XML Schema Pattern Error

Question

I am trying to write an XML schema. The specifics require me to validate a field so that it starts with a letter, followed by alphanumeric characters (e.g. Foo3x4 is valid, 3Foo or Foo3_ are not).

This is how I wrote it:

<xsd:simpleType name="nameType">
    <xsd:restriction base="xsd:string">
        <xsd:pattern value="^[a-zA-z][a-zA-Z0-9]*$" />
    </xsd:restriction>
</xsd:simpleType>

But if I try to validate a document that has as nameType the value H0, it gives me the following error (translated in English by me):

cvc-pattern-valid: The value "H0" is not valid as facet for the pattern "^[a-zA-z][a-zA-Z0-9]*$" for the type nameType

I can't get why. Using it on RegExr (/^[a-zA-z][a-zA-Z0-9]*$/gm), it works. Am I missing something in the pattern specification?

One last detail. The validation error is given by the marshaller in the JAXB Java framework.

Answer 1

You need to remove ^ and $ as XSD patterns are anchored implicitly and ^ and $ are not used as anchors in these patterns, and fix the typo in the [a-zA-z] character class, it should be [a-zA-Z] if you need to match any ASCII letter (see this related answer, [A-z] does not only match ASCII letters).

Use

<xsd:pattern value="[a-zA-Z][a-zA-Z0-9]*" />

This pattern will actually match the following

• implicitly matches the start of string
• [a-zA-Z] - any ASCII letter
• [a-zA-Z0-9]* - zero or more ASCII letters and/or digits.
• implicitly matches the end of string