The Web so far has been incredibly successful at deliveringinformation to human users. So successful actually, that there is now anurgent need to go beyond a browsing human and make informationaccessible to applications, in order to offer automation,inter-operation and Web-awareness among services. To do so, informationfrom Web sources needs to be accessible in a structured way. XML and itsvarious extensions (data-models, query languages) are a step in thisdirection. Unfortunately, the Web is not yet a well organized repositoryof nicely structured XML documents but rather a conglomerate of volatileHTML pages, for which structure has to be extracted. To address thisproblem, we present the World Wide Web Wrapper Factory (W4F), a Javatoolkit for the generation of wrappers for Web sources. Our maincontributions are: (1) an expressive language to specify the extractionof complex structures from HTML pages; (2) a declarative mapping to XMLdocuments, with the automatic generation of the corresponding DTDs; (3)some visual supports to make the engineering of wrappers faster andeasier As an illustration, we show how we can, via W4F intermediation,transparently query HTML sources from an XML query language
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