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Showing <code>nofollow</code> in conjunction with [[votelinks]], and applying it in parallel with [[ | Showing <code>nofollow</code> in conjunction with [[votelinks]], and applying it in parallel with [[rel-nofollow]]: | ||
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Revision as of 19:37, 13 November 2007
Robot Exclusion Profile
Draft Specification 2005-06-18
Authors
Copyright
This specification is © 2004-2005 by the author. However, the author intends to submit this specification to a standards body with a liberal copyright/licensing policy such as the GMPG. See the GMPG Principles for more details. Anyone wishing to contribute to this effort MUST read those principles, especially those regarding copyright and licensing, and agree to them before contributing.
Patents
The author neither holds nor intends to apply for any patents on anything required to implement this specification.
Abstract
The Robot Exclusion Profile is a reworking of the Robots META tag (and less-standard extensions) as a microformat.
Introduction
The Robots META tag is used to provide page-specific direction for web crawlers. While being useful in many cases, its page-specific nature means it cannot be used to restrict crawlers from indexing only certain sections of a document. Several attempts have been made to create more granular solutions through various methods but have perceived shortcomings that limit their use; the Robot Exclusion Profile defines a microformat that can be applied to any element or set of elements in a page.
Like other microformats such as hCalendar, the Robot Exclusion Profile defines a set of class names that may be applied to (X)HTML elements. class can be applied to almost every (X)HTML element, which means that authors may be as specific or general as they wish in their application. This differs from the similarly-purposed rel="nofollow" attribute, which may only be applied to (and does not refer to the content of) a specific inline link. (It is interesting to note that this behavior is entirely encompassed by the use of class="robots-nofollow" on the same element.) Classes are also additive, so multiple values can be specified at once, e.g. class="robots-nofollow robots-noindex". For robot exclusion in particular, this allows authors to specify multiple rules for an element without adding unnecessary extra markup.
Format
Profile URI
http://example.org/xmdp/robots-profile# (obviously placeholder)
The classes defined by the Robot Exclusion Profile should be considered meaningless when the profile URI is not present in the document <head>'s profile attribute.
XMDP Profile
<dl class="profile"> <dt id="robots-nofollow">robots-nofollow</dt> <dd> Informs robots that links contained by the element are not to be followed. </dd> <dt id="robots-follow">robots-follow</dt> <dd> Informs robots that links contained by the element are to be followed. </dd> <dt id="robots-noindex">robots-noindex</dt> <dd> Informs robots that the content of the element is not to be included as part of the page. </dd> <dt id="robots-index">robots-index</dt> <dd> Informs robots that the content of the element is to be included as part of the page. </dd> <dt id="robots-noanchortext">robots-noanchortext</dt> <dd> Informs robots that the link target document is not to be indexed under the anchor text. </dd> <dt id="robots-anchortext">robots-anchortext</dt> <dd> Informs robots that the link target document is to be indexed under the anchor text. </dd> <dt id="robots-noarchive">robots-noarchive</dt> <dd> Informs caching robots that the content of the element is not to be included in their cached copy. </dd> <dt id="robots-archive">robots-archive</dt> <dd> Informs caching robots that the content of the element is to be included in their cached copy. </dd> </dl>
Examples
Removing page content:
<head profile=”http://example.org/xmdp/robots-profile#”> ... <div class=”robots-noindex”>There once was a man from Nantucket…</div> <p>This page is not about <span class=”robots-noindex”>pornography</span>.</p>
Showing nofollow in conjunction with votelinks, and applying it in parallel with rel-nofollow:
<head profile=”http://example.org/xmdp/robots-profile#”>
...
<p class=”robots-nofollow”>This is <a href=”http://example.com/bogus”>a bogus link</a>
and so is <a href=”http://example.net/bogus”>this</a>.</p>
<p>I don't like <a rel="nofollow" rev="vote-against" class="robots-nofollow"
href="http://example.com/disagree">this page</a>
but I do like <a rev="vote-for" href="http://example.com/agree">this one</a>.</p>
Preventing images from being stored by search engines, forcing them to be retrieved from the originating website:
<head profile="http://example.org/xmdp/robots-profile#"> ... <p><img src="example.png" class="robots-noarchive" alt="Private image" /></p>
A consequence of this is that the small summaries that modern search engines display with the result links also exclude the robots-noarchive. We suggest replacing small excluded segments with an ellipsis [...]. Unarchived segments of a size comparable to the segments the search engine normally uses for summaries can just be omitted. Probably a display of an entire cached document which has unarchived segments should also include some locution to show the places where text has been elided, no matter what the size.
A more complex example is available which also shows how the robots metadata may be visualized.
References
Normative
Informative
- A Standard for Robot Exclusion
- Googlebot Frequently Asked Questions
- The ROBOTS META Tag
- RelNoFollow Draft Specification
- This page was contributed from the technorati developers' wiki.