If you do not specify a rule set name when you create a validator for an object, the Validation block will, by default, apply all rules that have no name (effectively, rules with an empty string as the name) that it can find in
configuration, attributes, and self-validation. If you have specified one rule set in configuration as the default rule set for the type you are validating (by setting the DefaultRule property for that type to the rule set name), rules within this rule set
are also treated as being members of the default (unnamed) rule set.
However, an empty ruleset name or remove the name attribute makes the configuration invalid and it will not load.
The following ruleset definitions are not is not valid