Ignore:
Timestamp:
Jan 25, 2013, 5:29:05 AM (7 years ago)
Author:
fielding@…
Message:

reduce Accept-Language priority to a note about how some recipients treat the list as ordered and how user agents adjust to that by sending both distinct qvalues and list them in descending order; addresses #428

File:
1 edited

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  • draft-ietf-httpbis/latest/p2-semantics.html

    r2162 r2163  
    20052005      </p>
    20062006      <div id="rfc.figure.u.33"></div><pre class="text">  Accept-Language: da, en-gb;q=0.8, en;q=0.7
    2007 </pre><p id="rfc.section.5.3.5.p.5">would mean: "I prefer Danish, but will accept British English and other types of English". If no quality values are assigned
    2008          or multiple language tags have been assigned the same quality, the same-weighted languages are listed in descending order
    2009          of priority. Additional discussion of language priority lists can be found in <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>.
    2010       </p>
    2011       <p id="rfc.section.5.3.5.p.6">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements. The
     2007</pre><p id="rfc.section.5.3.5.p.5">would mean: "I prefer Danish, but will accept British English and other types of English".</p>
     2008      <p id="rfc.section.5.3.5.p.6">Note that some recipients treat the order in which language tags are listed as an indication of descending priority, particularly
     2009         for tags that are assigned equal quality values (no value is the same as q=1). However, this behavior cannot be relied upon.
     2010         For consistency and to maximize interoperability, many user agents assign each language tag a unique quality value while also
     2011         listing them in order of decreasing quality. Additional discussion of language priority lists can be found in <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>.
     2012      </p>
     2013      <p id="rfc.section.5.3.5.p.7">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements. The
    20122014         "Basic Filtering" scheme (<a href="#RFC4647" id="rfc.xref.RFC4647.4"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-3.3.1">Section 3.3.1</a>) is identical to the matching scheme that was previously defined for HTTP in <a href="http://tools.ietf.org/html/rfc2616#section-14.4">Section 14.4</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    20132015      </p>
    2014       <p id="rfc.section.5.3.5.p.7">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
     2016      <p id="rfc.section.5.3.5.p.8">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
    20152017         preferences of the user in every request (<a href="#fingerprinting" title="Browser Fingerprinting">Section&nbsp;9.6</a>).
    20162018      </p>
    2017       <p id="rfc.section.5.3.5.p.8">Since intelligibility is highly dependent on the individual user, user agents need to allow user control over the linguistic
     2019      <p id="rfc.section.5.3.5.p.9">Since intelligibility is highly dependent on the individual user, user agents need to allow user control over the linguistic
    20182020         preference. A user agent that does not provide such control to the user <em class="bcp14">MUST NOT</em> send an Accept-Language header field.
    20192021      </p>
    2020       <div class="note" id="rfc.section.5.3.5.p.9">
     2022      <div class="note" id="rfc.section.5.3.5.p.10">
    20212023         <p> <b>Note:</b> User agents ought to provide guidance to users when setting a preference, since users are rarely familiar with the details
    20222024            of language matching as described above. For example, users might assume that on selecting "en-gb", they will be served any
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