A unified generic method for the vector based graphic recognition is presented．The scheme consists of two main steps：finding the first key component and extending it according to the specific graphic syntax．A new spatial data structure，the position index，which facilitates the search for the constituent primitives in given areas，is devised to realize the mapping from planar positions to graphic primitives．Two applica-tions，dashed line detection and hatching lines detection，are also presented as two cases in point．