Echelon LonBridg Server - Manual (Page 31)

LonBridge Server User’s Guide 25
retrieves the id attribute; you can also view the id attribute in the devices.xml
file (see Instances Directory on page 16).
Expressions
Expressions are used in the where attribute of the message. The
conditional operators include:
• and
• or
• >
• >=
• ==
• !=
Operators are processed from left to right. However, you can use parentheses to
group conditions.
Tracers
A tracer is a special attribute that you can use to identify a specific message, so
that the LonBridge application can filter the message response from other
responses it receives. A tracer is any attribute that includes an underscore (_)
prefix. You can use tracers for LonBridge API messages (called message tracers )
or for a LonBridge device class file (called node tracers ).
Example for a message tracer:
_mytracetimestamp="090803121356"/>
...
_mytracetimestamp="090803121356"/>
Subsequent queries do not return the same tracers:
...
Errors
The LonBridge Server reports errors using the element. The
element contains a message that describes the error. There are no fixed
attributes for the element.