The Identifier property is a read/write string that is used to identify an application to the servers to which it connects. Typically this string will contain a GUID in registry format, for example: 3509D21C-C73C-4246-BEE2-7F39D741DF2B
Servers can use this identifier to provide information regarding the kinds of applications that are connecting at any particular time.
The object placeholder is an object expression that evaluates to an object that supports the IPIAppIdentity interface. Currently this is only the PISDK object.
An application should always use the same GUID when setting this property. A unique GUID for an application can be obtained using the Microsoft program Guidgen.exe
It is possible for an application to have more than one identifier. For example an application can contain a control that talks to the SDK. The control can set an identifier in its code while the application can also specify an identifier. The server will see both of these identifiers associated with a particular session. Duplicate identifiers are discarded so, although logically you only need to set the identifier once, resetting it to the same value during an execution is not a problem.
Server functionality to accept and record these identifiers was introduced in PI3.3 SR1. Earlier servers will ignore the information.