XSD: Options for allowing null values when declaring xs:integer data types

Question

My problem (or question) centers around empty elements which are typed as xs:integer. I need to allow for empty elements so I used a union to allow an empty element or a valid integer as the value as shown in the schema below. However, my schema serves a dual role and also needs to be imported into 3rd party software which expects data types of String, Float, Integer or Date. If I code the schema using the union method for all integers they will not be typed as integers in the software. Is there another way other than the union method of allowing an empty element for integer data types? I'd like to just have the one XSD but can have two if that is what needs to happen.

Given XML sample of:

<?xml version="1.0" encoding="UTF-8"?>
<company>
    <division>
        <department>
            <roles/>
            <employees>7</employees>
        </department>
    </division>
</company>

And schema of:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified">
    <xs:simpleType name="nullval">
        <xs:union memberTypes="IntegerType empty"/>
    </xs:simpleType>
    <xs:simpleType name="IntegerType">
        <xs:restriction base="xs:integer"/>
    </xs:simpleType>
    <xs:simpleType name="empty">
        <xs:restriction base="xs:string">
            <xs:maxLength value="0"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:element name="company">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="division">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="department" minOccurs="0" maxOccurs="unbounded">
                                <xs:complexType>
                                    <!-- elements may appear in any order -->
                                    <xs:all minOccurs="0" maxOccurs="1">
                                        <xs:element name="roles" type="nullval"/>
                                        <xs:element name="employees" type="xs:integer"/>
                                    </xs:all>
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

Answer 1

Have you tried

<xs:element name="roles" type="xs:integer" nillable="true"/>

Answer 2

What you have to do is to assign two restrictions on the same element, plus make a union of them such as in the following example:

<xs:element name='job_code'>
  <xs:simpleType>
    <xs:union>
      <xs:simpleType>
        <xs:restriction base='xs:string'>
          <xs:length value='0'/>
        </xs:restriction>
      </xs:simpleType>
      <xs:simpleType>
        <xs:restriction base='xs:integer'>
        </xs:restriction>
      </xs:simpleType>
    </xs:union>
  </xs:simpleType>
</xs:element>

Using this restriction, you tell the XML validation to allow any integer value and allowing the element if it is empty.