DDS15 — Syntax for Topic Names

For portability & interoperability it is necessary to know what the valid syntax of topic names can be, including valid characters. Some vendors support characters like '.' '/', ':' while others don't.

The spec should make clear which characters are supported by all vendors

Note that Appendix B does include a TOPICNAME syntax, but this section appears only related to content filters it is not clear if this would limit a Topic name in general. In Appendix B it says:

TOPICNAME - A topic name is an identifier for a topic, and is defined as any series of characters ‘a’, ..., ‘z’, ‘A’, ..., ‘Z’, ‘0’, ..., ‘9’, ‘-’ but may not start with a digit.

This seems limiting and also the "-" seems like an odd choice or perhaps a typo. "_" would be a more natural choice...

Also it seems very restrictive to not allow things like "." or "/" or ":" given that large systems would want to organize their topic names and take advantage of this.