Automatically maintaining wrappers for semi-structured web sources

In order to let software programs gain full benefit from semi-structured web sources, wrapper programs must be built to provide a “machine-readable” view over them. Wrappers are able to accept a query against the source and return a set of structured results, thus enabling applications to access web data in a similar manner to that of information from databases. A significant problem in this approach arises as Web sources may undergo changes that invalidate the current wrappers. In this paper, we present novel heuristics and algorithms to address this problem. In our approach the system collects some query results during normal wrapper operation and, when the source changes, it uses them as input to generate a set of labeled examples for the source which can then be used to induce a new wrapper.