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POXSD restriction that negates a matching string
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  1. POXSD restriction that negates a matching string
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    copied!<p>I want my XSD to validate the contents of a string. To be specific, I want to validate <strong>that a certain string does not occur</strong>. </p> <p>Consider this rule, which will verify that my string occurs. Looking for all <code>Link</code>elements starts with this particular string: <code>/site/example.com</code> </p> <pre><code>&lt;xs:element name="Link" type="xs:normalizedString" minOccurs="0"&gt; &lt;xs:simpleType&gt; &lt;xs:restriction base="xs:token"&gt; &lt;xs:pattern value="(/site/example\.com).*"/&gt; &lt;/xs:restriction&gt; &lt;/xs:simpleType&gt; &lt;/xs:element&gt; </code></pre> <p>In other words, the expression above verifies that all <code>Link</code> elements start with <code>/site/example.com</code>. How do you invert the expression above, so that it **verifies that no <code>Link</code> elements start with <code>/site/example.com</code>? </p> <p>I tried the following regexp with no luck: <code>/[^(site/example\.com)].*</code>, so this is not working: </p> <p> </p> <p><strong>Not-working strategy 1 (negation of single character)</strong> I am aware that this probably would work for negating a single character, since this SO question does that: <a href="https://stackoverflow.com/questions/6014507/xml-schema-restriction-pattern-for-not-allowing-empty-strings">XML schema restriction pattern for not allowing empty strings</a></p> <p>The suggested pattern in that question <code>&lt;xs:pattern value=".*[^\s].*" /&gt;</code></p> <p>But negating only a single character does not work in this case, since it would correctly fail:</p> <blockquote> <p>/site/example.com</p> </blockquote> <p>but also it would incorrectly fail</p> <blockquote> <p>/solutions</p> </blockquote> <p><strong>Not-working Strategy 2 (advanced regexp lookahead)</strong> According to this SO question ( <a href="https://stackoverflow.com/questions/406230/regular-expression-to-match-string-not-containing-a-word">Regular expression to match a line that doesn&#39;t contain a word?</a> ), you could solve this with negative lookahead <code>(?!expr)</code>.</p> <p>So this will work in ordinary regexp:</p> <blockquote> <p>^((?!/site/example.com).)*$</p> </blockquote> <p>Now, unfortunately xsd validations support only limited regexps. According to this site, no lookaheads are supported: <a href="http://www.regular-expressions.info/xml.html" rel="nofollow noreferrer">regular-expressions.info -- xsd</a></p> <p>This pretty much describes what i have tried until now.</p> <p>My question is, how do i negate a regular expression in an XSD schema?</p>
 

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