SPI Common Extensions Manual

Glossary
SPI Common Extensions Manual—427508-001
Glossary-5
generic list
generic list. The most general list construct supported by SPI. It starts with ZSPI-TKN-LIST
and ends with ZSPI-TKN-ENDLIST. Generic lists can be nested. No Compaq
subsystem uses generic lists, but subsystems you write can do so. Compare with data
list and error list.
GETVERSION command. An information command that retrieves the server version of the
subsystem server and possibly additional version information about objects defined by
the subsystem. Every subsystem with an SPI command/response interface supports
the GETVERSION command.
header. See SPI message header.
header token. A special token, present in every SPI message, that provides information
about the message as a whole. The header tokens are typically items common to all or
most messages of a specific kind. Header tokens differ from other tokens in several
ways: they exist in the buffer at initialization, and their values are usually set by SSINIT;
they can occur only once in a buffer; they are never enclosed in a list, they cannot be
moved to another buffer with SSMOVE; and programs cannot position to them or
retrieve their values using the NEXTCODE or NEXTTOKEN operation. Programs
retrieve the values of header tokens by passing appropriate token codes to SSGET
and can change the values of some header tokens by passing their token codes to
SSPUT. Examples of header tokens for commands are the command, the object type,
the maximum-response token, the server-version token, the maximum-field-version
token, and the checksum token. Examples of header tokens for event messages are
the event number, the event generation time, the logging time, the maximum-field-
version token, and the checksum token.
header type. A header token in an SPI message that indicates whether the message is a
command or response message or an event message.
information command. A command that retrieves information about an object but does not
act on the object or change it in any way. Extended SPI classifies informational
commands as nonsensitive for security purposes. Compare with command
.
initial position. In an SPI buffer, the location just prior to the first token that is not a header
token. Compare with current-token position
and next-token position.
initialize. To prepare a data structure to have values assigned to it. For example, the SPI
SSINIT procedure initializes the buffer by building the message header; the SSNULL
procedure initializes an extensible structured token by assigning null values to the
fields of the structure.
is-present field. A field in a structure that indicates whether the value in a related field was
supplied by the program that sent the structure. In most cases, a field to which the
program made no assignment has the null value that was set by SSNULL. A
subsystem defines a separate is-present field when no null value can be defined that is
not a valid value for the field.