Add recommendation for key naming?

[psss]

Currently there is no recommendation about how an attribute key should look like. For example if there is a need for key consisting of multiple words what would be the best choice?

Keeping spaces? Which could possibly cause problems if not handled properly?

/smoke:
    summary: Basic smoke test
    tcms id: TC#1234567

Substituting them with dashes?

/smoke:
    summary: Basic smoke test
    tcms-id: TC#1234567

Or underscores?

/smoke:
    summary: Basic smoke test
    tcms_id: TC#1234567

Or give no recommendation at all? Ideas?

[AloisMahdal]

no recommendation at all

because it must be obvious to most what is the correct_way, adn the rest is doomed :)