|
What is the Application Level Events (ALE) Preview for RFID?
This technology preview is based on the interface and the XML query language defined by the EPCglobal Application Level Events (ALE) 1.0 specification. ALE allows a client application to submit questions about EPC read events to a network of reader points. In most cases, read points will be RFID readers, although the ALE specification does not actually mandate the use of RFID readers for capturing EPC data. An example of such a question is "Which EPCs issued by IBM are in warehouse A?"
ALE also provides a mechanism for evaluating such questions on an ad hoc basis (that is, in a request-response paradigm) or as a standing request (that is: submit once, get notifications when appropriate).
The main benefit of ALE is facilitation of application development that relies on EPC data input for making business decisions. Without a mechanism such as ALE, access to a network of readers would be a tedious task that would involve accessing various readers through low-level APIs, sorting through the individual read events, aggregating them as appropriate for a given business purpose, and exposing the resulting information to an interested client application. With ALE, the client application can abstract most of these tasks. It must simply compose an XML document and hand it over to a generic engine for interpretation and execution. Thus, ALE allows application developers to focus on the business task at hand and leave the technical details surrounding EPC data input to a dedicated software component. The latest version of the ALE specification can be obtained from the EPCglobal Web site.
How does it work?
Applications that require EPC/RFID (Electronic Product Code/Radio Frequency Identification) data from readers interact with the corresponding ALE Engine that is processing EPC/RFID data from those readers. The interaction involves different steps depending on whether it's a standing request or an ad hoc request. In the case of a standing request, the application defines an event cycle specification at the ALE Engine. This specification includes details such as readers of interest, when to start the data collection cycle, when to terminate it, and the report format. The application later subscribes to the event cycle specification and provides the recipient with event cycle reports. This subscription activates the event cycle specification and starts an event cycle when specified starting conditions are met. When stop conditions are met, the ALE Engine generates an event cycle report and sends it to all subscribers. This cycle is repeated as long as the event cycle specification is subscribed to. When the application no longer needs event cycle reports from this specification, it unsubscribes to it. It could resubscribe to the specification at a later time. When it no longer needs the event cycle specification, it undefines the specification and thus removes it from the ALE Engine.
In order to use this technology, one must develop a client to interact with the ALE Engine. At this time, ALE Engine supports the SOAP protocol and provides WSDL for generating client code. This client is used to interact with the ALE Engine as defined above. In addition, one must define one or more components that provide EPC tag data to the ALE Engine using the XML/HTTP protocol and a format defined in the user guide. One also must define a component that can provide start and stop triggers via HTTP Post messages as defined in the user's guide.
This technology preview kit includes a JavaScript-based client application that allows creation and local storage of event cycle specifications; interaction with the ALE Engine using a browser; and reception of event cycle reports from the ALE Engine. The preview kit also includes RFID and a trigger simulator. The user's guide provides examples and step-by-step instructions on the use of the client applications and the simulator.
In a typical deployment, an ALE Engine processes EPC/RFID data coming from multiple readers.
|
View screenshots:
