Abstract-The first phase of reverse engineering of weboriented applications is the extraction of concepts hidden in HTML pages including tables, lists and forms, or marked in XML documents. In this paper, we present an approach to index semantically these two sources of information (HTML page and XML document) using on the one hand, domain ontology to validate the extracted concepts and on the other hand the similarity measurement between ontology concepts with the aim of enrichment the index. This approach will be conceived in three steps (modeling, attaching and Enrichment) and thereafter, it will be realized and implemented by examples. The obtained results lead to better re-engineering of web applications and subsequently a distinguished improvement in the web structuring.