Restrictions on label naming

[Shaun Lumley]

Receiving an error on generation of a Page Properties Report for label sp-release. Altering a couple Page Properties and the Page Properties Report to the label sp-releas displays those properties correctly in the report. I've looked into other causes, but want to rule out label name restrictions.

1. Is sp-release a restricted label name?
2. Are there any label name restrictions (ie. cannot start with a number, no punctuation, etc.), and where are they documented?

[Shaun Lumley]

This is for Confluence 5.9