Question:

I have 10 "bracketed" variables ("[EVENT]", "[PROTOCOL]", "[SESSION]", etc...) I need to restrict an attribute. Valid cases are:

<ol><li>Any string without brackets </li> <li>Mentioned 10 "bracketed" variables</li> <li>Any bracketed variable(s) concatenated with regular strings, for example: My[EVENT]<em>for</em>[PROTOCOL]@google.com</li> <li>Empty string</li> </ol>

Non-valid cases:

<ol><li>Any string inside brackets, except 10 predefined</li> <li>The same with concatenations </li> <li>Strings with only opening or closing bracket </li> </ol>

To be short - inside brackets only predefined variables are allowed and they can be concatenated with any string.

Thanks in advance

Read the regular expression as follows: <strong><em>The concatenation of one or more substrings containing no brackets except for those surrounding EVENT, PROTOCOL, or SESSION.</em></strong> This is trivially extended to additional acceptable bracketed variables.

<?xml version="1.0" encoding="utf-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="root"> <xs:complexType> <xs:attribute name="attr"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:pattern value="[^\[\]]*"/> <xs:pattern value="([^\[\]]*\[(EVENT|PROTOCOL|SESSION)\][^\[\]]*)+"/> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> </xs:schema>