From the page WikiPortal, a NaturalPortal would be analogous to an Alexandrian "centre" or a graph centre or the "balancing point". It essentially is a place in the PageDatabase that has the property of being central to the page graph (probably the centre of the graph). These portals aren't constructed by a ForwardIndex or a ReverseIndex, but they arise naturally as people make links as they write. One argument is that these NaturalPortal""s are more indicative of what's important on the site.

An idea from WikiPortal, you can calculate NaturalPortal""s without taking the artificially-constructed forward and reverse indices into account. The argument is that the artificial portals taint the calculation. Detecting what constitutes a forward or reverse index is another problem. You can either do this functionally, say by excluding pages that are adjacent to 10% of the site, or you can do this editorially by flagging the pages like we have done here with CategoryHomePage. I've had to escape the link because pages that link to CategoryHomePage are excluded from certain IndexingSchemes.