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Research and Advances Jul 1 1987

Adjacency detection using quadcodes

A method is presented for determining whether two given regions are adjacent, and for finding all the neighbors of different sizes for a given region. Regions are defined as elementary squares of any size. In a companion paper [2], we introduce the quadcode and discuss its use in representing geometric concepts in the coded image, such as location, distance, and adjacency. In this paper we give a further discussion of adjacency in terms of quadcodes. Gargantini [1] discussed adjacency detection using linear quadtrees. Her discussion was applied to pixels, and a procedure was given to find a pixel's southern neighbor only. This paper considers elementary squares of any size, and gives procedures for both aspects of the problem: for determining whether two given regions are adjacent, and for finding all the neighbors of different sizes for a given region.
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Research and Advances Jul 1 1987

The quadcode and its arithmetic

The quadcode is a hierarchical data structure for describing digital images. It has the following properties: (1) straightforward representation of dimension, size, and the relationship between an image and its subsets; (2) explicit description of geometric properties, such as location, distance, and adjacency; and (3) ease of conversion from and to raster representation. The quadcode has applications to computer graphics and image processing because of its ability to focus on selected subsets of the data and to allow utilization of multiple resolutions in different parts of the image. A related approach is the quadtree. Samet recently presented a thorough survey of the literature in that field [7]. Gargantini [2] and Abel and Smith [1] presented linear quadtrees and linear locational keys that are efficient labeling techniques for quadtrees. In those papers the geometric concepts of the image are discussed by using the tree as an interpretive medium, and the approaches and procedures are based on traversal of the nodes in the tree. In this paper we present the quadcode system, which is a direct description of the image, and discuss the geometric concepts in terms of the coded images themselves.
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Research and Advances Jul 1 1987

Word division in Spanish

Spanish is a language with very precise and regular orthographic rules. A syllabication algorithm strictly based on syntactic analysis, not requiring any semantic knowledge, is presented and further extended to include hyphenation. Algorithms are presented as pattern matching schemata, and efficient implementations are considered.
Research and Advances Jun 1 1987

Rule-based versus structure-based models for explaining and generating expert behavior

Flexible representations are required in order to understand and generate expert behavior. Although production rules with quantifiers can encode experiential knowledge, they often have assumptions implicit in them, making them brittle in problem scenarios where these assumptions do not hold. Qualitative models achieve flexibility by representing the domain entities and their interrelationships explicitly. However, in problem domains where assumptions underlying such models change periodically, it is necessary to be able to synthesize and maintain qualitative models in response to the changing assumptions. In this paper we argue for a representation that contains partial model components that are synthesized into qualitative models containing entities and relationships relevant to the domain. The model components can be replaced and rearranged in response to changes in the task environment. We have found this "model constructor" to be useful in synthesizing models that explain and generate expert behavior, and have explored its ability to support decision making in the problem domain of business resource planning, where reasoning is based on models that evolve in response to changing external conditions or internal policies.
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Research and Advances Jun 1 1987

Relationships between selected organizational factors and systems development

Three organizational variables influence the quality of the system development process: available resources (both human and financial), external influences on the development process, and the project team's exposure to information systems. Public information and interviews with systems managers from 28 large private firms yielded data about the organizational variables. Systems project group members completed questionnaires concerning the system development process. The results indicate that human resources affect the development process positively, but increased financial resources are related to team disagreement. The degree of external influence on the system development effort needs to be carefully monitored and controlled. Systems exposure in the firm allows an increase in the degree of awareness among project group members about the different problems encountered by users and systems staff.
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Research and Advances May 1 1987

A statistical technique for comparing heuristics: an example from capacity assignment strategies in computer network design

An analysis of variance (ANOVA) model is developed for determining the existence of significant differences among strategies employing heuristics. Use of the model is illustrated in an application involving capacity assignment for networks utilizing the dynamic hierarchy architecture, in which the apex node is reassigned in response to changing environments. The importance of the model lies in the structure provided to the evaluation of heuristics, a major need in the assessment of benefits of artificial-intelligence applications. A nested three-factor design with fixed and random effects provides a numerical example of the model.
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Research and Advances May 1 1987

An empirical validation of software cost estimation models

Practitioners have expressed concern over their inability to accurately estimate costs associated with software development. This concern has become even more pressing as costs associated with development continue to increase. As a result, considerable research attention is now directed at gaining a better understanding of the software-development process as well as constructing and evaluating software cost estimating tools. This paper evaluates four of the most popular algorithmic models used to estimate software costs (SLIM, COCOMO, Function Points, and ESTIMACS). Data on 15 large completed business data-processing projects were collected and used to test the accuracy of the models' ex post effort estimation. One important result was that Albrecht's Function Points effort estimation model was validated by the independent data provided in this study [3]. The models not developed in business data-processing environments showed significant need for calibration. As models of the software-development process, all of the models tested failed to sufficiently reflect the underlying factors affecting productivity. Further research will be required to develop understanding in this area.
Research and Advances May 1 1987

Computer Science Program Accreditation: the first-year activities of the computing sciences accreditation board

This report summarizes the activities of the Computing Sciences Accreditation Board from its inception in 1984 through its first accreditation cycle completed in June 1986. The major activities during this period were directed at developing the CSAB structure necessary to carry out the accreditation process, and at conducting the first round of accreditation visits and actions.
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