Non-element Selectors extends [SELECTORS4] and allow selecting other kinds of document nodes than elements. This is useful when selectors are used as a general document query language.
Non-element Selectors are not intended to be used in CSS, but only as a separate query language in other host environments.
CSS is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.
Status of this document
This is a public copy of the editors’ draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don’t cite this document other than as work in progress.
GitHub Issues are preferred for discussion of this specification.
When filing an issue, please put the text “selectors-nonelement” in the title,
preferably like this:
“[selectors-nonelement] …summary of comment…”.
All issues and comments are archived,
and there is also a historical archive.
Selectors are a very popular mechanism for selecting things in HTML and XML content.
They are not used only in CSS [CSS3SYN] but also as a standalone query language in libraries like jQuery,
in newer standardized browser APIs like [SELECTORS-API] and in other Web standards like ITS 2.0.
The [SELECTORS4] specification only defines selectors for selecting element nodes from the document,
but some uses of Selectors would like to select other types of nodes as well.
This specification extends [SELECTORS4] with additional selectors
that can be used for selecting non-element nodes in a document tree.
Note: Currently the draft only defines means for selecting and matching attribute nodes,
but other kinds of nodes, such as comments or processing instructions, might be supported in the future.
2. Non-element Selectors
2.1. Attribute node selector
An attribute node selector represents an attribute node in a document tree.
Its syntax is:
<namespace-attr> is divided into two halves:
an optional prefix preceding a '|' character,
and an attribute name following it.
If the <na-prefix> is provided as an <ident>,
it must match a declared namespace prefix,
in which case the selector only matches attributes in that namespace;
if it doesn’t match a declared namespace prefix,
the selector matches nothing.
If the <na-prefix> is provided as a * character,
the selector matches attributes in any namespace.
If the <na-prefix> is omitted,
the selector only matches attributes in no namespace.
If the <na-name> is an <ident>,
the selector matches attributes with that name.
If the <na-name> is a * character,
the selector matches attributes with any name.
If the <namespace-attr> is omitted entirely,
the selector matches any attribute in any namespace.
The selector matches an attribute node with the given namespace and name on the originating element,
if such an attribute exists.
Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. [RFC2119]
Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with class="example",
This is an example of an informative example.
Informative notes begin with the word “Note” and are set apart from the
normative text with class="note", like this:
Note, this is an informative note.
Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <strong class="advisement">, like
this: UAs MUST provide an accessible alternative.
Conformance to this specification
is defined for three conformance classes:
A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
Requirements for Responsible Implementation of CSS
The following sections define several conformance requirements
for implementing CSS responsibly,
in a way that promotes interoperability in the present and future.
So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid
(and ignore as appropriate)
any at-rules, properties, property values, keywords, and other syntactic constructs
for which they have no usable level of support.
In particular, user agents must not selectively ignore
unsupported property values and honor supported values in a single multi-value property declaration:
if any value is considered invalid (as unsupported values must be),
CSS requires that the entire declaration be ignored.
Implementations of Unstable and Proprietary Features
Once a specification reaches the Candidate Recommendation stage,
implementers should release an unprefixed implementation
of any CR-level feature they can demonstrate
to be correctly implemented according to spec,
and should avoid exposing a prefixed variant of that feature.
To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS