Just like the Reader Protocol described earlier, the reader
management speci?¬?es three distinct layers:
. Reader layer
. Messaging layer
. Transport layer
However, unlike the Reader Protocol, three message channels are used. The ?¬?rst is the
control channel; the second is the noti?¬?cation channel; and the third (and new channel) is
one or more alarm channels (which carries alarms issued asynchronously from the reader
to the host). The speci?¬?cation de?¬?nes a number of objects and commands along with their
parameters (data ?¬?elds).
2.9 Application Layer Events
The Application Layer Events Speci?¬?cation (EPCglobal, 2005d) provides an interface
through which clients may obtain ?¬?ltered, consolidated EPC data from a variety of sources.
In most EPC processing systems, there is a level of processing that reduces the volume of
data that comes directly from EPC data sources such as RFID readers into coarser ??????events??™??™
of interest to applications. The processing done at this layer typically involves:
. Receiving EPCs from one or more data sources such as readers
. Accumulating data over intervals of time, ?¬?ltering to eliminate duplicate EPCs and
EPCs that are not of interest, and counting and grouping EPCs to reduce the
volume of data
. Reporting in various forms
28 RFID Handbook: Applications, Technology, Security, and Privacy
The ALE interface has a number of features:
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