scanning: For a rule, the process of invoking the rule at some regular interval specified in the
Scan-interval attribute. Use scanning as a means of monitoring conditions in an application. scheduled drawing: One of two drawing modes. Scheduled drawing lets you control when KB drawing occurs. You can control KB drawing by calling the
g2-work-on-drawing system procedure from within any procedure where you want drawing to occur. Contrast with immediate drawing. scheduler: The part of G2 that directs all other processing. The scheduler works in clock ticks; within a single clock tick it does the following: schedules new tasks, runs tasks that have been scheduled (running a rule, for example), services external data servers, services the user interfaces, and services the simulator.
schematic: A picture of the application; consists of objects and their connections.
scope: For a configuration, the set of items to which the configuration pertains.
scrapbook workspace: A special workspace used for holding pieces of text used for insertion in the Text Editor.
secondary definition: When class definitions are merged, the definition that is merged into the primary definition.
secondary direct superiors: The second and later classes (if any) specified in a list of direct superior classes in a class definition. The first class in the list is called the primary superior class. All remaining classes in the list are secondary superior classes with a declining order of precedence.
secure G2: A G2 process that requires its users to log in. If the installed G2 product has a valid license, you run a G2 process that is secure by creating an authorization file (the
g2.ok file) and including it in entries for this G2's users. scrollable text editor: One of two interfaces to the G2 Text Editor, for editing attributes that typically have large amounts of text, such as procedures and methods. The scrollable editor allows you to scroll the contents of the editor's edit area and to enter newline characters more easily.
sequential execution: One of two methods of computational execution, the process of executing commands one after another, using the
in order statement. Each command completes before G2 continues to process the next. Contrast with concurrent execution. shallow simulation: A collection of simple heuristics that model observed behavior.
shrink wrapping: For a workspace, the operation of decreasing its extent, yet with its borders still outside those items upon the workspace that are farthest apart vertically and horizontally.
simple attribute: An attribute that is neither given by a parameter or variable, nor by an instance of a class. A simple attribute can have values of any type. No type-checking occurs.
simulation formula: For a variable, a formula entered in the
Simulation formula attribute of its simulation subtable, which the simulator uses to calculate a value. simulation procedure: A procedure that the simulator calls either when the application is initialized or once each simulation cycle. Although there is no separate subclass of procedure used specifically for simulation, a simulation procedure behaves in a slightly different manner from other procedures.
simultaneous execution: See concurrent execution.
single inheritance: In object-oriented programming, the practice of allowing a class to have only one direct superior class.
single inheritance class: A class that neither has, nor inherits any class that has, more than one parent.
source G2: For a remote procedure call, the G2 from which a remote procedure call originates. Contrast with target G2.
specific formula: For a variable, a formula entered in its
Formula attribute to calculate a value for a specific variable. G2 evaluates a specific formula as a result of data seeking. A specific formula overrides any generic formulas for the variable, and requires that the data server be the inference engine. Contrast with generic formula. spreadsheet format: A GFI file format in which data is stored in rows and columns that resemble the layout of a spreadsheet.
stable-for-dependent-compilations: One of two G2 compilation configurations. This configuration declares that an item is not subject to further change, and allows G2 to compile more efficiently other items that refer to the configured item. Contrast with independent-for-all-compilations.
standard characters: Letters, digits, hyphens, underscores, apostrophes, and periods.
standard output messages: A report of the initial allocations for G2's memory regions and network port numbers. As a new G2 process starts up, it displays standard output messages. A G2 process also produces standard output messages when it must attempt to allocate additional memory allocations and when it detects an internal error.
state variable: A variable that depends on its own previous value. In G2, state variables are explicitly created only within simulation formulas.
statement: A rule, a regular formula, a simulation formula, a user-defined function, or an executable instruction in the body of a procedure.
status: One of several pieces of knowledge that an item contains, about its ability to participate in the current KB's processing. An item's statuses are permanent/transient, active/inactive, enabled/disabled, and OK/bad/incomplete. An item's statuses are distinct from its attributes, though G2 reports item statuses in an item's
Notes attribute. Status Indicator: In the Icon Editor, a display that shows various message that describe the current state of the editor or prompt for user input.
stubs: An extendable connection segment at the edge of an object. Object definitions define the number, appearance, and placement of connection stubs on a class of objects. You can also add and delete stubs for individual objects.
subattribute: An attribute that is part of another attribute's value. For example, History-keeping-spec of a variable or parameter has three subattributes:
maximum-number-of-data-points
maximum-age-between-data-points
minimum-interval-between-data-points
the minimum-interval-between-data-points of the history-keeping-spec of x
subexpression: An expression that is a term of another expression.
subobject: The object contained in the attribute of an item.
subtable: The attribute table of any subobject.
subworkspace: A workspace that is subordinate to an item. Only items of certain classes can have a subworkspace, and an item of the proper class can have only one subworkspace. A subworkspace can be affected by the
activatable-subworkspace configuration property on its superior item. (See activatable subworkspace.) Contrast with top-level workspace. superior class: A class that is at a higher level than another in the hierarchy of classes. Classes inherit attributes from their superiors.
symmetric relation: A relation definition whose
Relation-is-symmetric attribute contains the symbol yes. This means that concluding a relation of this kind also concludes an inverse relation of the same name and kind. system-defined attribute: An attribute provided by one of G2's system-defined classes. Contrast with user-defined attribute.
system-defined class: A class that G2 provides by default, and which is a member of the default class hierarchy. For example,
OBJECT, VARIABLE, PROCEDURE, and RULE are system-defined classes. You cannot remove a system-defined class from G2. Contrast with user-defined class.