Browse Prior Art Database

Event Data Management in an Object Oriented System

IP.com Disclosure Number: IPCOM000116914D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 246K

Publishing Venue

IBM

Related People

Chen, C: AUTHOR [+4]

Abstract

A method of managing event data in a real-time system developed using a hybrid Object Oriented Analysis (OOA) methodology is disclosed. This system is an event-driven system. An event causes a specific state transition of an object as well as execution of a corresponding state action. An event can simply be a message with a fixed format that is known by the object which is capable of sending/receiving events. An event can also 'carry' additional information as supplemental event data. An Event Data Type (EDT) defines the total number of event data fields and the data type of each field.

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Event Data Management in an Object Oriented System

      A method of managing event data in a real-time system developed
using a hybrid Object Oriented Analysis (OOA) methodology is
disclosed.  This system is an event-driven system.  An event causes a
specific state transition of an object as well as execution of a
corresponding state action.  An event can simply be a message with a
fixed format that is known by the object which is capable of
sending/receiving events.  An event can also 'carry' additional
information as supplemental event data.  An Event Data Type (EDT)
defines the total number of event data fields and the data type of
each field.

In an object oriented system, event data is handled under the
following constraints:
  1.  An event must always be sent with exactly the same event data
       even if it causes different state transitions in different
       objects.
  2.  All the events that cause state transitions to the same state
       must be sent with exactly the same Event Data Type (EDT).  In
       other words, the state actions associated with the target
state
       should not care about which event causes the state transition.

      In order to support the event data management complying with
the constraints as stated above, several key issues need to be
resolved:
  1.  A 'supertype event' can be sent to different subtype objects;
       that is, it can show up in different state models.  How can it
be
       guaranteed to use the same EDT across its subtypes' state
models?
  2.  How can the state actions associated with a state not care
about
       which event causes the state transition and still be able to
       access the event data that is sent with the event?
  3.  What is the scope of an EDT?
  4.  How is the binding between EDTs and events identified and
       defined?
  5.  How is the binding between EDTs and states identified and
       defined?

      A description of a working implementation that provides event
data management for an object oriented system is presented.  The key
factors to event data management are:
  1.  Establishing strong naming conventions throughout the system.
  2.  Using the concept of Relative Event Number (REN).  For more
       information on REN, please refer to the disclosure, Algorithm
to
       Optimize State Transition Data Structures Associated with
       Supertype Events.
  3.  Identifying the total number of EDTs required for each
       supertype/subtype hierarchy.
  4.  Identifying the binding between EDTs and events/states.
  5.  Keeping the name symbols used by EDTs as stable as possible.

      In an object oriented system, only active objects can send or
receive events.  An EDT defines the total number of event data fields
and the data type of each field.  An EDT is a relatively 'generic'
entity within the scope of an acti...