| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (3 out of 22)

Using System Tables

Every KB has one set of system tables in effect at a given time. G2 refers to these as the installed system tables.

In a new KB, the installed system tables contain the default values that G2 provides for each system table attribute. If you change one or more system table attributes and then save your KB, the modified system tables are saved as a permanent part of the KB's knowledge. G2 installs these system tables when next you load the KB.

If the current KB is modularized, indicating that it consists of one or more KB modules, each module has an associated set of system tables, though only one set is installed. Two reasons why modules include their own set of system tables are:

For a description of that system table, see Module Information.

You can replace one set of installed system tables with another by merging in a KB. If you merge a KB module into an existing KB, one of the options on the KB Merge menu is:

Choosing this option causes G2 to install the system tables of the merged KB, overriding those of the existing KB. The overridden system tables are still present in the KB, but their attributes are no longer in effect. You can search for system tables in your KB by using the Inspect facility. For more information on merging KB files with system tables, see Merging a KB File.

You can also start G2 with one or more optional command line options that let you specify a module map file or a module search path. Using either of these command line options can affect the values of the Module Information system table.

For information about using the module map file, or module search path command line options, see module-map and module-search-path. For a description of creating a module map file, see Using a Module Map File to Load and Save a KB.

Changing System Tables Interactively

To access the installed set of system tables:

This menu is displayed:


When you select a system table, G2 displays its attributes and the values for those attributes. Unlike most items, system tables are not associated with a workspace and display directly on the Gensym background area.

Changing System Table Values Programmatically

You can use the conclude action to change the value of most system table attributes. For example, to change the default font size for the Text Editor, enter a statement such as:

Information about the types and read and write access of system-defined attributes is available in the G2 Class Reference Manual.

| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (3 out of 22)

Copyright © 1997 Gensym Corporation, Inc.