[whatwg] Citing multiple <blockquote> elements in HTML5
Calogero Alex Baldacchino
alex.baldacchino at email.it
Sun Dec 7 18:20:18 PST 2008
Ian Hickson ha scritto:
> What terminology would you prefer rather than "subtree"? (We can't say
> document, since we are also trying to define conformance rules for
> disconnected subtrees handled from scripts.)
I was thinking again on that. Let me suggest something like the
following (and just do suggest, I'm far from wishing to impose my point
of view, and don't want to be pedantic, but I belive deeply exploring
every alternative may improve the specification).
"The _id_ attribute represents an element unique identifier in the
subtree within which the element finds itself and must contain at least
one character. In this context, a subtree is either a whole document
tree, or a tree of Node instances containing HTMLElements and
disconnected from any HTML document; a subtree of a document tree is
contained in a subtree of the first type, thus id values must be unique
in the containing document (e.g. a duplicate id inside a document tree
is always illegal, even if a branch of the document can be isolated
where the id is unique, unless such branch is removed from the document).
This specification requires the _id_ attribute value to be unique in a
subtree of the former type, thus a subtree of the latter type (e.g. a
document fragment manipulated by a script) to be inserted into an HTML
document must fulfil such requirement, as well as any other requirements
defined in this specification for conformance purpose. Any API dealing
with ID properties in any type of subtree must consider the _id_
attribute value of an HTMLElement as the element's default ID property;
however, this specification doesn't preclude an element having multiple
IDs, if other, API-specific mechanisms can set an element's ID in a way
that doesn't conflict with the id attribute" - then the rest.
One rational for the above is that, formally, a subtree disconnected
from any actual HTML document might be out of scope for current
specification, which defines conformance rules for HTML documents and
related contexts (such as a script context or a browsing context, both
applying to a 'connected' subtree, as far as I've understood), while a
subtree which is disconnected from a specific HTML document, but is
contained into another one (thus coinciding with the containing document
tree) is yet covered by the constraint for whole documents.
Another rational is that current specification, while relying on at
least one method affected by IDs uniqueness in a document tree (that is,
DOM Core Document.getElementById), does not provide, nor refers to, any
API which might be directly affected by the uniqueness of an id
attribute value in a disconnected subtree, thus such an API may be
indirectly related to id values uniqueness if ID properties are relevant
for its facilities, but the subtree itself cannot be constrained by
conformance rules before its insertion into an actual HTML document.
A further rational is that a disconnected subtree might contain Node
instances not implementing the HTMLElement interface, such as a
DocumentFragment node, but also MathML/SVG elements, which might be
embedded content elements coming from an HTML document tree, but also
from a document of a different kind where the embedded content was
represented by HTML elements, thus, without a sure knowledge on the
subtree origin, applying an HTML-specific conformance rule might not be
a correct choice, until the subtree is to be inserted into an HTML document.
For the question related to space characters inside an id value, I'd
"An ID property is not expected to contain space characters, so the
value of an _id_ attribute should not contain any space characters.
However, an id attribute can hold a decoded fragment identifier value
for the purpose of same-document references, thus space characters are
tolerated for the purpose of conformance, in order to avoid applying
restrictions to an otherwise legal fragment identifier value not being
part of a _URL_."
Everything, of course, IMHO.
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