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http://www.cse.unsw.edu.au/~willu/ 2009-10-08 07:26:01 -04:00 committed by Joey Hess
parent 808c699961
commit 57d694046f
1 changed files with 37 additions and 9 deletions
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doc/todo/dependency_types.mdwn
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@ -239,6 +239,21 @@ sigh.
>>> Hmm, I'm not seeing cycles be a problem, at least with the current
>>> pagespec terms. --[[Joey]]
>>>> Oh, they're not with current pagespec terms. But this is really close to extending to handle
>>>> functional pagespecs, etc. And I think I'd like to think about that now.
>>>>
>>>> Having said that, I don't want to hold you up - you seem to be making progress. The best is
>>>> the enemy of the good, etc. etc.
>>>>
>>>> For my part, I'm imagining we have two more constructs in IkiWiki:
>>>>
>>>> * A map directive that actually wikilinks to the pages it links to, and
>>>> * A `match_sharedLink(pageX)` matching function that matches pageY if both pageX and pageY each have links to any same third page, pageZ.
>>>>
>>>> With those two constructs, one page changing might change the set of pages included in a map somewhere, which might then change the set of pages matched by some other pagespec, which might then...
>>>>
>>>> --[[Will]]
----
### Link dependencies
@ -313,16 +328,13 @@ can indirectly influence what pages a pagespec matches.
> Trying to make a formal definition of this: (Note, I'm using the term sets rather than lists, but they're roughly equivalent)
>
> * Let the *matching set* for a pagespec be the set of pages that the pagespec matches.
> * Let a *complete influence set* for a pagespec be the set of all pages whose alteration might change the matching set of that pagespec.
> * Let the *direct influence set* be the intersection of the matching set and the complete influence set.
> * Let the *indirect influence set* be the compliment of the direct influence set with respect to the complete influence set.
> * Let the *matching set* for a pagespec be the set of existing pages that the pagespec matches.
> * Let a *influence set* for a pagespec be the set of all pages, *p*, whose alteration might:
> * cause the pagespec to include or exclude a page other than *p*, or
> * cause the pagespec to exclude *p*.
>
>> \[Will snipped some stuff and edited the formal definition]
>
> Is that a fair definition? I don't think it quite matches your examples below unfortunately.
> I was unsure if I should insert the word 'existing' in there in a few places. As it stands, these definitions could include sets of pages that don't exist, e.g. "*".
> The one I'm least sure of is the definition of the direct influence set. It feels like you want something
> like "the traditional set of things we thought about that could cause a pagespec to change", but that definition
> is not very formal and I suspect will lead to problems. Something like "The set of pages matched by the globs in the pagespec" might be closer?
> --[[Will]]
>> I appreciate the formalism!
@ -331,11 +343,24 @@ can indirectly influence what pages a pagespec matches.
>> in the future, the existing dependency code will always test to see
>> if it matches. So it will be in the maching set (or not) at that point.
>>
>>> Hrm, I agree with you in general, but I think I can come up with nasty counter-examples. What about a pagespec
>>> of "!backlink(bogus)" where the page bogus doesn't exist? In this case, the page 'bogus' needs to be in the influence
>>> set even though it doesn't exist.
>>>
>>> Also, I would really like the formalism to include the whole dependency system, not just any additions to it. That will make
>>> the whole thing much easier to reason about.
>>
>> The problem with your definition of direct influence set seems to be
>> that it doesn't allow `link()` and `title()` to have as an indirect
>> influence, the page that matches. But I'm quite sure we need those.
>> --[[Joey]]
>>> I see what you mean. Does the revised definition capture this effectively?
>>> The problem with this revised definition is that it still doesn't match your examples below.
>>> My revised definition will include pretty much all currently matching pages to be in the influence list
>>> because deletion of any of them would cause a change in which pages are matched - the removal problem.
>>> -- [[Will]]
#### Examples
* The pagespec "created_before(foo)" has an influence list that contains foo.
@ -349,6 +374,9 @@ can indirectly influence what pages a pagespec matches.
Avoiding including every page in the wiki into its influence list is
very important!
>>> So, why don't the above influence lists contain the currently matched pages?
>>> Don't you need this to handle the removal problem? -- [[Will]]
* The pagespec "title(foo)" has an influence list that contains every page
that currently matches it. A change to any matching page can change its
title, making it not match any more, and so the list is needed due to the