# Extensions

The full library of Saxon and EXSLT functions described in extensions.html is available, except for those (such as `saxon:serialize`) that have an intrinsic dependency on an XSLT stylesheet.

An XQuery pragma is defined allowing a default value to be specified for a query parameter (external variable). The syntax is illustrated below:

    declare namespace saxon="http://saxon.sf.net/";
    declare variable $x external (:: pragma saxon:default "20" ::);

The default value must be either a numeric literal or a string literal.

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