Casing/delimiter style for attributes in events

[erkist]

In the Vocabulary Workgroup meeting July 27th we touched upon the topic of casing/delimiters for event attributes.

For top level attributes, CloudEvents enforces an "all lowercase letters and numbers only", but for the content of the data attribute (where we presumably would put all or most of our attributes) the CloudEvents specification does not provide any restrictions.

In the "Prior Arts" part of the Cloud Events primer several other event-like data structures are listed, and they seem to fall mostly into either the camelCase or the hyphen-separated category.

What do we want for our own attributes?