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dap commit: Adding Web Intents Addendum for Local Services as it once again by some reason has been disappeared from the directory!

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Date: Sun, 02 Sep 2012 09:13:39 +0000
Message-Id: <E1T86FP-0008AX-9Z@mcbain.w3.org>
To: public-dap-commits@w3.org
changeset:   214:267ff8e9346c
tag:         tip
user:        Claes Nilsson <claes1.nilsson@sonymobile.com>
date:        Sun Sep 02 11:11:35 2012 +0200
files:       wi-addendum-local-services/Example1_registration_page/Slide1.png wi-addendum-local-services/Example_device_and_service_description_pages/Slide1.png wi-addendum-local-services/Example_device_and_service_description_pages/Slide2.png wi-addendum-local-services/Example_scenario_1/Slide1.png wi-addendum-local-services/Example_scenario_1/Slide2.png wi-addendum-local-services/Example_scenario_1/Slide3.png wi-addendum-local-services/Example_scenario_2/Slide1.png wi-addendum-local-services/Example_scenario_2/Slide2.png wi-addendum-local-services/Example_scenario_2/Slide3.png wi-addendum-local-services/Example_scenario_2/Slide4.png wi-addendum-local-services/Overview.html
description:
Adding Web Intents Addendum for Local Services as it once again by some reason has been disappeared from the directory!


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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wi-addendum-local-services/Overview.html	Sun Sep 02 11:11:35 2012 +0200
@@ -0,0 +1,736 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Web Intents Addendum - Local Services</title>
+    <meta http-equiv='Content-Type' content='text/html;charset=utf-8'/>
+    <!-- 
+      === NOTA BENE ===
+      For the three scripts below, if your spec resides on dev.w3 you can check them
+      out in the same tree and use relative links so that they'll work offline,
+     -->
+    <script src='http://www.w3.org/Tools/respec/respec-w3c-common' class='remove'></script>
+    <script class='remove'>
+      var respecConfig = {
+          // specification status (e.g. WD, LCWD, NOTE, etc.). If in doubt use ED.
+          specStatus:           "ED",
+          
+          // the specification's short name, as in http://www.w3.org/TR/short-name/
+          shortName:            "Web Intents-LD addendum",
+
+          // if your specification has a subtitle that goes below the main
+          // formal title, define it here
+          // subtitle   :  "an excellent document",
+
+          // if you wish the publication date to be other than today, set this
+          // publishDate:  "2009-08-06",
+
+          // if the specification's copyright date is a range of years, specify
+          // the start date here:
+          // copyrightStart: "2005"
+
+          // if there is a previously published draft, uncomment this and set its YYYY-MM-DD date
+          // and its maturity status
+          // previousPublishDate:  "1977-03-15",
+          // previousMaturity:  "WD",
+
+          // if there a publicly available Editor's Draft, this is the link
+          // edDraftURI:           "http://dev.w3.org/2009/dap/ReSpec.js/documentation.html",
+
+          // if this is a LCWD, uncomment and set the end of its review period
+          // lcEnd: "2009-08-05",
+
+          // if you want to have extra CSS, append them to this list
+          // it is recommended that the respec.css stylesheet be kept
+          extraCSS:             ["http://dev.w3.org/2009/dap/ReSpec.js/css/respec.css"],
+
+          // editors, add as many as you like
+          // only "name" is required
+          editors:  [
+              { name: "Claes Nilsson",
+                company: "Sony Mobile", companyURL: "http://www.sonymobile.com/se/" },
+              { name: "Norifumi Kikkawa",
+                company: "Sony Corporation", companyURL: "http://www.sony.net/"},
+          ],
+
+          // authors, add as many as you like. 
+          // This is optional, uncomment if you have authors as well as editors.
+          // only "name" is required. Same format as editors.
+
+          //authors:  [
+          //    { name: "Your Name", url: "http://example.org/",
+          //      company: "Your Company", companyURL: "http://example.com/" },
+          //],
+          
+          //
+          edDraftURI: "http://w3c-test.org/dap/wi-addendum-local-services/",
+          
+          // name of the WG
+          wg:           "DAP/Web Apps Web Intents task force",
+          
+          // URI of the public WG page
+          wgURI:        "http://www.w3.org/2009/dap/",
+          
+          // name (without the @w3c.org) of the public mailing to which comments are due
+          wgPublicList: "public-web-intents",
+          
+          // URI of the patent status for this WG, for Rec-track documents
+          // !!!! IMPORTANT !!!!
+          // This is important for Rec-track documents, do not copy a patent URI from a random
+          // document unless you know what you're doing. If in doubt ask your friendly neighbourhood
+          // Team Contact.
+          wgPatentURI:  "",
+      };
+    </script>
+  </head>
+  <body>
+    <section id='abstract'>
+      This specification is an addendum to Web Intents, [[!WEBINTENTS]], that defines how Web Intents enabled User Agents can discover and communicate 
+      with local Web Intents Services.
+    </section>
+    
+    <section class='informative'>
+      <h2>Introduction</h2>
+      <p>
+        Web Intents,[[!WEBINTENTS]], is a service discovery and light-weight RPC mechanism for web applications. The concept enables rich integration between web applications. 
+        A typical Web Intents scenario is:
+      </p>
+      <ol>
+         <li>Web Intents Services register their intention to handle an action for the user </li>
+         <li>A web application requests to start an action (share, edit, pick, view, ...)</li>
+         <li>The user selects which service to handle the action</li>
+      </ol>
+      <p>
+        A Web Intents Service is represented by a web page that declaratively marks itself as providing handling functionality for particular intents. Users register Web Intents Services 
+        by visiting web pages that contain registration markup.
+        However, the strength of Web Intents is the ability to provide web applications with access to Services residing not only in the cloud but also in local environments.
+      </p>
+      <p>
+        This specification defines optional extensions to Web Intents enabled User Agents to discover and dynamically register local Web Intents 
+        Services. Note that all details of the specific low level protocols used to discover and communicate with the local services are hidden to
+        the Client Web Applications.          
+      </p>   
+      <p>
+        The following code illustrates how a web application containing links to videos, can initiate video playback by creating and invoking a "video intent" as defined in [[!WEBINTENTS]].
+        This code is the same irrespective of whether the Service executing the intent action is a cloud based Service or a local Service.
+      </p>
+      <pre class="example sh_javascript_dom">
+      
+        // Create a new intent
+var intent = new Intent( "http://webintents.org/view","video/mp4",{ "src":videoCanvas.src, "img": videoCanvas.poster});
+					
+// Start intents picker 
+navigator.startActivity(intent,
+  // On Result
+  function(intentData) {console.log("player.html: On Result" + intentData);}, 
+  // On Failure
+  function(intentData) {console.log("player.html: On Failure" + intentData);});
+      </pre>
+      <p>
+        The example below briefly describes the steps taken when a Service on a local network, e.g. UPnP or mDNS, device is discovered and selected by 
+        the user.
+      </p>      
+      
+      <ol>
+         <li>Triggered by navigator.startActivity the User Agent will start local network discovery of Web Intents Services.</li>
+         <li>Replies from Web Intents enabled devices contain a URL to a Web Intents document, containing Web Intents Service registration 
+             markup, in the device. </li>
+         <li>The Web Intents documents are retrieved by the User Agent and the dynamically registered Services are visible in the Web Intents Service picker. </li>
+         <li>User selects Service.</li>
+         <li>User Agent retrieves the Service page from the the Web Intents local network device and invokes it. </li>
+         <li>The Service page handles the intent. </li>  
+         <li>When handling the intent is finished, the Service page issues window.intent.postResult and closes itself. </li>               
+      </ol>
+      
+    </section>
+    
+    <section id="conformance">     
+      <p>        
+        This specification defines conformance criteria that apply to:
+        <ul>
+          <li><dfn>UPnP enabled User Agent</dfn>: A <a>UPnP enabled User Agent</a> MUST support Web Intents [[!WEBINTENTS]] and the conformance criteria 
+          stated in this specification. </li>
+          <li><dfn>Web Intents enabled UPnP device</dfn>: A <a>Web Intents enabled UPnP device</a> MUST support [[!UPNP-DEVICEARCH]] and the conformance criteria 
+          stated in this specification. </li>
+          <li><dfn>mDNS enabled User Agent</dfn>: An <a>mDNS enabled User Agent</a> MUST support Web Intents [[!WEBINTENTS]] and the conformance criteria 
+          stated in this specification. </li>
+          <li><dfn>Web Intents enabled mDNS device</dfn>: A <a>Web Intents enabled mDNS device</a> MUST support [[!DNS-SD]], [[!MDNS]] and the conformance criteria 
+          stated in this specification. </li>
+        </ul>
+      </p>
+      <p>
+        Implementations that use ECMAScript to implement the APIs defined in
+        this specification must implement them in a manner consistent with the
+        ECMAScript Bindings defined in the Web IDL specification [[!WEBIDL]],
+        as this specification uses that specification and terminology.
+      </p>
+      <section>
+        <h2>Dependencies</h2>
+        <p>
+          This specification relies on the following specifications:
+          
+          <dl>
+            <dt>Web Intents</dt>
+            <dd>This addendum specification is dependent on and defines optional extensions to the basic Web Intents specification, [[!WEBINTENTS]]. </dd>
+            <dt>UPnP Device Architecture 1.0</dt>
+            <dd>This addendum specification is dependent on and defines vendor specific extensions to the UPnP Device Architecture 1.0 specification, [[!UPNP-DEVICEARCH]]. </dd>
+            <dt>IANA Service Name and Transport Protocol Port Number Registry</dt>
+            <dd>This addendum specification adds new entry on it, [[!IANA-SRVPORT-REG]]. </dd>
+            <dt>DNS-SD</dt>
+            <dd>This addendum specification is dependent on it, [[!DNS-SD]]. </dd>
+            <dt>mDNS</dt>
+            <dd>This addendum specification is dependent on it, [[!MDNS]]. </dd>
+         </dl>
+          
+        </p>      
+      </section>
+    </section>
+    
+    <section>
+      <h2>Terminology</h2>
+      <p>
+        Web Intents related terms are used according to section "Terminology" in [[!WEBINTENTS]].
+      </p>
+     
+      <section> 
+        <h3>UPnP related terms</h3>
+        <p>
+          UPnP related terms are used according to [[!UPNP-DEVICEARCH]]. 
+        </p>
+        <p>
+          The <a>UPnP enabled User Agent</a> has the role of a <dfn id="dfn-registration">control point</dfn>  according to UPnP terminology. 
+        </p>     
+        <p>
+          The <a>Web Intents enabled UPnP device</a> discovered by the <a>UPnP enabled User Agent</a> has the roles of <dfn id="dfn-registration">device</dfn> according to UPnP terminology. 
+        </p>        
+      </section>
+      
+      <section> 
+        <h3>mDNS related terms</h3>
+        <p>
+          The <a>mDNS enabled User Agent</a> has the role of a <dfn id="dfn-registration">DNS client</dfn> with capability of [[!DNS-SD]]. 
+        </p>
+        <p>
+          The <a>Web Intents enabled mDNS device</a> discovered by the <a>mDNS enabled User Agent</a> has the roles of <dfn id="dfn-registration">service</dfn> according to [[!MDNS]] and [[!DNS-SD]]. 
+        </p>        
+      </section>     
+      
+
+    </section>
+    
+    <section>
+    
+      <h2>UPnP adaptation</h2> 
+      
+      <section>   
+      
+        <h3><a>Web Intents enabled UPnP device</a></h3> 
+        
+        <p>
+          The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support this section.
+        </p>
+        
+        <section>    
+        
+          <h4>UPnP Web Intents serviceType</h4>
+          
+          <p>
+            The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support one UPnP service which serviceType is the <code>urn:schemas-webintents-org:service:WebIntents:1</code> 
+            as a vendor specific serviceType according to [[!UPNP-DEVICEARCH]]. It is vendor dependent how the <a>Web Intents enabled UPnP device</a> implements the serviceType, 
+            i.e. a device description of any deviceType could include this serviceType.
+          </p>  
+          
+          <p>          
+            The Web Intents serviceType <em class="rfc2119" title="must">must</em> have a dummy state variable, <code>X_State</code> of <code>boolean</code> data type to comform to [[!UPNP-DEVICEARCH]]
+            which requires one or more state variables in a serviceType. The <code>X_State</code> state variable is not used with a value and is never evented. 
+          </p>  
+          <p>
+            The Web Intents  serviceType has no standard action.          
+          </p>          
+
+          <p>
+            See below for the UPnP Service description document of the Web Intents serviceType.
+          </p>           
+          
+          <p align="left"><img src="Example_device_and_service_description_pages/Slide2.png" alt="Service description page" width="600" height="600" ><br>
+           (<a href="Example_device_and_service_description_pages/Slide2.png">View as PNG</a>)
+          </p>   
+             
+        
+        </section>   
+        
+        <section>    
+        
+          <h4>Web Intents specific SSDP headers</h4>           
+
+          <p>
+            The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support SSDP discovery process based on standard UPnP Discovery extended with 2 additional 
+            SSDP headers for M-SEARCH response and NOTIFY when ST/NT headers are:<code>urn:schemas-webintents-org:service:WebIntents:1</code>
+          </p>
+        
+          <ul>
+            <li>
+              <code>location.webintents.org</code>: <em class="rfc2119" title="required">required</em>. States the location to the Web Intents document in the <a>Web Intents enabled UPnP device</a>. 
+              If the value of this header is a relative URL the base URL is the base URL of the <code>LOCATION</code> header.  
+            </li>
+            <li>
+              <code>action.webintents.org</code>: <em class="rfc2119" title="optional">optional</em>. If supported, states the Web Intents 
+              <code>action</code> of the supported Web Intents Services and <em class="rfc2119" title="must">must</em>
+              match the <code>action</code> attributes of the Service registration markup in the Web Intents document. To support more than 
+              one Web Intents <code>action</code> the action strings <em class="rfc2119" title="must">must</em> be separated with 
+              comma. Commas included in action strings <em class="rfc2119" title="must">must</em> be percent-encoded as 
+              defined in [[!RFC3986]], section-2.1.
+              <br />  <br />
+              This header allows the <a>UPnP enabled User Agent</a> to filter received SSDP messages so that the <a>UPnP enabled User Agent</a> only has to 
+              retrieve Web Intents documents for matching Web Intents Actions.        
+            </li>
+          </ul>         
+
+        </section>   
+        
+        <section>    
+        
+          <h4>Web Intents document</h4>   
+
+          <p>
+            The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> host Web Intents documents for the Web Intents Services the <a>Web Intents enabled UPnP device</a> supports. 
+            Web Intents documents are html pages that contain Web Intents Service registration markup according to the rules for Web Intents Service registration defined 
+            by [[!WEBINTENTS]]. They may also contain Service handler code for Services registered within the same document. 
+          </p>              
+        
+        </section>   
+        
+        <section>    
+        
+          <h4>Web Intents Service pages</h4>    
+          
+          <p>
+            The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> host a Web Intents Service page for each Service that is 
+            referred in Web Intents documents through <code>href</code> attributes in the registration markup. 
+          </p>
+          <p>
+            Service pages contain Service handler code and fulfills the rules for Web Intents Services as defined by [[!WEBINTENTS]]. 
+          </p>   
+        
+        </section>          
+        
+      </section>   
+      
+      <section>
+      
+        <h3><a>UPnP enabled User Agent</a></h3> 
+        
+        <p>
+          The <a>UPnP enabled User Agent</a> <em class="rfc2119" title="must">must</em> support discovery of <a>Web Intents enabled UPnP device<a>s through SSDP Discovery or through Advertisement 
+          or through both methods according to [[!UPNP-DEVICEARCH]] and according to the Web Intents serviceType and Web Intents specific SSDP headers 
+          defined in this specification, section 4.1. 
+        </p>
+  
+        <p>
+          The sections below describe typical steps using these methods.
+        </p>
+       
+          <section class='informative'>
+            <h4>Dynamic Service registration based on M-SEARCH</h4>
+
+            <p>
+              The section describes the discovery process based on standard UPnP M-SEARCH multicast request.
+            </p>
+            
+            <p>
+              When the navigator.startActivity method [[!WEBINTENTS]] is called, the <a>UPnP enabled User Agent</a> runs the following steps:
+            </p>
+              
+            <ol class="rule">          
+              <li>
+                 Send a multicast request with the method M-SEARCH in the format specified by [[!UPNP-DEVICEARCH]].
+                 <br />
+                 The <code>ST</code> header is set to: <code>urn:schemas-webintents-org:service:WebIntents:1</code>
+              </li>
+              <br />
+              <li>
+                 For each matching M-SEARCH response, i.e. the response ST header is <code>urn:schemas-webintents-org:service:WebIntents:1</code> and the <code>action.webintents.org</code> 
+                 header, if present, matches the Action of the invoked intent, 
+                 the <a>UPnP enabled User Agent</a> attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled UPnP device</a>.              
+                 The value of the <code>location.webintents.org</code> header is the location for the Web Intents document. 
+                 If this value is a relative URL the <a>UPnP enabled User Agent</a> uses the base URL of the <code>LOCATION</code> header as base URL for the location of the 
+                 Web Intents document.  
+                 <br />  <br />
+                 If the <a>UPnP enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received M-SEARCH response.
+                 <br />  <br />
+                 If the <code>action.webintents.org</code> header is present and does not match the <code>action</code> attributes of the Services registered in the retrieved Web Intents 
+                 document the <a>UPnP enabled User Agent</a> silently disregards the the received M-SEARCH response.
+              </li>
+              <br />         
+              <li>
+                 It is expected that the Web Intents document contains registration markup and the <a>UPnP enabled User Agent</a> interprets this
+                 registration markup according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.           
+              </li>
+              <br />          
+              <li>
+                 The <a>UPnP enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection 
+                 by the user, typically by making them visible and selectable in a Web Intents Service picker.                          
+              </li>
+              <br />          
+              <li>
+                 Based on user selection of a dynamically registered Service the <a>UPnP enabled User Agent</a> loads the 
+                 Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for 
+                 loading Service pages defined in [[!WEBINTENTS]].                        
+              </li>
+      
+            </ol> 
+     
+          </section>
+          
+          <section class='informative'>
+            <h4>Dynamic Service registration based on NOTIFY</h4>
+            <p>
+              This section describes the discovery process based on standard UPnP Advertisement with NOTIFY message.            
+            </p> 
+           
+            <p>
+             The <a>UPnP enabled User Agent</a> <em class="rfc2119" title="may">may</em> continuously listen to and act on advertisments according to the following steps:
+            </p>   
+            <ol class="rule">   
+          
+              <li>
+                The <a>UPnP enabled User Agent</a> maintains a list of announced UPnP services based on received SSDP NOTIFY messages
+                with <code>NT</code> header equal to <code>urn:schemas-webintents-org:service:WebIntents:1</code>.
+              </li>
+              <br /> 
+              <li>
+                When the navigator.startActivity method [[!WEBINTENTS]] is called the <a>UPnP enabled User Agent</a> checks the list
+                of of announced services and attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled UPnP device</a> in the following cases:                
+                <ul>
+                  <li>
+                    The received NOTIFY message contains an <code>action.webintents.org</code> header and this header matches the Action of the invoked intent.
+                  </li>
+                  <li>
+                    The received NOTIFY message does not contain an <code>action.webintents.org</code> header.
+                  </li>                
+                </ul>
+                <br />     
+                The location of the Web Intents document is the value of the <code>location.webintents.org</code> header. If this value is a relative URL the
+                base URL is the base URL of the <code>LOCATION</code> header.  
+                <br />  <br />
+                If the <a>UPnP enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received NOTIFY message.
+                <br />  <br />
+                If the <code>action.webintents.org</code> header does not match the <code>action</code> attribute in the retrieved Web Intents document 
+                the <a>UPnP enabled User Agent</a> silently disregards the received NOTIFY message.
+              </li>
+              <br />         
+              <li>
+                 It is expected that the Web Intents document contains registration markup and the <a>UPnP enabled User Agent</a> interprets the
+                 Web Intents document according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.                         
+              </li>
+              <br />          
+              <li>
+                 The <a>UPnP enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection 
+                 by the user, typically by making them visible and selectable in a Web Intents Service picker.                          
+              </li>
+              <br />          
+              <li>
+                 Based on user selection of a dynamically registered Service the <a>UPnP enabled User Agent</a> loads the 
+                 Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for 
+                 loading Service pages defined in [[!WEBINTENTS]].                          
+              </li>
+            </ol> 
+             
+            <p class="note">
+              Power consumption in battery powered devices should be considered. If power consumption is severe continuously listening to SSDP advertisement in the background 
+              should not be used..          
+            </p> 
+          
+          </section>  
+          
+          <section class='informative'>  
+            <h4>Support for Web Intents and UPnP</h4>
+            <p>
+              In addition to the normative statements defined in this specification a <a>UPnP enabled User Agent</a> that complies to this specification 
+              supports Web Intents according to [[!WEBINTENTS]] and UPnP Discovery, Description and Control according to [[!UPNP-DEVICEARCH]]. 
+              However, it is implementation dependent whether this is supported natively in the User Agent or supported through some external component, 
+              e.g. an in-device web server. 
+            </p>         
+          </section>           
+          
+          <section class='informative'>
+      
+            <h4>Service availability management</h4>
+
+            <p>
+             The <a>UPnP enabled User Agent</a> should manage the availability of UPnP services. For example detect when contact with a <a>Web Intents enabled UPnP device</a> is lost through standard
+             UPnP life cycle management and remove a previously discovered and registered Service from the Service picker. However, for battery powered devices
+             power consumption should be considered and long lasting "keep alive" sessions" should be avoided.           
+            </p>        
+        
+          </section>
+
+      </section>        
+      
+   
+      
+    </section>   
+    
+    <section>
+    
+      <h2>mDNS (DNS-SD) adaptation</h2> 
+      
+      <p>
+        This section describes how the User Agent handles Web Intents Services provided by local devices supporting mDNS and DNS-SD.          
+      </p>
+
+      <section>   
+      
+        <h3>Web Intents enabled mDNS device</h3> 
+        
+        <p>
+          The <a>Web Intents enabled mDNS device</a> <em class="rfc2119" title="must">must</em> support this section.
+        </p>
+        
+        <section>    
+        
+          <h4>Web Intents service type for DNS-SD</h4>     
+          
+          <p>
+            The <a>Web Intents enabled mDNS device</a> <em class="rfc2119" title="must">must</em> support [[!DNS-SD]] with a SRV record of the <code>webintents</code> service type. 
+          </p>  
+          
+            <p class="note">
+              A service type <code>webintents</code> should be registered in [[!IANA-SRVPORT-REG]].
+            </p>
+
+          <p>          
+            The TXT record for the <code>webintents</code> service must have following parameters:           
+          </p>          
+          <ul>
+            <li>
+              <code>location</code>: <em class="rfc2119" title="required">required</em>. States the location to the Web Intents document in the <a class="internalDFN" href="#dfn-web-intents-enabled-mdns-device">Web Intents enabled mDNS device</a>. 
+              The value of this header is path to be concatenated with a host of the <a class="internalDFN" href="#dfn-web-intents-enabled-mdns-device">Web Intents enabled mDNS device</a> to determine the location. The definition of the Web Intents document is the same as for UPnP.
+            </li>
+            <li>
+              <code>action</code>: <em class="rfc2119" title="optional">optional</em>. If supported, states the Web Intents 
+              <code>action</code> of the supported Web Intents Services and <em class="rfc2119" title="must">must</em>
+              match the <code>action</code> attributes of the Service registration markup in the Web Intents document. To support more than 
+              one Web Intents <code>action</code> the action strings <em class="rfc2119" title="must">must</em> be separated with 
+              comma. Commas included in action strings <em class="rfc2119" title="must">must</em> be percent-encoded as 
+              defined in [[!RFC3986]], section-2.1.
+              <br>  <br>
+              This allows the <a>mDNS enabled User Agent</a> to filter received mDNS messages so that the <a>mDNS enabled User Agent</a> only has to 
+              retrieve Web Intents documents for matching Web Intents Actions.        
+            </li>
+          </ul>         
+
+        </section>   
+        
+      </section>   
+      <section>    
+        <h3>mDNS enabled User Agent</h3> 
+
+        <p>
+          The <a>mDNS enabled User Agent</a> <em class="rfc2119" title="must">must</em> support discovery of <a>Web Intents enabled mDNS device<a>s through mDNS and DNS-SD 
+          according to [[!MDNS]], [[!DNS-SD]] and according to the Web Intents specific DNS records defined in this specification, section 5.1. 
+        </p>
+        
+        <section class='informative'>
+          <h4>Dynamic Service registration</h4>   
+          <p>
+            When the navigator.startActivity method [[!WEBINTENTS]] is called, the <a>mDNS enabled User Agent</a> typically runs the following steps:
+          </p>
+            
+          <ol class="rule">          
+            <li>
+               Send a multicast PTR query of the <code>_webintents._tcp.local</code> in the format specified by [[!MDNS]] and [[!DNS-SD]].
+               <br />
+            </li>
+            <br />
+            <li>
+               For each response, send a unicast TXT query of the webintents service instance in the PTR answer.
+               <br />
+               <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches a TXT answer with the previous answer.
+            </li>
+            <br />
+            <li>
+               For each matching response, i.e. the response TXT record does not have an action parameter or does have an <code>action</code> parameter matching the Action of the invoked intent,
+               send a unicast request with a SRV query of the webintens service instance.
+               <br />
+               <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches a SRV answer with the previous answer.
+            </li>
+            <br />
+            <li>
+               For each response, send a unicast A and/or AAAA query of the host name in the SRV answer.
+               <br />
+               <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches an A and/or AAAA answer with the previous answer.
+            </li>
+            <br />
+            <li>
+               The <a>mDNS enabled User Agent</a> attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled mDNS device</a>.
+               The destination URL consists of an IP address in the A or AAAA answer, a port number in the SRV record and an absolute path in the <code>location</code> parameter of the TXT record.  
+               <br />  <br />
+               If the <a>mDNS enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received response.
+               <br />  <br />
+               If the <code>action</code> parameter is present and does not match the <code>action</code> attributes of the Services registered in the retrieved Web Intents 
+               document the <a>mDNS enabled User Agent</a> silently disregards the the received response.
+               <br />  <br />
+               Note that following steps are identical to those of UPnP described in 4.2.
+            </li>
+            <br />          
+            <li>
+               It is expected that the Web Intents document contains registration markup and the <a>mDNS enabled User Agent</a> interprets this
+               registration markup according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.           
+            </li>
+            <br />          
+            <li>
+               The <a>mDNS enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection 
+               by the user, typically by making them visible and selectable in a Web Intents Service picker.                          
+            </li>
+            <br />          
+            <li>
+               Based on user selection of a dynamically registered Service the <a>mDNS enabled User Agent</a> loads the 
+               Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for 
+               loading Service pages defined in [[!WEBINTENTS]].                        
+            </li>
+    
+          </ol> 
+                 
+        </section>          
+
+      </section>    
+      <section class="informative">
+        <h3>Sample Records</h3> 
+        
+        <p>
+          See below for the example records for Web Intents. An <a>mDNS enabled User Agent</a> looking for devices supporting http://webintents.org/view Web Intents can understand that 
+          it is possible to get a Web Intents document for "LivingRoomTV" at http://192.168.1.47:3619/webintents.html.
+        </p>
+
+        <ul>
+          <li>
+            <code>_webintents._tcp.local. 120 IN PTR LivingRoomTV._webintents._tcp.local.</code>: A LivingRoomTV instance serves webintents service.
+          </li>
+          <li>
+            <code>LivingRoomTV._webintents._tcp.local. 120 IN SRV 0 0 3619 TV40EX-W2000.local.</code>: A host "TV40EX-W2000" in the link local network offers the LivingRoomTV webintents service instance in its port 3619.
+          </li>
+          <li>
+            <code>LivingRoomTV._webintents._tcp.local. 120 IN TXT location=/webintents.html action=http://webintents.org/view</code>: It offers http://webintents.org/view type of Web Intents. The absolete path for its Web Intents document is "/webintents.html". Note that the actual binary format of the TXT record value is concatinating key-value pairs each of which is a single byte length followed by 0-255 length key=value character string as defined in [DNS-SD].
+          </li>
+          <li>
+            <code>TV40EX-W2000 120 IN A 192.168.1.47</code>: A host "TV40EX-W2000" is on 192.168.1.47.
+          </li>
+        </ul>
+
+      </section>   
+                 
+    </section>         
+    
+        
+    <section class='informative'>
+      <h2>APIs / protocols Client - Service </h2>
+      <p>
+        The APIs / protocols for interaction between Client and Service pages are not defined by this specification. It is assumed that Web Intents 
+        based APIs and protocols will be standardized by W3C and that these will be applicable for Client and Service applications running on User Agents that
+        comply to this specification. Different use cases will require different ways of interaction patterns between Client and Service. 
+      </p>
+      
+      <p>
+        Examples:
+      </p>  
+      <ul>
+        <li>
+          A Client application invoking a "View" intent provides, as intent payload data, a link to a video to be displayed at the remote <a>Web Intents enabled UPnP device</a>.
+          The Service application takes full control of the video playback by providing control buttons and sends UPnP commands to the remote device.
+          So in this case there the simple "API" just gives the link to the video to play. 
+        </li>
+        <li>
+          Some use cases require a longer lasting relation between the Client and Service applications. By using the MessagePort[] attribute of the intent object 
+          a message channel can be established between the Client and Service page. This message channel can be used to run Service specific protocols, 
+          for example a protocol that allows the Client application to send simple video playback control commands to a Service application. 
+        </li>
+      </ul>          
+      
+    </section>  
+           
+    <section class='informative appendix'>
+    <h2>Examples and scenarios</h2>
+      <section>
+        <h3>View and control video on remote device through Service page control buttons</h3>
+        <p>
+          The following scenario describes how a Client page uses Web Intents to discover a remote video view service. The Service page 
+          contains the UI for controlling the video playback.
+        </p>
+        
+        <p align="left"><img src="Example_scenario_1/Slide1.png" alt="Example scenario 1/Slide1" width="700" height="700" ><br>
+         (<a href="Example_scenario_1/Slide1.png">View as PNG</a>)
+        </p>      
+        
+        <p align="left"><img src="Example_scenario_1/Slide2.png" alt="Example scenario 1/Slide2" width="700" height="700" ><br>
+         (<a href="Example_scenario_1/Slide2.png">View as PNG</a>)
+        </p> 
+        
+        <p align="left"><img src="Example_scenario_1/Slide3.png" alt="Example scenario 1/Slide3" width="700" height="700" ><br>
+         (<a href="Example_scenario_1/Slide3.png">View as PNG</a>)
+        </p>                 
+      </section>  
+      
+      <section>
+        <h3>View and control video on remote device through Client page control buttons</h3>
+        <p>
+          The following scenario describes how a Client page uses Web Intents to discover a remote video view service. The UI stays in the Client page, 
+          which contains the UI controls for the video playback. This means that there is a need for continuous communication between the Client page and the Service page,
+          which is "hidden", i.e. it has no UI. The Client page creates a messaging channel and sends the messaging channel port to the Service page trhrough the intent invocation.
+          A high level "TV control" protocol, supporting commands such as "play", "pause" and "stop, runs on top of the messaging channel. 
+        </p>
+        <p>
+          In this example the assumption is that he Client invokes an intent to discover a Service that supports a specified protocol running on top of the message channel So the 
+          "discover" intent Action is used and Type is set to the specific protocol used to communicate with the Service.
+        </p>
+        
+        <p class="issue">
+          This scenario assumes the possibility to have hidden/background Service pages or Service pages that are visible inline the Client page.
+          Currently [[!WEBINTENTS]] does not allow this but W3C DAP Action http://www.w3.org/2009/dap/track/actions/519 should add a proposal for a hidden disposition. 
+        </p>   
+        
+        <p align="left"><img src="Example_scenario_2/Slide1.png" alt="Example scenario 2/Slide1" width="700" height="700" ><br>
+         (<a href="Example_scenario_2/Slide1.png">View as PNG</a>)
+        </p>      
+        
+        <p align="left"><img src="Example_scenario_2/Slide2.png" alt="Example scenario 2/Slide2" width="700" height="700" ><br>
+         (<a href="Example_scenario_2/Slide2.png">View as PNG</a>)
+        </p> 
+        
+        <p align="left"><img src="Example_scenario_2/Slide3.png" alt="Example scenario 2/Slide3" width="700" height="700" ><br>
+         (<a href="Example_scenario_2/Slide3.png">View as PNG</a>)
+        </p>    
+        
+        <p align="left"><img src="Example_scenario_2/Slide4.png" alt="Example scenario 2/Slide4" width="700" height="700" ><br>
+         (<a href="Example_scenario_2/Slide4.png">View as PNG</a>)
+        </p>                       
+      </section>  
+            
+      
+    
+      <section>
+        <h3>Example of Web Intents document</h3>
+      
+        <p align="left"><img src="Example1_registration_page/Slide1.png" alt="Example1 registration page" width="280" height="280" ><br>
+         (<a href="Example1_registration_page/Slide1.png">View as PNG</a>)
+        </p>      
+      </section>      
+    
+      <section>
+        <h3>Example of UPnP Device description document</h3>
+        <p align="left"><img src="Example_device_and_service_description_pages/Slide1.png" alt="Example device and service description pages/Slide1" width="600" height="600" ><br>
+         (<a href="Example_device_and_service_description_pages/Slide1.png">View as PNG</a>)
+        </p>   
+      </section>
+            
+    </section>           
+    
+    <section class='appendix'>
+      <h3>Acknowledgements</h3>
+        <p>         
+          Many thanks to Sony colleagues Anders Isberg, Naoyuki Sato, Tatsuya Igarashi, Anders Edenbrandt and Björn Ekberg for all support.
+          <br />  <br />
+          Many thanks to Robin Berjon for making our lives so much easier with his cool specification editing tool.
+        </p>
+    </section>
+  </body>
+</html>
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