Matthias:

Both properties InputNode and NormalState have a value of the data
type NodeId. The NodeIds are referring to the Variable nodes
containing the Input Value and the NormalState Value. These two values
of the referenced variable are compared.

If this is not clear from the text we need to improve it.

Jouni Aro:
Yes, I think it needs a bit clarification. I did get the idea, but not from the specification text, so I was not sure about.

It also appeared that my customer had not understood it, and asked me for a clarification about how is it supposed to work, but I had to ask you. :)

Having read it once more, I think I got the problem sorted out.

If you say that InputNode Property is compared to NormalState Property, everything is clear, assuming that one understands that InputNode Property is the value of the property referenced by InputNode...ehm...property (which is a NodeId, referring to the InputNode Property).

But the specification is not consistent in the use of these terms:

"When the value of the Variable referenced by the InputNode Property is not equal to the value of the NormalState Property the Alarm is active."

The necessary indirection makes it more complicated than it needs to be (as usual).