Such rfid tags and visual codes such codes and sema codes

This record is optional and can be used to hold one or more MIME type image records so that the device reading the Smart Poster record can include one of those images (depending upon its capabilities) in the URI display.

21.2.2.5.5 Size Record

The Contactless Communication API, or JSR-257 [7], allows applications to access infor-mation on contactless targets, such as RFID tags and visual codes such as QR codes and sema codes [8]. The 2D barcodes are similar to RFID tags in that they contain data often in the form of a URL. However, they hold much smaller amounts of information than the newer RFID tags and they are generally slower and more difficult to read [9].

The primary objective of JSR-257 is to provide easy access to various contactless targets and transfer information to or from them. Before we provide details of programming RFID=NFC applications we shall first consider the mandatory and optional parts of the API, which are divided into five packages as shown in Figure 21.7 [7].

Discoverymanager 1

«interface» «interface» «interface» «interface»Visual tag connection 5 Plain tag connection 3 ISO14443 connection 4 NDEF tag connection 2

Symbology manager 5 Package legend

FIGURE 21.7
Overview of JSR 257 Reference Specification.

application to receive notifications about targets in close vicinity an application must obtain an instance of the DiscoveryManager class which in return provides the notific-ations to application about contactless targets. An application can then use subpackages to communicate with different targets depending upon their type. Connections to contactless targets are built on top of Generic Connection Framework (GCF). Each target defines a new protocol to GCF, although only the visual code protocol is visible and all RFID related protocols are hidden due to the nature of communication involved.