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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-5580195F-3DE7-55FA-B2C1-91A950A39C6E" xml:lang="en"><title>Nodes |
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13 in Symbian Platform</title><shortdesc>This topic describes the basic concept of a <i>Node</i> in Symbian |
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14 platform. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 |
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16 <p>The Communications Framework is modular and can adapt to changes in the |
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17 networks that are available. The Communications Framework can also adapt to |
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18 changes in technology. The modular design is described as a <i>Distributed |
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19 Object Model</i>. Nodes are the components of a Distributed Object Model. </p> |
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20 <p>A Distributed Object Model describes a system of entities or <i>Nodes</i> that |
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21 can exist in different run contexts. The Nodes can exchange asynchronous messages. |
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22 In Symbian platform, the concept of different run contexts refers to separate |
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23 threads and separate processes. The scope of a Node is limited to a device. |
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24 A Node cannot exist on a separate device. </p> |
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25 <p>Symbian platform provides the Distributed Object Model framework that the |
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26 Communications Architecture uses. The Distributed Object Model framework is |
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27 a general purpose tool that other software entities can also use. </p> |
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28 <p>A Node is an object that has an interface and an address. A Node uses messages |
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29 to communicate with other Nodes. Some types of Node can use direct function |
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30 calls to communicate if speed is important. Symbian platform defines the interface |
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31 to a Node as the sequence of messages that the Node knows and to which the |
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32 Node responds. </p> |
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33 <p>A Node is an instance of a class derived from <xref href="GUID-3462501E-FDE1-3F3C-B26D-7FF3C826311F.dita"><apiname>ANodeBase</apiname></xref>. </p> |
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34 <p>A parent Node is responsible for the destruction of its child Nodes. A |
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35 parent Node can pass a reference to a child Node to other Nodes and implements |
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36 the concept of containment. </p> |
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37 <p>Nodes have <i>Roles</i>. A Role : </p> |
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38 <ul> |
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39 <li id="GUID-FCAA95EC-73CE-55D6-958F-4489069915D9"><p>identifies a service |
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40 that the Node provides </p> </li> |
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41 <li id="GUID-D9A10365-54BC-5F28-A081-FBB9963FCA38"><p>describes the series |
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42 of messages that a Node sends and receives as part of a service </p> </li> |
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43 </ul> |
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44 <p>A Node can have more than one role. Examples of roles are as follows: </p> |
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45 <ul> |
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46 <li id="GUID-76207994-4326-5CB1-BE14-F20037A9B0BE"><p>a Node can accept requests |
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47 to connect to another Node. </p> </li> |
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48 <li id="GUID-3F4B59F6-12DD-5381-ACE9-DD021F41BF66"><p>a Node can own other |
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49 Nodes. This is the concept of the <i>parent</i> Node. </p> </li> |
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50 <li id="GUID-1B92A012-72B4-5DAC-9F15-D7FB802E2625"><p>A Node can be owned |
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51 by another Node. This is the concept of the <i>child</i> Node. </p> </li> |
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52 </ul> |
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53 </conbody></concept> |