Re: [XBL] Complexity of XBL

On Wed, 6 Dec 2006, Cyril Concolato wrote:
> 
> As a general comment, I think the binding mechanism is really 
> interesting but the specification requires complex algorithms which may 
> not be needed in many scenarios. Among the complex algorithms:
>
> - explicit/implicit inheritance: what will be the percentage of content 
> really using this feature ?

Based on implementation experience with XBL1 in the Mozilla world, it's 
heavily used.


> - runtime behavior: the specification requires to be able to detach a 
> binding. This means that the original structure of the bound element 
> needs to be kept, thus an heavy memory usage.

Yes. However, the dynamic nature of the Web is such that this is 
definitely required. For example, changing skins (again, look at Mozilla 
XUL for an example).


> - attach/regenerate bidings: this may require a lot of processing and 
> the feature may not be heavily used.

Not sure what you mean here.


> - live binding and document: the specification says:
>    "Dynamic changes to shadow content templates are reflected in bindings."
>    "An imported binding document is live."
>    "All of the nodes in the shadow tree are live."
>    "Whenever the subtree of a template element is dynamically modified, any
>     shadow trees that were constructed by cloning that element must be
>     regenerated."
> It also allows modifying the "extends" attribute. All this processing 
> seems really heavy.

It is basically required by the DOM, which is, by design, live.


> Has the WG evaluated the cost of all these features and weighted the cost
> versus benefits? It would be very interesting to see the results.

I do not believe any formal analysis has been made, but Mozilla has been 
shipping XBL1 for years and XBL2's design is heavily influenced by the 
experience gained from XBL1's implementation and use.


> Has the WG considered making simple profiles of this specification ?

Profiles of content languages like this are very bad design and lead to 
walled-garden environments.

Cheers,
-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

Received on Monday, 8 January 2007 21:49:53 UTC