Deciding on value classes for various nodes

[VisLab]

There are several decisions about value classes that need to be finalized before full-support of value classes can be implemented.

One problem is that for these items:

Item/Object/Man-made-object/Device/IO-device/Input-device/Keyboard/Keyboard-key/#
Item/Object/Man-made-object/Device/IO-device/Input-device/Keypad/Keypad-key/#

It isn't clear what class they should be in. HED allowedCharacter never allows a comma. Parsers are guaranteed that a comma will always be a separator. Thus we need a mechanism for deciding how to specify more general characters that aren't in the standard ASCII. We could use a unicode or UTF-8 quoting mechanism of some kind.

Another issue is the posixPath value class. This value class is meant for terms such as Metadata/Pathname/#:

Property/Informational-property/Metadata/Pathname/#

While posixPath has a tentative specification, it was removed as an attribute of Pathname prior to Version 8.0.0 release because the current specification of posixPath does not account for all possible path names that we want to allow. This is an item for future work and discussion.