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Message-ID: <2313595.P6UQk0Ptvu@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Sun, 06 Nov 2011 21:11 +0100
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Subject: Re: Code not working
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Jukka K. Korpela wrote:

> […] Thomas 'PointedEars' Lahn [wrote]:
>> Jukka K. Korpela wrote:
>>> 11/5/2011 6:15 PM, Luuk wrote:
>>>>> <script type="text/javscript">
>>>> you are missing an 'a' in 'javascript'
>>> This illustrates why it is better to write just<script>, unless company
>>> police forces you to conform to formal specs that make the type
>>> attribute required (for no good reason).
>>
>> No, it illustrates that a markup validator is to be used (before
>> publishing content).
> 
> No markup validator reports <script type="text/javscript"> as an error

AISB, you will have to prove your assertions if you want to be taken 
seriously.

> (because it is not a reportable markup error). 

You are wrong.

The HTML 4.01 and 5 (Draft) Specifications state that the value of the 
`type' attribute of the `script' element must be a "(valid MIME/)content 
type" [1,2] (from here: MIME type).  A valid MIME type should not only 
conform to syntactical requirements for MIME types (although the HTML5 draft 
states that this suffices [2]), but it should also be registered with IANA 
[10], which limits the acceptable attribute values.

The set of MIME types that are reasonable to use here is further limited by 
the element type.  A markup validator could (indeed, it should) report at 
least a warning for a non-registered MIME type such as "text/javscript", as 
their use is "discouraged" by RFC 2616 [3], which HTML 4.01 through RFCs 
2045 and 2046 [4], and HTML5 directly [5], refer to.

Since the W3C Markup Validator already does experimental markup validation 
that is not based on a DTD, for HTML5 [6] (because there is no HTML5 DTD 
[7]), it is not too much of a stretch to expect it to report that as an 
error or at least issue a warning.  Unfortunately, it does neither for now;
but other validators might do that already, and the W3C Markup Validator 
could do that in the future.  The set of registered MIME types, especially 
the set of programming languages that can be used for client-side scripting 
from within (X)HTML (or SVG), does not change so often to make it 
unfeasible.

In addition to hard-coded validation, it is also possible to validate XHTML, 
the XHTML syntax of HTML5 or any other XML-based document against an XML 
Schema Definition (cf. [8,9]).  XML Schema allows the definition of 
restrictions for attribute values so that `type="text/javscript"' would not 
pass validation.  For a simple example ([8] slightly adapted):

  …

  <xs:simpleType name="ScriptType">
    <xs:annotation>
      <xs:documentation>
        Media types for ECMAScript implementations, as per [RFC 4329]
      </xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:string">
      <xsd:enumeration value="application/ecmascript"/>
      <xsd:enumeration value="application/javascript"/>
      <xsd:enumeration value="text/ecmascript"/>
      <xsd:enumeration value="text/javascript"/>
    </xs:restriction>
  </xs:simpleType>  

  …

  <xs:element name="script">
    <xs:annotation>
      <xs:documentation>
        script statements, which may include CDATA sections
      </xs:documentation>
    </xs:annotation>
    <xs:complexType mixed="true">
      <xs:attribute name="id" type="xs:ID"/>
      <xs:attribute name="charset" type="Charset"/>
      <xs:attribute name="type" use="required" type="ScriptType"/>
      <xs:attribute name="src" type="URI"/>
      <xs:attribute name="defer">
        <xs:simpleType>
          <xs:restriction base="xs:token">
            <xs:enumeration value="defer"/>
          </xs:restriction>
        </xs:simpleType>
      </xs:attribute>
      <xs:attribute ref="xml:space" fixed="preserve"/>
    </xs:complexType>
  </xs:element>

For maximum flexibility, such a Schema or an equivalent list of acceptable 
MIME types could be generated from [10] or resources such as /etc/mime.types 
dynamically, or updated regularly.

So in fact there are various ways, including those mentioned, that allow 
such errors in attribute values to be flagged upon markup validation.


PointedEars
___________
 [1] <http://www.w3.org/TR/html401/interact/scripts.html#adef-type-SCRIPT>
 [2] <http://dev.w3.org/html5/spec/scripting-1.html#attr-script-type>
 [3] <http://tools.ietf.org/html/rfc2616#section-3.7>
 [4] <http://www.w3.org/TR/html401/types.html#h-6.7>
 [5] <http://dev.w3.org/html5/spec/infrastructure.html#valid-mime-type>
 [6] <http://validator.w3.org/whatsnew.html>, "2008-11-20 — 0.8.4 release"
 [7] <http://dev.w3.org/html5/spec/syntax.html#the-doctype>
 [8] <http://www.w3.org/TR/xhtml1-schema/>
 [9] <http://schneegans.de/sv/>
[10] <http://www.iana.org/assignments/media-types/index.html>
-- 
Danny Goodman's books are out of date and teach practices that are
positively harmful for cross-browser scripting.
 -- Richard Cornford, cljs, <cife6q$253$1$8300dec7@news.demon.co.uk> (2004)