Rename PropertyIdentifier to be consistent with ASHRAE Standard

[guangyuzhang]

Hello Joel,

As an entry level BACnet developer, I found it's a little hard to read the code against with the Standard because the PropertyIdentifiers are different in them. For example, the code uses 'presentValue', 'statusFlags', the standard uses 'Present_Value', 'Status_Flags'.

I understand it's hard to refactor the code, but it will be helpful.

Thanks,
Guangyu Zhang

[JoelBender]

It's worse than that, the Examples uses object types in all uppercase like ANALOG_INPUT and property names in quotes like Object_Identifier and Annex Y uses the ASN.1 names like analog-input and present-value. There is a basic ambiguity if Object_Identifier would refer to the property name or the class of all object identifiers, and having the "BACnet" prefix in front of all of the class names (itself a convention that was born out of adopting ASN.1 and the subsequent syntax requirements) seemed excessive in the world of object oriented programming. Of course "-" is not a valid character identifier in a vast majority of the programming languages, and many shops have been opposed to the underscore, which is not as big a deal these days as it used to be (like encoding the data type as a prefix for property/attribute names).

I proposed making an editorial change to the standard to make them all consistent and programmer friendly; UpperCamelCase names for things and lowerCamelCase names for properties. Because every API and tool kits makes its own decisions about naming conventions, this was regarded as ultimately a lot of work for very little gain.

Because Annex Y references ASN.1 names, and BACnet Web Services does as well, I also use present-value RDF predicate names expecting that it will be a little easier to get approved. At this point changing the ASN.1 productions would break other conventions, so at this point it's just one of those things to get used to.