A few comments inside.
On 12 Nov 2003, at 14:34, Sylvain Wallez wrote:
Unico Hommes wrote:
<snip/>
1/ Virtual components
Virtual components are sitemap snippets that can be used in place of "regular" components. I many languages, these are called "macros". With sitemap statements as components, virtual components are a breeze to implement: just lookup the component, and see if what's returned is a regular sitemap component (e.g. a Serializer) or if it's a ProcessingNode. If it's a regular sitemap component, add it to the pipeline, and otherwise invoke the ProcessingNode.
What I'm not sure about here, is if its possible (or even desirable) that we can have two different implementation interfaces for a single role.
The problem with Fortress here is that it forces the role to be the implementation interface. It is also due to the way Fortress handles meta data.
Can't virtual components just implement their respective pipeline component interfaces: Transformer, Generator, Serializer? This way we'd treat them just as regular pipeline components.
The problem of virtual components is that they have to add components to the pipeline that's being built (e.g. a virtual serializer will add zero or more transformers and a serializer).
Why don't we use virtual component just like what they are: an assembly of components that, from the outside, look just like another component? it feels like we hardwire the various components into one an expose that as it was a regular component.
Sounds elegant to me.
The only way in which they can implement the regular interface (e.g. Serializer) is by creating a local internal pipeline that will be connected to the global one. But it looks like going this way will require heavy complex changes in the pipeline machinery that I think should be avoided.
I'm might be underestimating the required changes, but why is it so? [curious more than anything]
So the immediate - but looking hacky - solution that comes to mind is for virtual components to implement the regular component interface for the sake of Fortress compatibility, but refuse the corresponding methods (throw UnsupportedOperationException) and implement an additional "VirtualComponent" interface that provides a buildPipeline(Pipeline) method.
Yuck!! there must be a better way of doing this, c'mon!
Mmmh... more thinking is required here.
<snip/>
Side note: relative URIs
------------------------
The various considerations about inheritance above leads to the question of resolution of relative source URI (Carsten raised this issue some time ago): what is the base URI that should be used by the resolver?
My opinion is that the base URI should be the one of the sitemap _handling_ the request. This means that "jumping" to another sitemap through virtual components or view inheritance should not affect the base URI.
However, there are many situations where we want to use a source relative to the _current_ sitemap regardless on how it's called. For this, I propose a new protocol similar to how "context:" behaves with the root sitemap, but for non-root sitemaps. The "sitemap:" protocol comes to mind, but I'm not sure this is a good name.
Wild idea: context:/ identifies the current context, context:// identifies the root sitemap? Like in cocoon: protocol?
Great idea (again!). Currently, the "context:" protocol requires the double-slash and links to the root sitemap, so we can implement this additional behaviour with a single slash with no compatibility break. And the similarity with "cocoon:" makes it easy to understand.
+1
This makes me think that "cocoon:" must also be be relative to the "current" sitemap, and not that handling the request.
Uh? this is not the case already? if so, +1 for the change.
<snip/>
Conclusion
----------
This new approach seems to have very few drawbacks (hope I did not miss something important), and will lead to a dramatic simplification of the sitemap engine. The most noticeable one being that the number of classes will be divided by 2.
Cool I am glad you say this. I was starting to think I was just shooting my mouth off. (Which off course I was but somehow turned out alright ;-)
Sometimes, wild idea that others do not answer prove to have a great future. An noticeable example is the flowscript: Ovidiu started to hack some Lisp in a little corner of the scratchpad, and this led to a major new feature!
True. The benefit of this community is that nobody is really attached to his/her code. We value challenges and wild thinking more than we value self pride.
I'm happy (but this feeling is shared by everyone around here) everytime I'm proven wrong and I can learn something, or improve my reasoning, my code or my behavior.
So, keep it up ;-)
<snip/>
I agree with Carsten that we should develop it in 2.2 and see later if we can port it to ECM so it's useable from 2.1 as well.
Ok. A backport is always possible.
+1 for 2.2 as well!
And I also think we should consider this approach when migrating Woody to CocoonForms, since Woody uses the same mechanism than the TreeProcessor to build a widget definition trees.
Thanks again Unico for this brillant idea.
Actually, Sylvain, I wasn't trying to solve all the things you said this idea now solves. Nope, don't blame me ;-)
Well, so just go on throwing wild ideas and let others analyze their potential implications ;-)
Ok, now the admin part: Sylvain, Unico, are you volunteering to implement all this? ;-)
Berin, do you have a little time to help them on Fortress needs would they emerge?
-- Stefano.
