## Chapter 7. Glossary

Some of the definitions in this glossary are taken from the IBM Dictionary of Computing, ZC20-1699.

A
accelerator | A keystroke sequence that reduces the number of steps needed to complete a task.
anchor window | The window in which a Data Explorer session starts (either the Visual Program Editor or the Image window). The window is identified by an anchor symbol in the top left corner. When this window is closed, the Data Explorer session ends.
array | In Data Explorer, an array structure containing an ordered list of data items of the same type along with additional descriptive information.
B
Browser | A Data Explorer user interface for determining the layout and organization of data in a file.
C

camera

An object that describes the viewing parameters of an image (e.g., width of the viewport, viewer's location relative to the object, and the resolution and aspect ratio of the image). A camera may be explicitly defined and passed as a parameter to the Render or Display module. It may also be implicitly defined in the use of interactive, mouse-driven options (such as zoom or rotate) in the Image window.

canvas | The area of a VPE window used in building and editing visual programs.
cell-centered data | See connection-dependent data.
clipping plane | A plane that divides a 3-dimensional object into a rendered and an unrendered region, making the object's interior visible.
colormap | In Data Explorer, a color map that relates colors to data values. The colors are carried in the map's "data" component and the data values to which each color applies in its "positions" component.
Colormap Editor | A Data Explorer user interface for mapping precise colors to specified data values, the results of which are displayed in a visual image.
component | A basic part of a field (such as "positions," "data," or "colors"); each component is indexed by a string (e.g., "positions"), and its value is typically an array object (e.g., the list of position values).
connection | Component of an IBM Data Explorer data field that specifies how a set of points are joined together. Also controls interpolation.
connection-dependent data | Cell-centered data. The data value is interpreted as constant throughout the connection element.
contour | On a surface, a line that connects points having the same data value (e.g., pressure, depth, temperature).
control panel | A Data Explorer interactive window that facilitates setting and changing the parameters of visual programs.
cube | A volumetric connection element that connects eight positions in a data field.
cutting plane | An arbitrary plane, in 3-dimensional space, onto which data are mapped.
D
data-driven interactor | Interactors whose attributes (such as minimum and maximum) are set by an input data field.
Data Prompter | A graphical user interface that enables a user to describe the format of the data in a file. The prompter creates a General Array Format header file that is used by the Import module to import the data.
dialog box | The "window" displayed when the user selects a pull-down option that offers or requires more detailed specification.
display | (1) v. To present information for viewing, usually on a terminal screen or a hard-copy device. (2) n. A device or medium on which information is presented, such as a terminal screen. (3) Deprecated term for panel.
Display module | A non-interactive module for displaying an Image. See Image window.
E
element | See connection.
executive | The component of the Data Explorer system that manages the execution of specified modules. The term often refers to the entire server portion of the Data Explorer client-server model, including the executive, modules, and data-management components.
F
field | A self-contained collection of data items. A Data Explorer field typically consists of the data itself (the "data" component), a set of sample points (the "positions" component), a set of interpolation elements (the "connections" component), and other information as needed.
G
general array format | A data-importing method that uses a header file to describe the data format of a data file. This "format" makes it possible to import data in a variety of formats.
glyph | A graphical figure used to represent a particular variable. Each occurrence of a glyph represents a single value of the associated variable. Some attribute of the glyph (e.g., length or angle) is a function of the variable and varies with it.
group | A collection of objects.
I
icon | A displayed symbol that a user can point to with a device such as a mouse to select a particular operation or software application.
Image window | IBM Data Explorer window that displays the image generated by a visual program. Associated with the Image window are special interactors for 3-D viewing.
interactor | A Data Explorer device used to manipulate data in order to change the visual image produced by a program. See also data-driven interactor, interactor stand-in.

interactor stand-in

An icon used in the VPE window to represent an interactor. Stand-ins are named after the type of data they generate:

- integer
- scalar
- selector (outputs a value and a string)
- string
- value
- vector.

interpolation element | An item in the connections component array. Each interpolation element provides a means for interpolating data values at locations other than the specified set of sample points. See positions component.
invalid | A classification of an array item (typically positions or connections). An invalid item is not rendered or realized.
isosurface | A surface in 3-dimensional space that connects all the points in a data set that have the same value.
isovalue | The single value that characterizes each and every point constituting an isosurface. By default, this value is the average of all the data values in the set being visualized.
item | A single piece of data in an array.
L
line | An element that connects two positions in a field.
M
macro | In IBM Data Explorer, a sequence of modules that acts as a functional unit and is displayed as a single icon. Macros can also be defined in the Data Explorer scripting language.
menu bar | In windows, a horizontal bar that displays the names of one or more menus (or tasks). When the user selects a menu, a pull-down list of options for that menu is displayed.
module | (1) In IBM Data Explorer, a primitive function, such as Isosurface. (2) In a VPE window, the icon for a module (also called a tool, q.v.). (3) A program unit that is functionally discrete and identifiable (i.e., it can be assembled, compiled, combined with other units, and so on).
N
navigate | To move the camera (changing the "to" and "from" points) around the image scene, using the mouse.
netCDF | See Network Common Data Form.
network | In Data Explorer the set of tool modules, interactor stand-ins, and connections that constitute a visual program. In the VPE window, a network appears as a set of icons connected by arcs.
Network Common Data Form (netCDF) | A data format that stores and retrieves scientific data in self-describing, multidimensional blocks (netCDF is not a database management system, however). netCDF is accessible with C and FORTRAN.
O
object | In IBM Data Explorer, any discrete and identifiable entity; specifically, a region of global memory that contains its own type-identification and other type-specific information.
opacity | The capacity of matter to prevent the transmission of light. For a surface, an opacity of 1 means that it is completely opaque; an opacity of 0, that it is completely transparent. For volume, opacity is defined as the amount of attenuation (of light) per unit distance.
P
palette | A displayed grouping of available selections (such as functions, modules, or colors) in a GUI window.
palindrome | In Data Explorer, a mode of running a sequence of images in one direction and then in the opposite direction.
pixel | Picture element. In computer graphics, the smallest element of a display surface that can be independently assigned color and intensity.
position-dependent data | Data that are in one-to-one correspondence with positions.
positions component | A component that consists of a set of dimensional points in a field.
probe | A list of one or more vectors that represent points in a graphical image. Probes can be used with Data Explorer tools that accept vectors as input (such as ClipPlane and Streamline) or to control the view of an image.
pull-down | In windows, the list of options displayed when a task is selected from the menu bar.
Q
quad | An element that connects four positions in a field.
R
realization | A description of how raw data is to be represented in terms of boundaries, surfaces, transparency, color, and other graphical, image, and geometric characteristics.
rendering | The generation of an image from some representation of an object, such as a surface, or from volumetric information.
ribbon | A figure derived from lines (e.g., from streamlines and streaklines). Ribbons may twist to indicate vorticity.
S
sample point | A point that represents user data. Data is interpolated between sample points by interpolation elements (connections).
scalar | A non-vector value characterized by a single, real number.
scatter data | A collection of sample points without connections.
scripting language | The IBM Data Explorer command language. Used for writing visual programs, to manage the execution of modules, and to invoke visualization functions.
scroll | To move all or part of the display image vertically or horizontally to display data that cannot be observed in a single display image.
Sequencer | An IBM Data Explorer tool for creating "animated" sequences of images.
series | In IBM Data Explorer, used to represent a single field sampled across some parameter (e.g., a simulation of a CMOS device across a temperature range).
stand-in | See interactor stand-in.
streaklines | Lines that represent the path of particles in a changing vector field. Also called rakes.
streamlines | Lines that represent the path of particles in a vector field at a particular time. Also called flow lines.
T
tetrahedron | A volumetric connection element that connects four positions in a field.
tool | In IBM Data Explorer, a general term for any icon used to build a visual program (specifically, module, macro, or interactor stand-in).
triangle | A connection element that connects three positions in a field.
tube | A surface centered on a deriving line (e.g., a streamline or streakline). Tubes may twist to indicate vorticity.
V
vector | A quantity characterized by more than one component.
vertex | One of the positions that define a connection element.
visual program | A user-specified interconnected set of Data Explorer modules that performs a sequence of operations on data and typically produces an image as output.
Visual Program Editor (VPE) | IBM Data Explorer window used to create and edit visual programs and macros. See also canvas.
volume | The amount of 3-dimensional space occupied by an object or substance (measured in cubic units). To be distinguished from an object's surface, which is a mathematical abstraction.
volume rendering | A technique for using color and opacity to visualize all the data in a 3-dimensional data set. The internal details visualized may be physical (such as the structure of a machine part) or they may represent characteristics (such as fluid flow, temperature, or stress).
vorticity | Mathematically defined as the curl of a velocity field. A particle in a velocity field with nonzero vorticity will rotate.
VPE | See Visual Program Editor.

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