2007/5/12, Fabrice Colin <<a href="mailto:fabrice.colin@gmail.com">fabrice.colin@gmail.com</a>>:<div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> On 5/12/07, Mikkel Kamstrup Erlandsen <<a href="mailto:mikkel.kamstrup@gmail.com">mikkel.kamstrup@gmail.com</a>> wrote: > 2007/5/12, Fabrice Colin <<a href="mailto:fabrice.colin@gmail.com">fabrice.colin@gmail.com </a>>: > > I am not sure I understand the benefit of defining these in some sort > > of user-editable configuration, instead of in a spec. > > If the user defines a new field, it won't have any effect as the engine has > > no way to automagically know how that new field maps to the underlying > > file format. The corresponding metadata extractor will have to be updated > > to support the new field and make sure it is retrieved from files. > > It was not the idea that an ordinary user should install field definitions. > Applications with special needs could do so, but most wouldn't need to. Do I > understand correctly in that you don't see the need to have the ontology > defined in a machine readable way? Just specced out in some document? While > this could be done, the machine readable ontology does have quite a few > benefits. Fx: > >  * You could update the ontology without updating any applications or search > engine code > >  * 3rd parties could extend the ontology by installing their own ones > Yes, you could update or extend the ontology, but the new fields won't be automatically populated until the engine is told how to get those from the original data. Does this make sense ?</blockquote><div> Yes you are entirely right. There are still many reasons to allow for extensibility though. It might be that some search engines will extract more rich data than the xesam spec. With easily introspectable fields applications can pick this up on the fly. It has also been discussed several times how to use common metadata extractors. If applications could install a special-purpose extractor then we also need a way to define new fields... Cheers, Mikkel </div> </div>