In an embodiment, an XPath automaton with state look-ahead capability can efficiently determine whether XML documents, received in a stream in serialized form in a network element, match any of a set of XPath expressions. A token processor receives a structured electronic document in serialized format and identifies entities. A name recognition engine recognizes names of elements of the document and recognizes names of attributes of the elements. A finite state automaton comprises states and transitions representing structural relationships among elements and attributes of structured path expressions and state look-ahead logic that is configured to output a final state when an entity matches one or more of the structured path expressions. The automaton performs state transitions resulting in reaching a specified final state if a match to an expression occurs.