SPI Common Extensions Manual

Glossary
SPI Common Extensions Manual—427508-001
Glossary-2
context information
context information. The information required by a subsystem to continue processing a
command for which a partial response was returned. Continuation of a response in
multiple response messages requires the subsystem to send context information to the
requester. The application program, in turn, must return that information to the
subsystem in a new command message so that the subsystem can continue
processing. See context token.
context token. A token that indicates (by its presence or absence) whether or not a
subsystem has more objects to process or more response messages to return. If this
token is present in a response message, the response is incomplete and can be
continued in another response message. To obtain the next message, the requester
reissues the original command with the context token. When the server returns a
message that does not contain a context token, the requester knows that the response
is complete.
context-free server. A server that does not retain any information about command
processing after returning a response. A context-free server stores any information it
needs to continue processing an incomplete command in the context token, which it
returns to the requester. The requester must resend the command with the context
token for the server to continue processing. A context-free server allows the requester
to interrupt or abandon the continuation of a series of response messages.
context-sensitive server. A server that retains information about previous processing. For
instance, in performing a command on a list of objects, a context-sensitive subsystem
might retain, between response messages, the name of the object it last processed.
Context-sensitive servers limit or complicate the requester's ability to interrupt or
abandon the continuation of a series of response messages.
continuation. A method of completing a response in multiple response messages. The
subsystem uses a context token to indicate that the response is continued to another
message. Each response message can contain multiple response records.
control and inquiry. Those aspects of object management related to the state or
configuration of an object. Such aspects include actions that affect the state or
configuration of an object, inquiries about the object, and commands pertaining to the
session environment (for example, commands that set default values for the session).
Compare with event management.
control operation. An action that affects the recording, processing, transmission, or
interpretation of data. In SPI, an operation that modifies the contents of an SPI buffer
not by adding a token but by performing a housekeeping function; for instance, clearing
the last SPI error number or flushing the buffer from the current position. A positioning
operation is one kind of control operation.
current token. The token in the current position. See current-token position.