The pattern allows strings matching the following EBNF: TopicPathExpression ::= TopicPath ( '|' TopicPath )* TopicPath ::= RootTopic ChildTopicExpression* RootTopic ::= (QName | '*') ChildTopicExpression ::= '/' (NCName | '*' | ‘/*’) The pattern allows strings matching the following EBNF: ConcreteTopicPath ::= RootTopic ChildTopic* RootTopic ::= QName ChildTopic ::= '/' NCName