Validate filled elements but ignore empty elements

Yaneeve was kind enough to fix my schema for me which was causing lots of problems

This isn't so much of a problem but i would be nice to have this work

Some of my elements are empty such as a mobile number or fax number.

I need to validate the length of the element to make sure they have the correct number of digits but i don't want to validate an empty element

cvc-minLength-valid: Value '' with length = '0' is not facet-valid with respect to minLength '11' for type 'mobile'.

cvc-type.3.1.3: The value '' of element 'conmobile' is not valid.

Is there a way i can skip an empty element and validate it only if it is not empty?

My example user in the xml

<member>
    <user id="4">
        <personal>
            <name>Connor Lawson</name>
            <sex>Male</sex>
            <address1>12 Ash Way</address1>
            <address2></address2>
            <city>Swindon</city>
            <county>Wiltshire</county>
            <postcode>SN3  6GS</postcode>
            <telephone>01791928119</telephone>
            <mobile>07338695664</mobile>
            <email>itunestinker@fsmail.co.uk</email>
        </personal>
        <account>
            <username>iTuneStinker</username>
            <password>3a1f5fda21a07bfff20c41272bae7192</password>
            <userlevel>3</userlevel>
            <signupdate>2010-03-26T09:23:50</signupdate>
        </account>
    </user>
    <festival id="1">
        <event>
            <eventname>Oxford Folk Festival</eventname>
            <url>http://www.oxfordfolkfestival.com/</url>
            <datefrom>2010-04-07</datefrom>
            <dateto>2010-04-09</dateto>
            <location>Oxford</location>
            <eventpostcode>OX19BE</eventpostcode>
            <coords>
                <lat>51.735640</lat>
                <lng>-1.276136</lng>
            </coords>
        </event>
        <contact>
            <conname>Stuart Vincent</conname>
            <conaddress1>P.O. Box 642</conaddress1>
            <conaddress2></conaddress2>
            <concity>Oxford</concity>
            <concounty>Bedfordshire</concounty>
            <conpostcode>OX13BY</conpostcode>
            <contelephone>01865 79073</contelephone>
            <conmobile></conmobile>
            <fax></fax>
            <conemail>stewards@oxfordfolkfestival.com</conemail>
        </contact>
    </festival>
</member>

and my new schema

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:simpleType name="postcode">
        <xs:restriction base="xs:string">
            <xs:minLength value="5"/>
            <xs:maxLength value="8"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="telephone">
        <xs:restriction base="xs:string">
            <xs:minLength value="10"/>
            <xs:maxLength value="13"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="mobile">
        <xs:restriction base="xs:string">
            <xs:minLength value="11"/>
            <xs:maxLength value="11"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="password">
        <xs:restriction base="xs:string">
            <xs:minLength value="32"/>
            <xs:maxLength value="32"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="userlevel">
        <xs:restriction base="xs:integer">
            <xs:enumeration value="1"/>
            <xs:enumeration value="2"/>
            <xs:enumeration value="3"/>
            <xs:enumeration value="4"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:simpleType name="county">
        <xs:restriction base="xs:string">
            <xs:enumeration value="Bedfordshire"/>
            <xs:enumeration value="Berkshire"/>
            <xs:enumeration value="Bristol"/>
            <xs:enumeration value="Buckinghamshire"/>
            <xs:enumeration value="Cambridgeshire"/>
            <xs:enumeration value="Cheshire"/>
            <xs:enumeration value="Cleveland"/>
            <xs:enumeration value="Cornwall"/>
            <xs:enumeration value="Cumberland"/>
            <xs:enumeration value="Derbyshire"/>
            <xs:enumeration value="Devon"/>
            <xs:enumeration value="Dorset"/>
            <xs:enumeration value="Durham"/>
            <xs:enumeration value="East Ridings Of Yorkshire"/>
            <xs:enumeration value="Essex"/>
            <xs:enumeration value="Gloucestershire"/>
            <xs:enumeration value="Hampshire"/>
            <xs:enumeration value="Herefordshire"/>
            <xs:enumeration value="Hertfordshire"/>
            <xs:enumeration value="Huntingdonshire"/>
            <xs:enumeration value="Isle Of Man"/>
            <xs:enumeration value="Kent"/>
            <xs:enumeration value="Lancashire"/>
            <xs:enumeration value="Leicestershire"/>
            <xs:enumeration value="Lincolnshire"/>
            <xs:enumeration value="London"/>
            <xs:enumeration value="Middlesex"/>
            &开发者_StackOverflow中文版lt;xs:enumeration value="Norfolk"/>
            <xs:enumeration value="North Yorkshire"/>
            <xs:enumeration value="Northamptonshire"/>
            <xs:enumeration value="Northumberland"/>
            <xs:enumeration value="Nottinghamshire"/>
            <xs:enumeration value="Oxfordshire"/>
            <xs:enumeration value="Rutland"/>
            <xs:enumeration value="Shropshire"/>
            <xs:enumeration value="Somerset"/>
            <xs:enumeration value="South Yorkshire"/>
            <xs:enumeration value="Staffordshire"/>
            <xs:enumeration value="Suffolk"/>
            <xs:enumeration value="Surrey"/>
            <xs:enumeration value="Sussex"/>
            <xs:enumeration value="Tyne and Wear"/>
            <xs:enumeration value="Warwickshire"/>
            <xs:enumeration value="West Yorkshire"/>
            <xs:enumeration value="Westmorland"/>
            <xs:enumeration value="Wiltshire"/>
            <xs:enumeration value="Wirral"/>
            <xs:enumeration value="Worcestershire"/>
            <xs:enumeration value="Yorkshire"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:element name="folktask">
        <xs:complexType>
            <xs:sequence>
                <xs:element minOccurs="0" maxOccurs="unbounded" ref="member"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="member">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="user" minOccurs="0" maxOccurs="unbounded"/>
                <xs:element ref="festival" minOccurs="0" maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="user">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="personal"/>
                <xs:element ref="account"/>
            </xs:sequence>
            <xs:attribute name="id" type="xs:integer"/>
        </xs:complexType>
    </xs:element>
    <xs:element name="personal">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="name"/>
                <xs:element ref="sex"/>
                <xs:element ref="address1"/>
                <xs:element ref="address2"/>
                <xs:element ref="city"/>
                <xs:element ref="county"/>
                <xs:element ref="postcode"/>
                <xs:element ref="telephone"/>
                <xs:element ref="mobile"/>
                <xs:element ref="email"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="name" type="xs:string"/>
    <xs:element name="sex" type="xs:string"/>
    <xs:element name="address1" type="xs:string"/>
    <xs:element name="address2" type="xs:string"/>
    <xs:element name="city" type="xs:string"/>
    <xs:element name="county" type="xs:string"/>
    <xs:element name="postcode" type="postcode"/>
    <xs:element name="telephone" type="telephone"/>
    <xs:element name="mobile" type="mobile"/>
    <xs:element name="email" type="xs:string"/>
    <xs:element name="account">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="username"/>
                <xs:element ref="password"/>
                <xs:element ref="userlevel"/>
                <xs:element ref="signupdate"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="username" type="xs:string"/>
    <xs:element name="password" type="password"/>
    <xs:element name="userlevel" type="userlevel"/>
    <xs:element name="signupdate" type="xs:dateTime"/>
    <xs:element name="festival">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="event"/>
                <xs:element ref="contact"/>
            </xs:sequence>
            <xs:attribute name="id" type="xs:integer" use="optional"/>
        </xs:complexType>
    </xs:element>
    <xs:element name="event">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="eventname"/>
                <xs:element ref="url"/>
                <xs:element ref="datefrom"/>
                <xs:element ref="dateto"/>
                <xs:element ref="location"/>
                <xs:element ref="eventpostcode"/>
                <xs:element ref="coords"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="eventname" type="xs:string"/>
    <xs:element name="url" type="xs:string"/>
    <xs:element name="datefrom" type="xs:date"/>
    <xs:element name="dateto" type="xs:date"/>
    <xs:element name="location" type="xs:string"/>
    <xs:element name="eventpostcode" type="postcode"/>
    <xs:element name="coords">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="lat"/>
                <xs:element ref="lng"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="lat" type="xs:decimal"/>
    <xs:element name="lng" type="xs:decimal"/>
    <xs:element name="contact">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="conname"/>
                <xs:element ref="conaddress1"/>
                <xs:element ref="conaddress2"/>
                <xs:element ref="concity"/>
                <xs:element ref="concounty"/>
                <xs:element ref="conpostcode"/>
                <xs:element ref="contelephone"/>
                <xs:element ref="conmobile"/>
                <xs:element ref="fax"/>
                <xs:element ref="conemail"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="conname" type="xs:string"/>
    <xs:element name="conaddress1" type="xs:string"/>
    <xs:element name="conaddress2" type="xs:string"/>
    <xs:element name="concity" type="xs:string"/>
    <xs:element name="concounty" type="xs:string"/>
    <xs:element name="conpostcode" type="postcode"/>
    <xs:element name="contelephone" type="telephone"/>
    <xs:element name="conmobile" type="mobile"/>
    <xs:element name="fax" type="telephone"/>
    <xs:element name="conemail" type="xs:string"/>
</xs:schema>

I managed to fix it by using < xs:union >

chnaged from this

<xs:simpleType name="telephone">
    <xs:restriction base="xs:string">
        <xs:minLength value="10"/>
        <xs:maxLength value="13"/>
    </xs:restriction>
</xs:simpleType>

to

<xs:simpleType name="telephone">
  <xs:union>
    <xs:simpleType>
      <xs:restriction base="xs:string">
        <xs:minLength value="10"/>
        <xs:maxLength value="13"/>
      </xs:restriction>
    </xs:simpleType>
    <xs:simpleType>
      <xs:restriction base="xs:string">
        <xs:enumeration value=""/>
      </xs:restriction>
    </xs:simpleType>
  </xs:union>
</xs:simpleType>

Did you try pattern restrictions? Something like this:

<xs:simpleType name="telephone">
  <xs:restriction base="xs:string">
    <xs:pattern value="[0-9]{10,13}|.{0}/>
  </xs:restriction>
</xs:simpleType>

Caution: untested with actual XML.