"Directed cyclic graph" is a mathematical term describing the nature of the Wikipedia category system.  In non-mathematical terms, "graph" means it's a collection of objects (categories) with links ("category A is a subcategory of category B") between them, "cyclic" means that there are places where you can go from "A" to "B" to "C" to "A" by following those links (a category can be a subcategory of itself), and "directed" means those links are not symmetrical (that is, if category "A" is a subcategory of "B", it doesn't mean that "B" is a subcategory of "A").

-- 
Mark

On Wed, May 29, 2013 at 3:59 PM, Luigi Assom <luigi.assom@gmail.com> wrote:
Hi Brad,
actually is there a schema of the graph?
you said "directed", hence there should some hierarchy in it too.'
I read there are 50K+ categories, maybe is there any list of "directions" aka "links" of how categories are connected?


On Wed, May 29, 2013 at 10:51 PM, Brad Jorsch <bjorsch@wikimedia.org> wrote:
On Wed, May 29, 2013 at 4:33 PM, Pavan Kapanipathi <pavan@knoesis.org> wrote:
> Hi,
> Whats the simplest way to extract complete and the latest Wikipedia Category
> Hierarchy?

Note that the "category hierarchy" isn't much of a hierarchy; it's a
directed graph with cycles and no particular root.

Your best bet is probably to download a database dump from
http://dumps.wikimedia.org/enwiki/latest/ and process it.


--
Brad Jorsch
Software Engineer
Wikimedia Foundation

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--
Luigi Assom

Skype contact: oggigigi

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