Device Description Structures

1 Introduction

The mobile handset market is innovative and dynamic but at the same time fragmented. The result is that there are thousands of different devices made by multiple manufacturers. Nonetheless the majority of handsets share common characteristics and can be grouped into families. For example, all the devices made by a manufacturer or all the devices that provide certain functionalities. Device Grouping is useful as it provides a higher level of abstraction (in an specific context), avoiding to work with specific device instances or models.

Device Grouping is also a valuable tool for content adaptation on the Mobile Web. One significative example could be the dynamic generation of a web page that includes a game download menu. The version of each game to be offered to the user could depend on the manufacturer and memory restrictions imposed by the target device, among others. This particular application would benefit from the existence of a grouping mechanism. The developer could define different groups of devices specifying certain conditions to be met by the 'vendor' and 'availableMemory' property values.

Our problem could also have been solved by means of 'if' statements in any programming language (using the DDR Simple API). However such approach is unflexible as a change in the Group conditions would also imply a change in the application logic. Furthermore, "harcoded" Groups defined using programming language statements do not promote knowledge reuse between companies and organizations.

In order to promote a more flexible approach for Device Grouping, this W3C Note proposes an XML format, a syntax for group expressions (based on boolean conditions over the DDR properties) and an extension to the DDR Simple API.

Editorial Note : This Working Draft includes a preliminary, early proposal which it is expected to be taken over and revised by a successor of the DDWG.

2 Device Grouping based on XML

The device groups are defined in the XML format defined in the following sections. The XML infoset is described in XML Schema ... with each element in the http://www.w3.org/2008/05/ddr-structures namespace.

3 Extended Simple API

This note proposes two extensions to the DDR Simple API

public boolean belongsTo(Evidence evidence,String group);

4 Example

					
<deviceStructures xmlns="http://www.w3.org/2008/05/ddr-structures">
	<vocabularies>
		<vocabulary iri="http://www.w3.org/2008/01/DDR-Core-Vocabulary" nsPrefix="" />
		<vocabulary iri="http://example.org/vocabulary" nsPrefix="ex"/>
	</vocabularies>
	
	<groups>	
		<group id="NiceDevice">
			<expression>
				([imageFormatSupport,webBrowser] contains ('gif','jpeg') and [displayWidth] >= 240)
				or [ex:rendersTables,ex:webBrowser] == true and [inputDevices] contains ('touchScreen'))
			</expression>
		</group>
			
		<group id="XhtmlDevice">
			<expression>
				[markupSupport] contains ('xhtmlmp10','xhtmlbasic10')
			</expression>
		</group>		
	</groups>
</deviceStructures>
					
				

Properties props = new Properties();
props.put("org.w3c.ddr.structures","file:///structuresExample.xml");
ServiceExt service = (ServiceExt)ServiceFactory.newService(
	"org.example.DDRServiceExt","http://www.w3.org/2008/01/DDR-Core-Vocabulary",props);

Evidence evidence = service.newHttpEvidence();
evidence.put("User-Agent","Example Browser 1.1 on Example Device");						
if(service.belongsTo(evidence,"XhtmlDevice")) {
	// Do Something
}
else {
		// Do other
}