wiki:IpaacaTutorial

Version 1 (modified by yaghoubzadeh, 6 years ago) (diff)

initial version - incomplete - working on it later :)

ipaaca Development Tutorial

INCOMPLETE - in progress

Basic definitions

IUs and Messages

The basic unit of information transmitted (shared) in the ipaaca system is the Incremental Unit (IU). An IU is an object characterized by the following basic attributes:

  • uid - a globally unique identifier
  • category - a string representing the broad category of data, e.g. "asrresults" for transmitting the results of ASR
  • owner - the buffer name (see below) that initially produced this IU
  • payload - the IU payload: a hash of string->string, free to use by the application
  • links - a hash of string->string, representing the links of the IU (see below)

IUs are persistent objects. That means that they can be modified at any time (unless specified as read-only by the user), and any changes of published IUs are automatically transmitted as updates to all relevant parties. They can also be modified from the remote side, unless specified otherwise.

The Message is a special case of an IU: it is a non-persistent read-only version of the IU. It can be used whenever you just want to send current information (akin to lightweight message-passing systems, hence the name), without the possibility of later modification. The benefit is that Messages are only present for the time of reception and do not occupy additional cumulative recources.

Buffers

IUs are objects that exist in Buffers. A program can have any number of OutputBuffers and InputBuffers. When a new IU has been created, it has to be placed in an OutputBuffer. It is thereby published.

InputBuffers that components have initialized have a list of category interests, set by the user. Whenever an IU (or Message) of said categories is published or modified anywhere on the system, the corresponding InputBuffers will receive a notification of this, along with the updated IU contents.