be shown in search results. Most search engines support the Canonical link element as a hint to which URL should be treated as the true version. As indicated by John Mueller of Google, having other directives in a page, like the robots noindex element can give search engines conflicting signals about how to handle canonicalization Example: http://wikipedia.com http://www.wikipedia.com http://www.wikipedia.com/ http://www.wikipedia.com/?source=asdf All of these URLs point to the homepage of Wikipedia, but a search engine will only consider one of them to be the canonical form of the URL. XML A Canonical XML document is by definition an XML document that is in XML Canonical form, defined by The Canonical XML specification. Briefly, canonicalization removes whitespace within tags, uses particular character encodings, sorts namespace references and eliminates redundant ones, removes XML and DOCTYPE declarations, and transforms relative URIs into absolute URIs. A simple example would be the following two snippets of XML: <code><node1 x='1' a="1" a="2">Data</node1 > Data</code> Data Data The first example contains extra spaces in the closing tag of the first node. The second example, which has been canonicalized, has had these spaces removed. Note that only the spaces within the tags are removed under W3C canonicalization, not those between tags. A full summary of canonicalization changes is listed below: The document is encoded in UTF-8 Line breaks normalized to #xA on input, before parsing Attribute values are normalized, as if by a validating processor Character and parsed entity references are replaced CDATA sections are replaced with their character content The XML declaration and document type declaration are removed Empty elements are converted to start-end tag pairs Whitespace outside of the document element and within start and end tags is normalized All whitespace in character content is retained (excluding characters removed during line feed normalization) Attribute value delimiters are set to quotation marks (double quotes) Special characters in attribute values and character content are replaced by character references Superfluous namespace declarations are removed from each element Default attributes are added to each element Fixup of xml:base attributes is performed Lexicographic order is imposed on the namespace declarations and attributes of each element Computational linguistics In morphology and lexicography, a lemma is the canonical form of a set of words. In English, for example, run, runs, ran, and running are forms of the same lexeme, so we can select one of them; ex. run, to represent all the forms. Lexical