8. A method for comparing two structured documents, comprising: receiving information for a first document and a second document to be compared; traversing a first structure in the first document and a second structure in the second document to identify one or more potential matches between elements in the first and second documents; receiving, from a user, a request to specify at least custom rules defining expected differences between the first and second documents, the expected differences indicating a positional change between at least one actual element of the first document and at least one expected element of the second document, the first document having a first structure defining a first hierarchical arrangement of elements within the first document that includes the at least one actual element positioned within the first structure, the second document having a second structure defining a second hierarchical arrangement of elements within the second document that includes the at least one expected element positioned within the second structure, the expected differences indicating a structural difference between the first structure of the first document and the second structure of the second document; determining when differences between the identified potential matches are significant based at least in part on the custom rules, wherein significant differences are determined to be significant as a result of being differences that vary from the expected differences; and storing information for the at least one difference that is determined to be significant, according to configuration information specified by the user.
8. A method for comparing two structured documents, comprising: receiving information for a first document and a second document to be compared; traversing a first structure in the first document and a second structure in the second document to identify one or more potential matches between elements in the first and second documents; receiving, from a user, a request to specify at least custom rules defining expected differences between the first and second documents, the expected differences indicating a positional change between at least one actual element of the first document and at least one expected element of the second document, the first document having a first structure defining a first hierarchical arrangement of elements within the first document that includes the at least one actual element positioned within the first structure, the second document having a second structure defining a second hierarchical arrangement of elements within the second document that includes the at least one expected element positioned within the second structure, the expected differences indicating a structural difference between the first structure of the first document and the second structure of the second document; determining when differences between the identified potential matches are significant based at least in part on the custom rules, wherein significant differences are determined to be significant as a result of being differences that vary from the expected differences; and storing information for the at least one difference that is determined to be significant, according to configuration information specified by the user. 9. The method of claim 8 , wherein determining matches in the first and second documents occurs independently of variations in ordering of the first and second structures.