Galaxy Communicator Documentation:
Glossary
broker
A server-to-server connection, unmediated by the Hub, through
which typed data can be transmitted.
broker proxy
An encapsulation of the connection and type information associated
with a broker.
call environment
A structure passed to every dispatch function which contains the
environment of the invocation, such as the current session, the connection
through which the message was received, and whether or not a response has
been provided yet.
dispatch function
A procedure invoked in a server in response to a rule
in a Hub program.
environment
See call environment.
frame
A general-purpose data object which is passed between servers
and the Hub. It consists of a frame type, a frame name, and a collection
of attributes, or keys, and their associated values. See the frame documentation.
global variables, program file
See program file
global variables.
Hub
An executable which controls the interaction among a number of
servers, using a Hub script as its controller.
Hub script
Initialization file for the Hub which contains information
about available servers (name, location, externally accessible operations),
global variables, and possibly flow of control instructions. Also known
as a program file.
Hub program
A set of rules that describes a sequence of operations
specifying the flow of control in the Hub.
initial token
A token specified in the program file which is executed
immediately after the Hub contacts its servers.
key-value pair
An attribute and its associated value that describes some domain
entity. Sets of key-value pairs are stored in frames.
logfile
Text file containing logs of timestamped server operations and
specified key values.
message
A frame used as a vehicle for communication to and from servers.
The key-value pairs which comprise the message sent to the server are drawn
from the Hub program rules and the current state of the token.
The message causes a dispatch function to be invoked in the server.
Any response from the dispatch function is used to update the token state.
See frame, token.
namespace
One of five types of frames comprising a memory state during
the execution of a Hub program.
operation
A dispatch function supported by a server, as viewed
by a service type in a program file.
program, Hub
See Hub program.
program file
See Hub script.
program file global variables
Program file declarations used to set key-value pairs in the initial
token and to set global information about the Hub. Examples include
DOMAIN:, USER_ID:,LOG_DIR:.
provider
See service provider.
provider ID
A bracket-delimited string enclosing an integer or string which
comprises the obligatory portion of a provider name.
provider name
A unique string, consisting of a provider ID and an optional
service type, which names a service provider in a Hub
script.
rule
An element of a Hub program which specifies a condition
for execution and instructions for constructing a message to a server
and for updating the state of the token.
scripted interaction
A new incoming message which the Hub processes according to the
instructions in a Hub program whose name matches that of the incoming
message.
scriptless interaction
A new incoming message which the Hub processes by dispatching
directly to a server which supports a dispatch function whose name
matches that of the incoming message.
scripting module
A module compiled into the Communicator Hub which assumes responsibility
for the processing of a subset of incoming new messages. MIT provides the
default scripting module, which allows users to specify programs to
implement this control.
server
An executable configured to accept messages from the Hub
and respond to dispatch functions invoked by these messages.
server-to-server subdialogue
A call to GalSS_EnvDispatchFrame, which uses the Hub to invoke
operations on another server or servers and retrieves the result. The Hub
may retrieve this information via a Hub program, or it may relay the request
directly to another server.
service provider
A specific process on a specific host which qualifies as an instance
of a service type.
service type
A named collection of operations in a program file.
Each operation is expected to correspond to a dispatch function implemented
by any service provider which is an instance of this service type.
session
An instance of an interaction of a user with a Hub.
token
A frame which represents the evolving state of the execution of
a Hub program. A token is similar to the local memory state of
a function or a procedure. See also frame, message.
utterance ID
Internal counter maintained by the builtin server. This
counter can be updated only by calling builtin.increment_utterance.
This counter cannot currently be accessed except by calling this builtin
function.
verbosity
A setting provided to a Hub or server which controls the amount
of information printed out. Zero verbosity is silence; the highest level
of verbosity is 6; the default is 3.
Last updated August 13, 2002