1 <?xml version="1.0" encoding="utf-8"?>

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-8255A186-C1AC-44DA-844C-1FEA029C73BC" xml:lang="en"><title>Publish

    13 and Subscribe</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p><i>Publish and Subscribe</i> has replaced System Agent and the usage

    15 of temporary Shared Data keys.</p>

    16 <p>Publish and Subscribe allows the setting, retrieving and monitoring

    17 of system-wide variables and provides a new inter process communication (IPC)

    18 mechanism for peer to peer communication between threads. Threads may have

    19 the role of the publisher or of the subscriber, while any thread can define

    20 the property to be published. The process that defines a property can specify

    21 access rights for both reading and writing. Rights can be defined in terms

    22 of either requiring a particular <xref href="GUID-6971B0A2-F79B-4E05-8AF3-BB1FC1932A22.dita">capability</xref>,

    23 by a process <xref href="GUID-3B6E25F7-C1A8-461F-97F7-421DB559BC98.dita#GUID-3B6E25F7-C1A8-461F-97F7-421DB559BC98/GUID-EEC50FC0-46D5-4ED7-AD95-67430D5EC652">Secure

    24 Identifier</xref>, or by a process <xref href="GUID-3B6E25F7-C1A8-461F-97F7-421DB559BC98.dita#GUID-3B6E25F7-C1A8-461F-97F7-421DB559BC98/GUID-EEC50FC0-46D5-4ED7-AD95-67430D5EC654">VID</xref>. </p>

    25 <p>Publish and Subscribe should be considered under any of the following

    26 conditions:</p>

    27 <ul>

    28 <li><p>An event should be sent simultaneously to multiple places

    29 over the system.</p></li>

    30 <li><p>Only the last value of the property is significant, not the

    31 intermediate values.</p></li>

    32 <li><p>The source of the value is not significant. The value may

    33 have been set by any publisher with proper rights.</p></li>

    34 </ul>

    35 <p>For more information about the use of Publish and Subscribe, see <xref href="GUID-FE910347-7CC1-5241-B443-88AD3F5A96EF.dita">Using Publish and Subscribe</xref>.</p>

    36 </conbody></concept>