Per http://www.w3.org/TR/xquery-operators/#func-collection, fn:collection may be called with zero arguments. However, the following query
collection()
fails with SEDNA Message: ERROR XPST0017
It is a static error if the expanded QName and number of arguments in a function call do not match the name and arity of a function signature in the static context.
Details: http://www.w3.org/2005/xpath-functions:collection
I'd suggest that both collection() and collection(()) should return the set of standalone documents in the Sedna database.
Another possibility is that both of these could return the empty sequence, though that would be less useful.
Perhaps this bug is best fixed alongside bug ID 2839389, document-uri function does not yield useful result, once a decision is made about a scheme for Sedna document URIs.
Cheers
Justin Johansson
Anonymous
Justin, thanks for this bug report also ).