Dear André, thanks for your message. You write
The nLab is a very nice thing!
I am pleased to hear that you think working on such wikis may be worthwhile! That's very encouraging to hear, from somebody like you. The nLab is just a first, tiny and tentative step, but eventually, with more work, this kind of activity could be rather useful, I believe. You write:
Maybe you could create a wiki-lab for homotopy theory too (a HoLab?) Maybe all these labs could be connected.
Before I enter the technicalities of setting up separate wiki-labs below, let me ask you one question: as you indicate, one useful aspect of wiki material is its interconnectedness, via hyperlinks. I am imagining that eventually, with plenty of time, effort and contributors, a large web of wiki-material will grow, covering many parts of math and exhibiting their connectedness. For instance pure abstract category theory entries may point to entries about physics where the concepts are applied, and vice versa. We currently think of the nLab as a wiki to encompass all that, in principle -- being well aware, of course, that its current state is at best just a puny approximation to what it could be, eventually. So my question is: could you tell me what it is that makes you feel that topics like category theory or homotopy theory need to be more physically separated out of the nLab as a whole (if that's what you feel)? Could't you see a useful way that they exist as clusters of related entries inside the whole structure? This is at least currently the idea that we have: when clusters of entries corresponding to a given topic begin to accumulate, we currently try to equip them with shared "floating tables of contents" that give them a kind of sub-web existence within the nLab, without losing the close contact to the rest of the web. Such sub-clusters do currently include, among various others, the topics category theory -- http://ncatlab.org/nlab/show/category+theory+-+contents higher category theory -- http://ncatlab.org/nlab/show/higher+category+theory+-+contents We don't have as yet a reasonable such cluster on homotopy theory, though we have for instance the beginning of one on "abstract homotopy theory", i.e. model category theory -- http://ncatlab.org/nlab/show/model+category+theory+-+contents As I said, none of this is meant to be anything close to perfect, it's just to indicate seeds of possible structure within the nLab. So my gut reaction to your question would be: let's all improve and expand on the existing seeds of topic sub-clusters within the nLab, such as notably those on category theory! Let's not spread these efforts over too many different software installations. The more they are connected by one single web of links, the better. All this said, here is a little non-exhaustive bit of information on technicalities of setting up wiki-webs: what is straightforward is to branch off separate "instiki webs", as they are technically called, from the nLab. All these webs work just as the nLab itself does, they look and feel the same, and all run on the same software. Currently we follow the practice of offering personal webs to contributors who feel that they want to put material into the wiki, but in a more personal or private way than on the main nLab web. You can see the list of all sub-webs that current exist here: http://ncatlab.org/web_list http://ncatlab.org/nlabmeta/show/directory+of+personal+webs It is very easy to create such a sub-web titled "category theory" or "homotopy theory" or the like. If you do tell me that you would be likely to start adding material on, say, category theory, to such a sub-web "category theory", while not as likely to add the same material within the nLab web as such, I will be sure to take care that such a sub-web is created soon. But in that case, maybe we could jointly try to think about what would be necessary requirements, from your point of view, to instead keep all the material within the nLab itself. You see, in practice the main difference between two entries within the same web and two entries on different webs is, apart from maybe the color scheme of the entry header, just that hyperlinks within one web are easily and conveniently created -- one just types "[[keyword]]", while hyperlinks across webs are more tedious, one has to type "[[webname:keyword]]". The user who views these pages may not even be able to tell the difference, though! Finally, it is of course also possible to set up entirely separate installations of the wiki software. We are very lucky to have Andrew Stacey among us, who has the expertise and energy to handle such things. He is our software administrator, if you wish. Originally Jacques Distler helped us with these matters, but he is rather busy with lots of other things. If you think you would want an entire separate software installation of the wiki software on some server, then you should ask Andrew Stacey about this. If I remember well, he is already running a second wiki installation of the nLab kind for some other purpose. With best regards, Urs On Wed, Dec 23, 2009 at 8:10 PM, Joyal, André <joyal.andre@uqam.ca> wrote:
Dear Urs,
The nLab is a very nice thing!
http://ncatlab.org/nlab/show/HomePage
You wrote:
It is a wiki-lab for collaborative work on Mathematics, Physics and Philosophy especially from the n-point of view: insofar as these subjects touch on higher algebraic structures.
The nLab is devoting a lot of space to category theory. It would be nice to have a CatLab devoted to category theory per se. Is this something that can be created ? My knowledge of wiki-technology is null. Maybe you could create a wiki-lab for homotopy theory too (a HoLab?) Maybe all these labs could be connected.
Best, André
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