Does ShavedByBob.mdwn include itself?
-(Yeah - in IkiWiki currently links are included by include, but the idea holds. I had a good example a while back, but I can't think of it right now.)
+(Yeah - in IkiWiki currently links are *not* included by include, but the idea holds. I had a good example a while back, but I can't think of it right now.)
sigh.
> to determine what metadata, pages, etc they depend on. It is indeed
> tricky to do. More thoughts on influence lists a bit below. --[[Joey]]
+>> The big part of what makes this tricky is that there may be cycles in the
+>> dependency graph. This can lead to situations where the result is just not
+>> well defined. This is what I was trying to get at above. -- [[Will]]
+
+>>> Hmm, I'm not seeing cycles be a problem, at least with the current
+>>> pagespec terms. --[[Joey]]
+
----
### Link dependencies
* `add_depends($page, $spec, links => 1, presence => 1)`
adds a links + presence dependency.
-* `refresh` only rebuilds a page with a links dependency if
- pages matched by the pagespec gain or lose links. (What the link
- actually points to may change independent of this, due to changes
- elsewhere, without it firing.)
+* Use backlinks change code to detect changes to link dependencies too.
* So, brokenlinks can fire whenever any links in any of the
pages it's tracking change, or when pages are added or
removed.
that currently match it. If the list changes, the dependency is triggered.
Should be doable, but may involve more work than
-currently. Consider that a dependency on "bugs/*" currently
+currently. Consider that a dependency on `bugs/*` currently
is triggered by just checking until *one* page is found to match it.
But to store the list, *every* page would have to be tried against it.
Unless the list can somehow be intelligently updated, looking at only the
I'm using this term for the concept of a list of pages whose modification
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.
+>
+> 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!
+>>
+>> Only existing pages need to be in these sets, because if a page is added
+>> 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.
+>>
+>> 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]]
+
#### Examples
* The pagespec "created_before(foo)" has an influence list that contains foo.
* 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. Why is that considered an indirect influence? Well, the pagespec
- might be used in a presence dependency, and so its title changing
- would not directly affect the dependency.
+ title, making it not match any more, and so the list is needed due to the
+ removal problem.
* The pagespec "backlink(index)" has an influence list
that contains index (because a change to index changes the backlinks).
remove a link and make it not match any more, and so the list is needed
due to the removal problem.
+>> Why doesn't this include every page? If I change a page that doesn't have a link to
+>> 'done' to include a link to 'done', then it will now match... or is that considered a
+>> 'direct match'? -- [[Will]]
+
+>>> The regular dependency calculation code will check if every changed
+>>> page matches every dependency. So it will notice the link was added.
+>>> --[[Joey]]
+
#### Low-level Calculation
One way to calculate a pagespec's influence would be to
onto the influence list. If we combine the influences from each
successful match, we get the right result.
-> This is implemented, seems to work ok. --[[Joey]]
+> This is implemented, seems to work ok. --[[Joey]]
-#### High-level Calculation and Storage
+> `or` short-circuits too, but the implementation correctly uses `|`,
+> which I assume is what you meant. --[[smcv]]
-Calculating the full influence list for a pagespec requires trying to match
-it against every page in the wiki.
+#### High-level Calculation and Storage
-I'd like to avoid doing such expensive matching redundantly. So add a
-`pagespec_match_all`, which returns a list of all pages in the whole
-wiki that match the pagespec, and also adds the pagespec as a dependency,
-and while it's at it, calculates and stores the influence list.
+Naively calculating the full influence list for a pagespec requires trying
+to match it against every page in the wiki. I'd like to avoid doing such
+expensive matching redundantly.
+
+It may be possible, for some types of pagespecs, to just try matching a
+single, arbitrary page against it, and know the full influence list has
+been obtained. It seems to be that case that if a pagespec has any
+influences, matching any page will return at least one. So if none are
+returned, we can skip trying other pages.
+
+If the influence list does not include the page that was tried, we know
+that the pagespec does not things like `link()` and `title()`, that are
+influenced by the page's own content. So it *might* be safe to not try
+matching any more pages in this case too. I think it would work for all
+current pagespec terms. There might be a hypothetical term where this
+optimisation doesn't work. We could add a special case to ensure it can
+work: If a term declares it is unfluenced by "", then it means it is
+always influenced by the matching page.
+
+Anyway, this seems worth doing: Add a `pagespec_match_all`, which returns a
+list of all pages in the whole wiki that match the pagespec, and also adds
+the pagespec as a dependency, and while it's at it, calculates and stores
+the influence list.
It could have an optional sort parameter, and limit parameter, to control
how many items to return and the sort order. So when inline wants to
regular list of simple dependencies. So, the data stored ends up looking
just like what is stored today by the explicit dependency hacks. Except,
it's calculated more smartly, and is added automatically.
+
+> I've implemented influence calculation in `add_depends`. As expected,
+> it means rather a lot more work, and makes some things much slower.
+> Optimisations next.. --[[Joey]]
+
+#### Influence types
+
+Note that influences can also have types, same as dependency types.
+For example, "backlink(foo)" has an influence of foo, of type links.
+"created_before(foo)" also is influenced by foo, but it's a presence
+type. Etc.
+
+> This is an interesting concept that I hadn't considered. It might
+> allow significant computational savings, but I suspect will be tricky
+> to implement. -- [[Will]]
+
+>> It was actually really easy to implement it, assuming I picked the right
+>> dependency types of course. --[[Joey]]