
RFID MIDDLEWARE 149
public String getStandardVersion( ) throws SecurityException;
// Returns the version number of the ALE Specification
public String getVendorVersion( ) throws SecurityException;
// Returns the version number relevant to the vendor
}
Usage Scenarios
As discussed earlier, the ALE specification supports both synchronous and asynchronous
models of interaction between the clients and the ALE service. Now that we have seen the
ALE interface API, let’s look at how these interaction models are intended to be used. We’ll
also develop a deeper understanding of some of the key components of the ALE schema.
Synchronous mode
Let’s start by looking at how a client would make a one-time request for events coming
from a set of Readers and, along the way, specifying how the raw EPC observations should
be filtered and grouped. The ALE specification calls this mode of interaction “immediate.”
Immediate mode.
Immediate mode is one of the two synchronous methods available to
access an ALE service. The client first creates and configures an ECSpec, and then invokes
the “immediate” service of the ALE server. The ALESpec looks at the ECSpec that is passed
as a parameter of the immediate service. As shown in the previous section, “Data elements,”
the ECSpec specifies a list of Readers from which the client wants to receive events. It also
specifies the event cycle boundaries (in the boundary object) ...