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What is Application Level Events
Overview
Application Level Events (ALE) is a standard created by EPCGlobal, Inc., an organization of industry leaders devoted to the development of standards for the Electronic Product Code (EPC) and Radio Frequency Identification (RFID) technologies. The ALE specification is a software specification indicating required functionality and behavior, as well as a common API expressed through XML Schema Definition (XSD) and Web Services Description Language (WSDL).

The behavior expressed through the ALE specification is a way to provided aggregation and filtering of tag data over a period of time. An ALE server allows you to specify when to start collecting data, when to stop collecting data, how to organize and sort the dataand when to send the data to interested parties. An ALE client allows you to communicate with any compatible ALE server to define data requirements and receive reports.

What Challenges Does ALE Help Overcome?
RFID has the potential to generate a massive amount of data in a typical production environment.If you have an environment with tens or hundreds of readers with each reader reading a number of tags at a low interval (polling at 250 milliseconds or in continuous mode where the reader just streams all tags it sees continually), you can see how the amount of data a business application would have to process can become unwieldy. If an application is not written in a manner to handle this large throughput of data, it can suffer severescalability problems, perform poorly, or at worst, crash.

This is where the ALE specification comes in. It defines a configurable set of data gathering techniques that higher order business applications can then use to receive more specialized set of tags to process. ALE provides for a standard way to describe and define these data gathering techniques to help decouple a business application from the source of its RFID data.