How to Extend a XSD Restriction/Pattern Value - xsd

Question

I am trying to restrict the values for two Elements that can share (most of) the same attribute 'type' values. I'd like to be able to extend those values for one of the Elements (see sample code below -- the 'End' element's 'Value' attribute can have the same entries as the 'Start' element's 'Value' attribute, but there can be additional values). I don't think my solution in the example is correct; is there a simple solution that I can follow?
<xsd:simpleType name="StartAndEndTypeType">
<xsd:restriction base="xsd:string">
<xsd:pattern value="(value1|value2|value3"/>
</xsd:restriction>
</xsd:simpleType>
<xs:element name="Start">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="StartAndEndTypeType"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="End">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="StartAndEndTypeType|value4"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>

Answer 1

This can be done in a number of ways.
Note I've changed your pattern facet to an enumeration as it works better for the example (but a pattern facet could be put back if required)
1 - Restricting a type
The StartAndEndTypeType contains all the values required, and then you restrict the ones you don't want in the StartType.
<?xml version="1.0" encoding="utf-8" ?>
<!--Created with Liquid Studio 2019 BETA (https://www.liquid-technologies.com)-->
<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:simpleType name="StartAndEndTypeType">
<xs:restriction base="xs:string">
<xs:enumeration value="value1" />
<xs:enumeration value="value2" />
<xs:enumeration value="value3" />
<xs:enumeration value="value4" />
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="StartType">
<xs:restriction base="StartAndEndTypeType">
<xs:enumeration value="value1" />
<xs:enumeration value="value2" />
<xs:enumeration value="value3" />
</xs:restriction>
</xs:simpleType>
<xs:element name="Start">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="StartType" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="End">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="StartAndEndTypeType" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>
2 - Extend the base definition using a union
You define the base type StartAndEndTypeType, then add to it the additional values you want to allow using an xs:union.
<?xml version="1.0" encoding="utf-8" ?>
<!--Created with Liquid Studio 2019 BETA (https://www.liquid-technologies.com)-->
<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:simpleType name="StartAndEndTypeType">
<xs:restriction base="xs:string">
<xs:enumeration value="value1" />
<xs:enumeration value="value2" />
<xs:enumeration value="value3" />
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="EndType">
<xs:union memberTypes="StartAndEndTypeType">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="value4" />
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
<xs:element name="Start">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="StartAndEndTypeType" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="End">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:float">
<xs:attribute name="Value" type="EndType" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>