element index: A numeric value specified within square brackets, used as a positional reference to a list or array element.
encapsulation: In object-oriented programming, the technique of including in an object and its context the knowledge of how to perform an operation on that object, rather than in the code that invokes the operation.
error condition: An unexpected discrepancy that occurs while G2 is handling information.
error handler: The portion of an application that responds to error conditions. G2 provides a default error handler, which responds to an error condition by placing a message on the Operator Logbook. You can write a custom error handler in a G2 procedure by coding an
on errorstatement whose block of statements respond to error conditions that arise within that procedure.
evaluation attributes: A special type of attribute that controls the way G2 evaluates expressions. Evaluation attributes are currently used only in freeform tables.
event: A system-defined occurrence. The antecedent of a
wheneverrule can refer to events.
event detection: G2's activity of invoking certain rules after detecting an event.
event log format: A GFI file format in which data is stored in rows. Each row contains a time-stamp, a variable or parameter name, and a value.
event-driven: Acting in response to events. Forward chaining is one kind of event-driven processing, where G2 invokes certain rules after detecting new knowledge.
exceptional float values: Values of type
floatthat represent the values negative infinity (
-Inf), positive infinity (
+Inf), and not a number (
NaN). Using these values in an arithmetic expression produces another exceptional float value.
expiration time: The time when the value of a variable will expire. This is calculated for all values of variables and displayed in the attribute table.
explicit time-stamp: A GFI time-stamp format in which a date and time are explicitly listed.
expression: A phrase that G2 evaluates to produce a value or a reference to an item.
extensible class: A class that can be the direct superior class of a user-defined class.
extent: The visible, rectangular portion of a workspace. Also, the visible, rectangular region within which G2 displays an item's representation.
external interface: An interface between G2 and external systems.
external variable: A kind of object in the external system to which data is sent or from which a GSI (G2 Gateway) variable receives data.