Showing papers on "Object (computer science) published in 1978"

Naming and synchronization in a decentralized computer system

Abstract: In this dissertation a new approach to the synchronization of accesses to shared data objects is developed. Traditional approaches to the synchronization problems of shared data accessed by concurrently running computations have relied on mutual exclusion -- the ability of one computation to stop the execution of other computations that might access or change shared data accessed by that computation. Our approach is quite different. We regard an object that is modifiable as a sequence of immutable versions; each version is the state of the object after an update is made to the object. Synchronization can then be treated as a mechanism for naming versions to be read and for defining where in the sequence of versions the version resulting from some update should be placed. In systems based on mutual exclusion, the timing of accesses selects the versions accessed. In the system developed here, called NAMOS, versions have two component names consisting of the name of an object and a pseudo-time, the name of the system state to which the version belongs. By giving programs control over the pseudo-time in which an access is made, synchronization of access to multiple objects is simplified. NAMOS is intended to be used in an environment where unreliable components, such as communication lines and processors, and autonomous control of resources occasionally cause certain objects to become inaccessible, perhaps in the middle of an atomic transaction. Computations may also suddenly halt (perhaps as the result of a system crash) never to be restarted. NAMOS provides facilities for recovering from such sudden failures, grouping updates into sets called possibilities, such that failure of any update belonging to a possibility prevents all of the other updates in the possibility. The naming mechanism of NAMOS also provides a useful tool for restoring a consistent state of the system after a failure resulting in irrecoverable loss of information or a user mistake resulting in an inconsistent state. An important motivation for the development of NAMOS is the need to support decentralized development of application systems by combining existing application systems that deal with shared data. NAMOS supports the construction of modules that locally ensure their own correct synchronization and recovery from inaccessibility. Larger modules that use several separately designed modules can then be constructed, perhaps with additional synchronization constraints, without modifying the modules used. In most systems based on mutual exclusion, such post hoc integration of modules is difficult or impossible.

Arrangement for sensing the geometric characteristics of an object

Abstract: A plurality of projectors are positioned in spaced relationship about an object with a surface to be geometrically analyzed. The projectors have cooperating masks which project onto the object illuminated patterns that subdivide the object into predetermined sections. Each mask has a predetermined pattern of sections, and is applied in sequence. The masks are cooperatively advanced in the projectors, with a separate illuminating pattern prevailing on the object each time that the masks are advanced. The combinations of the patterns on the masks define closely-spaced sections subdividing the object. The patterns are coded so that each section is uniquely defined in coded form. Cameras having the entire object within their field of view, photograph the object each time a separate mask is applied.

The PADL-1.0/2 system for defining and displaying solid objects

Abstract: PADL (Part and Assembly Description Language) is a language for defining solid objects via constructive solid geometry, i.e. as (regularized) set-theoretical compositions of primitive solid “building blocks”. The current processor for Version 1.0 of the language accepts PADL statements either in batch or in keyboard-interactive mode and produces line drawings of objects on CRT's and plotting devices. A variety of drawing styles is available: dimensioned orthographics, perspectives, section views, interference drawings, etc.Novel characteristics of the PADL-1.0/2 system include 1) general combinational operators that may be applied to any part defined in PADL, 2) correct handling of “pathologies” that occur when (for example) two objects have partially coincident boundaries, 3) maintenance of consistent multiple representations of the same object, and 4) automatic posting on drawings of dimensions to reflect user-defined geometric relations between features of objects.This paper provides an overview of both the language and the current processor's capabilities and organization. Detailed discussions of the underlying mathematics, algorithms, and implementation are presented elsewhere.

Computer-generated display for a fire control combat simulator

Abstract: Electronic generation of the display is accomplished by a system which includes a host computer, a plurality of object generators, and related circuitry. Each object generator contains a memory which stores the image of an object which may be displayed on the video display. The host computer assigns locations in the scene to the objects of each object generator. Each object generator includes its own microprocessor which performs calculations based on its own object information and position and range information received from the host computer to provide appropriate video signals for the display. The related circuitry of the system includes a blanking and count generator which provides signals whereby the color video information from the object generator is displayed on the video display and it also establishes times for permitting updating of the information between the host computer and the object generators. Further features include a priority chain linking the object generators which, if an overlap situation occurs where more than one object generator is calling for its information to be displayed in the same location on the video display, the object which has been assigned a higher priority, indicating that it is at a closer range than others, has its overlap information displayed on the video display instead of those of lower priority. Another feature is the data compression scheme employed to store the object image in each object generator.

Representation of Three-Dimensional Objects.

Abstract: : This paper describes a system for generation and representation of computer models of arbitrary three dimensional objects. Three representations are explored which have varying time and space tradeoffs. These representations, which are tailored for irregular 3-D objects, store every input point exactly by using a tree structuring of the object space. Their advantage over more common representations is that they make perspective and hidden-surface elimination less difficult. In addition, one of the representations simplifies the storage of dynamic objects and objects with redundant sub-parts. (Author)

Interactive Generation of Object Models with a Manipulator

Abstract: Manipulator programs in a high-level language consist of manipulation procedures and object model declarations. As higher level languages are developed, the procedures will shrink while the declarations will grow. This trend makes it desirable to develop means for automating the generation of these declarations. A system is proposed which would permit users to specify certain object models interactively, using the manipulator itself as a measuring tool in three dimensions. A preliminary version of the system has been tested.

Object access serialization apparatus for a data processing system

Abstract: A serialization apparatus for a data processing system wherein access restrictions are automatically enforced: (1) in behalf of individual machine instructions in order to maintain object integrity; and (2) at each user's discretion in order to maintain synchronization among all concurrent users of any given object. Various types of restrictions can be enforced in behalf of both machine instructions and users, allowing concurrent access to objects at various levels where appropriate.

Methods and systems for three-dimensional measurement

Abstract: In a method for defining the spatial location of points comprising an object surface, pulsed radiant energy is projected onto the object surface and collections of object-reflected radiant energy are conducted separately in accordance with respective different time patterns which are mutually overlapping in time.

The effect of System Response Time on interactive computer aided problem solving

Abstract: The effects of System Response Time, SRT, on interactive graphical problem solving were investigated for fixed SRT's of 0.16, 0.72 and 1.49 seconds. The object was to demonstrate the importance or ...

System for positioning an object in an optical projection system

Abstract: The invention relates to the positioning of an object comprising at least two fixed reference marks in an optical projection system. The system according to the invention comprises two projector arms illuminating two regions of the surface of the object through two marks, which form a reference system, having a variable inter-axis interval, display means enabling coincidence between the reference marks of the object and the reference system to be established.

Examples for Change of Types and Object Structures

Abstract: The abstract, algebraic definition of data types by describing their properties forms a solid formal basis for the specification of computation structures independent of their particular representations. Thus programs can be designed and developed working with objects of an abstractly defined computation structure. The choice of particular representations (implementations), the releasing of this representation to the "outer world" and the consequences on further program development are demonstrated with examples of joint refinement.

Dynamic graphics using quasi parallelism

Abstract: Dynamic computer graphics is best represented as several processes operating in parallel. Full parallel processing, however, entails much complex mechanism making it difficult to write simple, intuitive programs for generating computer animation. What is presented in this paper is a simple means of attaining the appearance of parallelism and the ability to program the graphics in a conceptually parallel fashion without the complexity of a more general parallel mechanism. Each entity on the display screen can be independently programmed to move, turn, change size, color or shape and to interact with other entities.The scheme presented herein begins with the notion of a quantum of time, or tick, within which there are no ordering constraints on events. Each entity or actor decides what it must do upon the next tick. Ticks are a powerful means of controlling parallel processes but are usually at too low a conceptual level for user convenience. Higher-level operations built upon the tick mechanism are presented, most notably the ability to instruct any entity or group of entities to gradually change or move at a rate that is itself changeable by the same operation. To illustrate these ideas a simple celestial mechanics simulation is presented. Upon each tick the velocities and positions of the objects are updated by the gravitational and propulsive forces acting upon them.Ticks are only one product of an object-oriented programming style. For the best control and the most modularity, graphics programming should be object oriented. Each object displayed, and its parts, should be independently programable. Instead of being passive data, objects should be responsible for the changes in their position or appearance. Instead of a global controller, each object should interact with the others.

A Stochastic Search Game

Abstract: An object is hidden at a point e on the segment $[ {a,b} )$. A searcher tries to locate it by choosing points $x_i $ and asking: Is egreater than $x_i $ ?There is a positive probability of obtaining a wrong answer to these questions. The searcher wishes to locate the object in the smallest set possible in spite of the fact that some of the information that he has obtained may be false.

Method for detecting object picture by electron beam

Abstract: A method is disclosed in which an object picture such as an integrated circuit pattern is precisely and exactly detected at high speed by the use of an electron beam. At least two kinds of signals obtained by irradiating an object with an electron beam are detected and subjected to an adding/subtracting operation and a resulting signal is used to detect the object picture. Thus, a satisfactory S/N ratio can be obtained. The method is applicable to the inspection of a mask used for integrated circuits.

Picture retrieval ststem

Abstract: PURPOSE:To decrease the sheet number of the recording carrier to be the searching object and to facilitate an easy search for a large capacity picture, by minimizing the quantity of the index memory necessary for the searching index or changing the index memory into an easy-to-memorize naming for the human being.

Output correcting system for facsimile

Abstract: An optical image reading apparatus comprises a solid state image sensor having a plurality of blocks, means for generating video signals correponding to an object to be read out by the solid state image sensor, means for determining respective mean values of the video signals concerning the blocks, means for storing the mean values in digital information, means for reading out the stored mean value and converting the digital information to analog information, and means for determining a corrected slice level in each of the blocks.

Multiple-processor implementations of message-passing systems

Abstract: : The goal of this thesis is to develop a methodology for building networks of small computers capable of the same tasks now performed by single larger computers. Such networks promise to be both easier to scale and more economical in many instances. The mu calculus, a simple syntactic formalism for representing message-passing computations, is presented and augmented to serve as the semantic basis for programs running on the network. The augmented version includes cells, tokens, and semaphores, as well as primitives for side-effect-free computation. Tokens, a novel construct, allow certain simple communication and synchronization tasks without involving fully general side effects. The network implementation presented supports object references, keeping track of them by using a new concept, the reference tree. A reference tree is a group of neighboring processors in the network that share knowledge of a common object. Also discussed are mechanisms for handling side effects on objects and strategy issues involved in allocating computations to processors. (Author)

Object description with a manipulator

Abstract: This paper presents an interactive system, called POINTY. The goal of this system is to solve problems encountered when a high‐level manipulator lanaguage, as AL, is employed. Those problems are related to the necessity of supplying any manipulation program with a complete description of the objects involved. The object description has an important role in any task description oriented language. In these languages the procedural part, which expresses the assembly steps, is reduced by increasing correspondently the descriptive part, which expresses the knowledge a program has about the physical world. An approach to the generation of object models is presented, and the system based on it is illustrated. The basic idea is to point to the objects with the manipulator for building an incremental model of the world, and then to generate the AL corresponding instructions. The preliminary experiences using it demonstrate that the object model part of an AL program can be easily obtained and tested.

Operations data bases

Abstract: It is shown that the time dimension may be adequately incorporated in data models by distinguishing between object entity classes and process entity classes. Query language difficulties due to the time dependance of object entity attribute values are overcome by the introduction of the superschema or data supermodel concept. Queries for time decomposition of process instances, i.e. 'how-queries' are possible. However queries requesting the algorithmic decomposition of processes are possible if the data model is further expanded to permit inclusion of the algorithms governing the real world behaviour of the entities modelled in the data base. Three types of retrieval expression formats are presented: GET, GET-HOW, and GET HOW-COULD. Relational and extended owner-coupled set predicate calculus are used in the analysis.

Apparatus and method for moving a large object

Abstract: The method and apparatus for moving a large object using four crawler transporters disposed in a rectangular or a trapezoidal pattern under the object and which support and move the object with an effective three point suspension.

Autoidolon of Quasi-periodic Optical Objects

Abstract: In this paper the ability of quasi-periodic optical objects to form self-images is examined experimentally. The objects are transparencies consisting of different, but similar, patterns arranged periodically. The object transilluminated coherently forms in its diffraction light-field an autoidolon composed of identical images. The images are the common parts of the various patterns. Hence we have found that a self-imaging process can be used to extract the common part of the patterns.