Assigning Hierarchical Descriptions to Visual Assemblies of Blocks with Occlusion

This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0643.This memo describes a program for parsing simple two-dimensional piles of blocks into plausible nested subassemblies. Each subassembly must be one of a few types known to the program, such as stack, tower, or arch. Each subassembly has the overall shape of a single block, allowing it to behave as part of another subassembly. Occlusion is represented by an area of the image plane whose contents cannot be seen. Heuristic aspects of the program are concerned with 1) ambiguity among competing subassemblies due to sloppiness of the placement of the blocks, 2) ambiguity due to uncertain measurements of blocks which are partially occluded, and 3) total ambiguity as to the contents of the occluded region. Choice among competing subassemblies is accomplished by first making a topological description of the network of conflicts among subassemblies, then considering only the simplest competing subset. If this does not clearly indicate a winner, the system can make an in-depth comparison of the internal structures of the last two competing subassemblies. Uncertainty as to measurements of blocks is handled by creation of a disjunction of more certain blocks, each of which participates in the parsing process. If this disjunction results in a pair of competing subassemblies, only one is used, the other being hidden as an alternate to the first, so that the choice of which will be accepted can be deferred. This is a deferrable choice because the alternate subassemblies are so closely similar that the parsing process does not depend on choosing one of them. Uncertainty due to occlusion is handled by allowing a potential subassembly to use the occluded area as a "wild card", meaning that if the subassembly can be completed by creating a block which intersects the occluded area, it is so completed. Such an imaginary block may later be consolidated with a real one, or it may remain imaginary. The reason for studying this problem is to become acquainted with the program and data structure needed to assign a nested structural description to a complicated visual assembly in which occlusion makes the data incomplete. The extension to 3-dimensional descriptions should be straightforward.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

Knowledge About Interfacing Descriptions

Work reported herein was conducted at the Artificial Intelligence Laboratory, a Massachusetts Institute of Technology research program supported in part by the Advanced Research Projects Agency of the Department of Defense and monitored by the Office of Naval Research under Contract Number N00014-70-A-0362-0005.This concentrates on interactions between knowledge stated in diverse representations. It proposes a vision program that classifies any complicated object as an elaborated instance of a simple on it already understands. The resulting global-local connections facilitate evaluation of overall properties, such as visual shape and ability to support other objects. Flexibility is achieved through simultaneous use of multiple equivalent representations. These are coordinated via interfacing rules for giving hints, constraining choices, and filling in missing detail, making use of the great redundancy in most visual scenes. An important feature of the system consists of domain-dependent rules for guiding the flow of control and choosing hypothesis.MIT Artificial Intelligence Laborator

Hierarchy in Descriptions

Work reported herein was conducted at the Artificial Intelligence Laboratory, a Massachusetts Institute of Technology research program supported in part by the Advanced Research Projects Agency of the Department of Defense and monitored by the Office of Naval Research under Contract Number N00014-70-A-0362-0005. Vision Flashes are informal papers intended for internal use.Organization of knowledge requires the flexible use of hierarchy in descriptions. This memo attempts to catalog the issues related to recognizing and executing such descriptions, drawing examples primarily from the blocks world.MIT Artificial Intelligence Laboratory Robotics Sectio

Control, Multiple Description, and Purpose in the Visual Perception of Complex Scenes: A Pogress Report

This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0643.This memo describes a vision program for recognizing simple furniture comprising assemblies of blocks, in which the same item may be composed in diverse ways. As such, it is concerned with three theoretical issues, perceptual processing, supression of unwanted detail, and segregation and interconnection of information. The program's perceptual processing relies on an elaborate, redundant, alterable model of the scene rather than on any clever process structure. This approach aids the interpretation of incomplete, ambiguous portions of the scene as well as simplifies the program. The model is capable of quantitative as well as qualitative alteration, by a constraint-propogation system and a system of frame-shift demons. The hierarchical nature of the scene - assemblies of assemblies of blocks - is reflected as hierarchy in the model. Each assembly is represented as having an external aspect, by which it relates to surrounding assemblies, and an internal aspect, listing the parts and relationships composing it. This imposes a natural supression of detail. In addition to the vertical layering of the model there are horizontal subdivisions adapted for different computational purposes. There is a 2D section representing the image, a 3D section representing the shape, and a stability section representing the physical forces and moments acting upon each unit. Each of the sections can be used through any of several indirect reference frames corresponding to different spatial viewpoints. Many computations on the model, such as stability analysis, spatial relationships, and visual matching, are greatly simplified by first selecting the proper spatial viewpoints.MIT Artificial Intelligence Laborator

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.Comment: To be published in At. Data Nucl. Data Table

1966

Proper Watering by Earl P. Grey (page 1) Soil Structure and Plant Feeding for Trees and Shrubs on the Golf Course by William Teece (2) Power Golf Carts: A Blessing or a Curse by David Dunlavey (3) A Comparison by Paul White (3) Trees on a Golf Course by Oliver Leech (5) Turf Management Majors Want a Golf Team by Richard Rossiter (6) Class Will of \u2766 (7)Famous Last Words from 1966 (8) Turf Heating with Electric Cables by J.R. Barrett, Jr. and W.H. Daniel (A-1) Poa Annua Restriction by C. F. Kerr and W.H. Daniel (A-9) Phosphorus by Marvin H. Ferguson (A-14) Role of Potassium in Turf Grass management by R. E. Wagner (A-16) Role of Minor Elements in Turfgrass Management by Alexander Radko (A-22) Rhizoctonia Brown patch and Pythium Diseas by Malcolm C. Shurtleff (A-27) Sclerotinia Dollar Spot and Snow Mold by Noel Jackson (A-32) Fusarium Blight - Disease of Turf Grasses by George A. Bean (A-35) Observing the Weather - Old and New Techniques by Robert C. Copeland (A-39) Water Supply by Allan Grieve Jr. (A-41) Establishment and Maintenance of Campus Turf by William A. Lambert (A-51) Athletic Field Management by J. T. Williams (A-56