XML has become the standard format for web publishing and data exchange on the Internet. Much research has been done to provide efficient access to relevant information that is ubiquitous on the Web. In this paper, we present an algorithm to find a sequence of top-down edit operations with minimum cost that transforms an XML document such that it conforms to a schema. The minimum cost is based on the tree edit distance with top-down edit operations. It is shown that the algorithm runs in O(p × log p × n), where p is the size of the schema(grammar) and n is the size of the XML document(tree).