By means of an approximate peptide-based sequence comparison algorithm, the set sequences are clustered at the 85% identity level. The closest relating pairs of sequences are aligned, and observed amino acid exchanges tallied in a matrix. The raw mutation frequency matrix is processed in a similar way to that described by Dayhoff et al. (1978), and so the resulting matrices may be easily used in current sequence analysis applications, in place of the standard mutation data matrices, which have not been updated for 13 years. The method is fast enough to process the entire SWISS-PROT databank in 20 h on a Sun SPARCstation 1, and is fast enough to generate a matrix from a specific family or class of proteins in minutes. Differences observed between our 250 PAM mutation data matrix and the matrix calculated by Dayhoff et al. are briefly discussed.
6177362
Line and boundary detection in speckle images
This paper considers the problem of detecting lines in speckle imagery, such as that produced by synthetic aperture radar (SAR) or ultrasound techniques. Using the physical principles that account for the speckle phenomenon, we derive the optimal detector for lines in fully developed speckle, and we compare the optimal detector to several suboptimal detection rules that are more computationally efficient. We show that when the noise is uncorrelated, a very simple suboptimal detection rule is nearly optimal, and that even in colored speckle, a related class of detectors can approach optimal performance. Finally, we also discuss the application of this technique to medical ultrasonic images, where the detection of tissue boundaries is considered as a problem of line detection.
12160909
An Architecture For A Universal Lexicon: A Case Study on Shared Syntactic Information in Japanese, Hindi, Bengali, Greek, and English
Naoyuki Nomura, Douglas A. Jones, Robert C. Berwick Massachusetts Institute of Technology, NE43-802 Artificial Intelligence Laboratory nomura@ai.mit.edu Introduction. Given the prominence of the lexicon in most current linguistic theories (LFG, HPSG, GB), the inventory of language particular information left in the lexicon deserves special attention. Constructing large computerized lexicons remains a difficult problem, building a large array of apparently arbitrary information. This paper shows that this arbitrariness can be constrained more than might have been previously thought. In particular, arbitrariness of argument structure, word sense, and paraphrasability will be shown not only to be constrained, but also to be integrally related. Our (radical) view is that variation of lexical behavior across languages is exactly like lexical variation within languages, specifically, the difference lies in the presence or absence of certain morphemes. For example, the fact that Japanese has richer possibilities in certain verbal patterns is derived solely from its morphological inventory.1 Put another way, language parameters simply are the presence or absence of lexical material in the morphological component. Observed language variation patterns reflect morphological systematicity. The generative machinery for producing argument structure positions is fixed across languages. Linguistic Motivation. A striking example underscoring universality of argument structure is the familiar Spray/Load alternation2, shown in (1). Despite the many surface differences in these data across languages, they share several essential properties. (1) a. b. John loaded the hay on the wagon. John loaded the wagon with the hay. Japanese (2) a. taroo-wa teepu-o boo-ni maita. Taro-NOM tape-ACC stick-DAT wrap-PRF 'Taro wrapped the tape around the stick.'
38666741
On Matchings in Graphs
11953858
Joint source channel matching for a wireless image transmission
Application of joint source-channel matching in heterogeneous multi-media environments will demand general source-channel optimization schemes suitable for a wide variety of source coding standards, channel coders, and variable channel conditions. We develop a general approach for joint source-channel matching based on a parametric distortion model that can be accurately applied to most classes of source and channel coders. Our simulations indicate that it may be possible to obtain nearly all of the benefits of joint source-channel optimization by matching existing source and channel coding standards using the simple and general approach we propose.