[css2] Incorporated Martins latest comments

ianbjacobs · ianbjacobs · commit 666a8dbec149 · 1998-02-11T23:42:16.000Z
--HG--
extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%40877
diff --git a/css2/syndata.src b/css2/syndata.src
@@ -1,6 +1,6 @@
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
 <html lang="en">
-<!-- $Id: syndata.src,v 2.5 1998-02-11 14:24:11 ijacobs Exp $ -->
+<!-- $Id: syndata.src,v 2.6 1998-02-11 23:42:16 ijacobs Exp $ -->
 <HEAD>
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <TITLE>CSS2 syntax and basic data types</TITLE>
@@ -154,8 +154,8 @@ href="#escaped-characters">escaped characters.</a>
     clear. There are two ways to do that:
 
     <ol>
-    <li>with a space (or other whitespace character): "\26 B" ("&B")
-    <li>by providing exactly 6 hexadecimal digits: "\000026B" ("&B")
+    <li>with a space (or other whitespace character): "\26 B" ("&amp;B")
+    <li>by providing exactly 6 hexadecimal digits: "\000026B" ("&amp;B")
     </ol>
 
     <p>In fact, the two methods may be combined. Only one whitespace
@@ -560,10 +560,10 @@ In CSS, the em-height is equal to the <span class="index-inst"
 title="font size">font size</span> used when rendering an element's
 text. It may be used for vertical or horizontal measurement. The 'ex'
 unit is equal to the font's <span class="index-def"
-title="x-height"><dfn>x-height</dfn></span> (the height of the letter
-'x') of the element's font. A font need not contain the letter "M" to
-have an 'em' size or the letter "x" to have an x-height; the font
-should still define the two units.
+title="x-height"><a name="x-height"><dfn>x-height</dfn></a></span>
+(the height of the letter 'x') of the element's font. A font need not
+contain the letter "M" to have an 'em' size or the letter "x" to have
+an x-height; the font should still define the two units.
 
 <!-- Incomplete -->
 
@@ -946,22 +946,20 @@ Character Set, defined in <a rel="biblioentry"
 href="./refs.html#ref-ISO10646">[ISO10646]</a>. For transmission and
 storage, these characters must be <span class="index-def"
 title="character encoding">encoded</span> by a character encoding that
-supports the ASCII character set (e.g., ISO 8859-x, SHIFT JIS, etc.).
-For a good introduction to character sets and character encodings,
-please consult <a rel="biblioentry" href="./refs.html#ref-HTML40"
-class="informref">[HTML40]</a>, Chapter 5.
+supports the set of characters available in US-ASCII (e.g., ISO
+8859-x, SHIFT JIS, etc.).  For a good introduction to character sets
+and character encodings, please consult <a rel="biblioentry"
+href="./refs.html#ref-HTML40" class="informref">[HTML40]</a>, Chapter
+5.
 
 <P>When a style sheet is embedded in another document, the style sheet
 shares the character encoding of the whole document. ("Embedded" here
 means textual inclusion, not embedded byte sequences.)  For
-example, in <a rel="biblioentry" href="./refs.html#ref-HTML40"
-class="informref">[HTML40]</a>, the "charset" attribute of many
-elements (META, LINK, A, etc.) designates the character encoding, as
-in:</p>
-
-<pre>
-&lt;META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt;
-</pre>
+information on character encoding specifications in HTML and XML
+respectively, please consult <a rel="biblioentry"
+href="./refs.html#ref-HTML40" class="informref">[HTML40]</a>, Chapter
+5 and <a rel="biblioentry" href="./refs.html#ref-XML10"
+class="informref">[XML10]</a>, Sections 2.2 and 4.3.3, and Appendix F.
 
 <P>When a style sheet resides in a separate file, user agents must
 observe the following <span class="index-inst" title="character
@@ -981,8 +979,8 @@ attribute of the LINK element).
 
 <P>When present, only one @charset rule may appear in an external
 style sheet -- it must <em>not</em> appear in an embedded style sheet
--- and it must be the first line in the document (not preceded by any
-other characters). After "@charset", authors specify the name of a
+-- and it must appear at the very start of the document, not preceded
+by any characters. After "@charset", authors specify the name of a
 character encoding. The name must be a charset name as described in <a
 href="refs.html#ref-IANA" class="normref">[IANA]</a> registry (see <a
 rel="biblioentry" href="./refs.html#ref-CHARSETS"
@@ -996,15 +994,14 @@ example:</p>
 <P>This specification does not mandate which character encodings
 a user agent must support.
 
-<P>What purpose does the @charset construct serve if user agents
-cannot understand it before they know the character encoding?  It acts
-as a verification mechanism. In the case HTTP headers do not provide
-character encoding information, user agents may attempt to guess the
-character set, and should they succeed, the @charset allows them to
-double check their guess. For this reason, character encodings in
-which the ASCII characters are encoded as themselves are more likely
-to help user agents determine the correct character encoding than
-other encodings schemes.
+<P>Note that reliance on the @charset construct theoretically poses a
+problem since there is no <em>a priori</em> information on how it is
+encoded. In practice, however, the encodings in wide use on the
+Internet are either based on ASCII, UTF-16, UCS-4, or (rarely) on
+EBCDIC.  This means that in general, the initial byte values of a
+document enable a user agent to detect the encoding family reliably,
+which provides enough information to decode the @charset rule, which
+in turn determines the exact character encoding.
 
 <!-- More examples of good encodings to use? -IJ -->
 
@@ -1016,15 +1013,15 @@ other encodings schemes.
 represented in the current character encoding.  These characters must
 be written as <a href="#escaped-characters">escaped</a> references to
 <a rel="biblioentry" href="./refs.html#ref-ISO10646">[ISO10646]</a>
-characters. These escapes are the equivalent of numeric character
+characters. These escapes serve the same purpose as numeric character
 references in HTML or XML documents (see <a rel="biblioentry"
 href="./refs.html#ref-HTML40">[HTML40], Chapters 5 and 25).</a>
 
 <P>The character escape mechanism should be used when only a few
 characters must be represented this way. If most of a document
 requires escaping, authors should encode it with a more appropriate
 encoding (e.g., if the document contains a lot of Greek characters,
-authors might use ISO 8859-7 or UTF 8).
+authors might use "ISO-8859-7" or "UTF-8").
 
 <P>Intermediate processors using a different character encoding may
 translate these escaped sequences into byte sequences of that
@@ -1046,20 +1043,21 @@ written as "\3BA\3BF\3C5\3C1\3BF\3C2".
 <em><strong>Note.</strong>
 In <a rel="biblioentry" href="./refs.html#ref-HTML40" 
 class="informref">[HTML40]</a>, 
-numeric character references may appear in "style" attribute
+numeric character references are interpreted in "style" attribute
 values but not in the content of the STYLE element. Because of this
 asymmetry, we recommend that authors use the CSS character 
-escape mechanism rather than numeric character references.
-For example, authors should write:</em></p>
+escape mechanism rather than numeric character references
+for both the "style" attribute and the STYLE element.
+For example, we recommend:</em></p>
 
 <pre class="html-example">
-   &lt;SPAN style="voice-family: D\FCrst"&gt;...&lt;/SPAN&gt;
+   &lt;SPAN style="voice-family: D\FC rst"&gt;...&lt;/SPAN&gt;
 </pre>
 
 <P><em>rather than:</em></p>
 
 <pre class="html-example">
-   &lt;SPAN style="voice-family: D&amp;amp;#FC;rst"&gt;...&lt;/SPAN&gt;
+   &lt;SPAN style="voice-family: D&amp;#FC;rst"&gt;...&lt;/SPAN&gt;
 </pre>
 </div>
 
