PUBLISH/SUBSCRIBE SYSTEM AND METHOD FOR MANAGING SUBSCRIPTIONS

• US 20070088711A1
• Filed: 10/17/2006
• Published: 04/19/2007
• Est. Priority Date: 10/19/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: CRAGGS, IAN
• Granted Patent: US 8,849,754 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06Q 10/10 Office automation; Time management

Abstract

In a publish/subscribe system, a plurality of publishers provide information on a range of topics and a plurality of subscribers subscribe to one or more topics and topic sets on which they wish to receive information. Subscribers can also unsubscribe from topics and topic sets on which they do not wish to receive information. A subscription matcher such as a message broker is used to generate a subscription list of topic and topic set identifiers—from both the subscribe and unsubscribe requests of each subscriber. The subscription matcher then matches items of information from each publisher with topics and topic set definitions in the subscription list of each subscriber, and distributes matched items of information in accordance with subscription lists. The subscription matcher determines precedence between any overlapping subscribed and unsubscribed topics and topic sets based on the sequence in which they were stored.

Claims

1. A method for managing subscriptions to topics and topic sets in a publish/subscribe system, wherein subscriptions indicate information topics of interest to subscribers and are used to identify published information that should be passed to subscribers, the method comprising:

in response to a subscriber'"'"'s subscribe request identifying a first topic or topic set, storing an identifier of the first topic or topic set as a positive subscription;

in response to an unsubscribe request for the subscriber, which unsubscribe request identifies a second topic or topic set that comprises a partial overlap of the identified topic or topic set of the positive subscription, storing an identifier of the second topic or topic set as a negative subscription; and

comparing topics of received publications with stored identifiers of topics and topic sets of both the positive and negative subscriptions, to determine which publications should be passed to the subscriber.

2. The method of claim 1, wherein the identifier of the second topic or topic set is stored as a negative subscription if the second topic or topic set is any one of a superset, a subset and a partially overlapping set of the first topic or topic set;

and wherein the identifiers of the first and second topic or topic set are deleted if the second topic or topic set is an identical match for the first topic or topic set.

3. The method of either claim 1 or claim 2, wherein the comparing step determines the precedence of said stored positive and negative subscriptions such that more recently stored identifiers take precedence over less recently stored identifiers.

4. The method of claim 3, wherein the identifiers of topics and topic sets are stored in the order in which the subscribe and unsubscribe requests are received, and the comparing step compares topics of received publications with stored identifiers of topics and topic sets in a sequence which is the reverse of the sequence in which they were stored, and disregards any topics identified within positive subscriptions that are cancelled by more recently stored negative subscriptions.

5. The method of claim 4, further comprising the step of:

in response to an unsubscribe request for the subscriber, determining whether any topic or topic set of a positive subscription is included in a newly unsubscribed topic set and, if so, removing the corresponding topic identifier from the stored topic identifiers; and

wherein said step of storing an identifier of the second topic set as a negative subscription is only performed when the second topic set comprises a subset of the identified topic set of a positive subscription.

6. The method of claim 5, further comprising the step of:

in response to a request from a subscriber to subscribe to a topic set, determining if any stored topic identifier of a current positive subscription is included in a newly subscribed topic set and, if so, replacing the stored topic identifier with the topic set identifier.

7. The method of claim 6, further comprising the step of:

in response to a request from a subscriber to subscribe to a topic or topic set, adding an identifier of the topic or topic set to the stored positive subscriptions if the topic or topic set is not already identified in a stored positive subscription, or if the requested topic or topic set overlaps a topic or topic set of a stored negative subscription.

8. A message broker for brokering published information and subscriber requests in a publish/subscribe system, the system comprising a plurality of subscribers that are each capable of requesting to subscribe to one or more topics and topic sets on which it wishes to receive information and to unsubscribe from topics and topic sets on which it does not wish to receive information, and a plurality of publishers for providing information on a range of topics, the message broker comprising:

(a) means for performing subscription management steps including;

(i) in response to a subscriber'"'"'s subscribe request identifying a first topic or topic set, storing an identifier of the first topic or topic set as a positive subscription, and (ii) in response to an unsubscribe request for the subscriber, which unsubscribe request identifies a second topic or topic set that comprises a partial overlap of the identified topic or topic set of the positive subscription, storing an identifier of the second topic or topic set as a negative subscription; and

(b) means for comparing topics of received publications with stored identifiers of topics and topic sets of both the positive and negative subscriptions, to determine which publications should be passed to the subscriber; and

(c) means for passing a publication to a subscriber in response to the means for comparing determining that a publication should be passed to the subscriber.

9. A computer program product comprising computer usable media embodying program instructions which, when executed by a computer results in the computer executing a method for managing subscriptions in a publish/subscribe system wherein subscriptions indicate information topics of interest to subscribers and are used to identify published information that should be passed to subscribers, said method comprising the steps of:

in response to a subscriber'"'"'s subscribe request identifying a first topic or topic set, storing an identifier of the first topic or topic set as a positive subscription;

in response to an unsubscribe request for the subscriber, which unsubscribe request identifies a second topic or topic set that comprises a partial overlap of the identified topic or topic set of the positive subscription, storing an identifier of the second topic or topic set as a negative subscription; and

comparing topics of received publications with stored identifiers of topics and topic sets of both the positive and negative subscriptions, to determine which publications should be passed to the subscriber.

10. The computer program product of claim 9 wherein the identifier of the second topic or topic set is stored as a negative subscription if the second topic or topic set is any one of a superset, a subset and a partially overlapping set of the first topic or topic set;

and wherein the identifiers of the first and second topic or topic set are deleted if the second topic or topic set is an identical match for the first topic or topic set.

11. The computer program product of either claim 9 or claim 10 wherein the comparing step determines the precedence of said stored positive and negative subscriptions such that more recently stored identifiers take precedence over less recently stored identifiers.

12. The computer program product of claim 11 wherein the identifiers of topics and topic sets are stored in the order in which the subscribe and unsubscribe requests are received, and the comparing step compares topics of received publications with stored identifiers of topics and topic sets in a sequence which is the reverse of the sequence in which they were stored, and disregards any topics identified within positive subscriptions that are cancelled by more recently stored negative subscriptions.

13. The computer program product of claim 12 further comprising a program instruction for causing performance of the step of:

in response to an unsubscribe request for the subscriber, determining whether any topic or topic set of a positive subscription is included in a newly unsubscribed topic set and, if so, removing the corresponding topic identifier from the stored topic identifiers; and

wherein said step of storing an identifier of the second topic set as a negative subscription is only performed when the second topic set comprises a subset of the identified topic set of a positive subscription.

14. The computer program product of claim 13 further comprising a program instruction for causing performance of the step of, in response to a request from a subscriber to subscribe to a topic set, determining if any stored topic identifier of a current positive subscription is included in a newly subscribed topic set and, if so, replacing the stored topic identifier with the topic set identifier.

15. The computer program product of claim 14 further comprising a program instruction for causing performance of the step of, in response to a request from a subscriber to subscribe to a topic or topic set, adding an identifier of the topic or topic set to the stored positive subscriptions if the topic or topic set is not already identified in a stored positive subscription, or if the requested topic or topic set overlaps a topic or topic set of a stored negative subscription.