[dbaron revision history] Add back much of conformance section. (date: 2004/05/03 18:46:39)

Author: dbaron

css3-syntax/Overview.src.html

@@ -1063,6 +1063,133 @@ <h3>Historical notes</h3>
   <li><em>-wap-</em> (The WAP Forum)</li>
 </ul>
 
+<h2 id="conf">Conformance</h2>
+
+<p>The key words <dfn>"MUST"</dfn>,
+<dfn>"MUST NOT"</dfn>, <dfn>"REQUIRED"</dfn>, <dfn>"SHALL"</dfn>, <dfn
+>"SHALL NOT"</dfn>, <dfn>"SHOULD"</dfn>, <dfn>"SHOULD NOT"</dfn>,
+<dfn>"RECOMMENDED"</dfn>, <dfn>"MAY"</dfn>, and <dfn>"OPTIONAL"</dfn> in this document
+are to be interpreted as described in RFC&nbsp;2119 (see [[!RFC2119]]).
+However, for readability, these words do not appear in all uppercase
+letters in this specification.</p>
+
+<h3>Definitions</h3>
+
+<p class="issue">[Some of these need heavy rewriting given
+modularization.  I've avoided substituting CSS3 where it's clearly not
+going to be appropriate.]</p>
+
+<p>This module and other CSS3 modules rely on the following
+definitions:</p>
+
+<dl>
+
+<dt><dfn>Style sheet</dfn>
+
+<dd>A set of statements that specify presentation of a document.
+
+<p>Style sheets may have three different origins: <a
+href="#author">author</a>, <a href="#user">user</a>, and <a
+href="#user-agent">user agent</a>. The interaction of these sources is
+described in the cascading and
+inheritance module [[!CSS3CASCADE]].</p>
+
+<dt><dfn>Valid style sheet</dfn>
+
+<dd>The validity of a style sheet depends on the level of CSS
+used for the style sheet. All valid CSS1 style sheets are valid CSS&nbsp;2.1
+style sheets, but some changes from CSS1 mean that
+a few CSS1 style sheets will have slightly different semantics in
+CSS&nbsp;2.1. Some features in CSS2 are not part of CSS&nbsp;2.1, so not all CSS2
+style sheets are valid CSS&nbsp;2.1 style sheets.
+
+<P>A valid CSS&nbsp;2.1 style sheet must be written according to the <a
+href="#detailed-grammar">grammar of CSS&nbsp;2.1</a>. Furthermore, it must contain
+only at-rules, property names, and property values defined in this
+specification. An <dfn>illegal</dfn> (invalid) at-rule,
+property name, or property value is one that is not valid.
+
+<dt><dfn>Ignore</dfn>
+
+<dd>This term has three slightly different meanings in this specification.
+First, a CSS parser must follow certain rules when it discovers unknown
+or illegal syntax in a style sheet. The parser must then ignore certain
+parts of the style sheets. The exact rules for what parts must be
+ignored is given in these section: <a href="#declaration">Declarations
+and properties</a>, <a href="#error-handling">Rules for handling parsing
+errors</a>, <a href="#unsupportedvalues">Unsupported Values</a>, or may be
+explained in the text where the term "ignore" appears. Second, a user
+agent may (and, in some cases must) disregard certain properties or
+values in the style sheet even if the syntax is legal. For example,
+table-column-group elements cannot have borders around them, so the
+border properties must be ignored.
+
+<dt><dfn>Author</dfn>
+<dd>An author is a person who writes
+documents and associated style sheets. An 
+<dfn>authoring tool</dfn>
+generates documents and associated style sheets.</dd>
+
+<dt><dfn>User</dfn> 
+<dd> A user is a person who interacts with a user agent to view, hear, or
+otherwise use a document and its associated style sheet. The user
+may provide a personal style sheet that encodes personal
+preferences.
+</dd>
+
+<dt><dfn>User agent (UA)</dfn>
+<dd>A <dfn title="user agent|UA">user
+agent</dfn> is any program that interprets a document written in
+the document language and applies associated style sheets according
+to the terms of this specification. A user agent may display a
+document, read it aloud, cause it to be printed, convert it
+to another format, etc.</dd>
+
+<DD>An HTML user agent is one that supports the HTML 2.x, HTML 3.x, or
+HTML 4.x specifications. A user agent that supports XHTML [[XHTML10]],
+but not HTML (as listed in the previous sentence) is not considered an
+HTML user agent for the purpose of conformance with this
+specification.
+
+</dl>
+
+
+<h3 id="conf-UA">User agent conformance</h3>
+
+<p class="issue">[This section should contain rules for user style sheet
+conformance, author style sheet disabling, handling parsing errors,
+etc., from the CSS2.1 specification.]</p>
+
+
+<h4>Error conditions</h4>
+
+<P>In general, this document does not specify error handling behavior
+for user agents (e.g., how they behave when they cannot find
+a resource designated by a URI).
+
+<P>However, user agents must observe the <a
+href="#error-handling">rules for handling parsing errors</a>.
+
+<P>Since user agents may vary in how they handle error conditions,
+authors and users must not rely on specific error recovery behavior.
+
+
+<h3 id="conf-SS">Style sheet conformance</h3>
+
+<h3 id="conf-AT">Authoring tool conformance</h3>
+
+<p>Authoring tools may use a modified form of the <a
+href="#error-handling">rules for handling parsing errors</a>:  when
+those rules require that user agents <em>ignore</em> something,
+authoring tools are not required to ignore it.  However, authoring tools
+should not present such parts of the style sheet to the user in the same
+way as valid parts of the style sheet.  In so far as authoring tools
+display the application of a style sheet to a document, they are required
+to meet the <a href="#conf-UA">user agent conformance</a> rules.</p>
+
+<p class="issue">[informative reference to canonicalization proposal?]</p>
+
+
 <h2 id="property-defs">Format of property definitions in other modules</h2>
 
 <p>Each CSS property definition begins with a summary of key