Browse Prior Art Database

Reuse of Existing Subscription Specification Mechanism for Access to Historical Data

IP.com Disclosure Number: IPCOM000123390D
Original Publication Date: 1998-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 26K

Publishing Venue

IBM

Related People

Dixit, A: AUTHOR [+7]

Abstract

This disclosure relates to a method, in an Encina(*) Publish/Subscribe system, for using embedded "meta-information" in messages to allow a user to retrieve selected historical data.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Reuse of Existing Subscription Specification Mechanism for Access
to Historical Data

   This disclosure relates to a method, in an Encina(*)
Publish/Subscribe system, for using embedded "meta-information" in
messages to allow a user to retrieve selected historical data.

   The Publish/Subscribe system allows a subscriber to specify
the types of messages it wishes to receive via a "filter
specification".  The filter specification is a mathematical
predicate that is applied to the contents of each message.  A
message is delivered to the subscriber only if the predicate
evaluates to true for that message.

   By having the Publish/Subscribe system embed certain
"meta-information"--particular, timestamp and sequence number--in
the message contents, it becomes possible for a subscriber to
retrieve historical data by specifying a filter that compares the
timestamp or sequence number content of a message with a particular
constant value.

   The advantage of this approach is that no new interface is
necessary for retrieving historical data, and existing mechanisms
for reliably delivering current data can be reused for delivering
historic data.
  * Trademark of TRANSARC Corporation.