xsd select multiple values from enumeration or equivalent type

Question

I have the following XSD sample

Answer 1

If you can loose the comma (not supported as a separator in XSD), and be content with whitespaces, then this is your solution:

<?xml version="1.0" encoding="utf-8" ?>
<!-- XML Schema generated by QTAssistant/XSD Module (http://www.paschidev.com) -->
<xsd:schema elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xsd:element name="days">
        <xsd:simpleType>
            <xsd:list>
                <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                        <xsd:enumeration value="Monday"/>
                        <xsd:enumeration value="Tuesday"/>
                        <xsd:enumeration value="Wednesday"/>
                        <xsd:enumeration value="Thursday"/>
                        <xsd:enumeration value="Friday"/>
                        <xsd:enumeration value="Saturday"/>
                        <xsd:enumeration value="Sunday"/>
                    </xsd:restriction>                  
                </xsd:simpleType>               
            </xsd:list>
        </xsd:simpleType>
    </xsd:element>
</xsd:schema>

You're basically using a list, therefore something like this would be perfectly valid:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<!-- Sample XML generated by QTAssistant (http://www.paschidev.com) -->
<days xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Monday Tuesday Wednesday </days>

To be proactive here... if, for example, one might want to ensure uniqueness of the values, then this cannot be enforced in XSD.

Answer 2

Seems like your use case is better handled with the use of Regular Expressions since you mentioned user input:

.*day(,.*day)*

You can replace *.day with (Monday|Tuesday|...).

Answer 3

as stated above but to show explicitly:

<xs:simpleType name="DayOfWeek">
  <xs:restriction base="xs:string">
    <xs:pattern value="(Mon|Tues|Wed)(,(Mon|Tues|Wed))*"/>
  </xs:restriction>
</xs:simpleType>

This expression includes the values you want plus This also allows "Mon,Mon,Mon,Tues,Mon" which may not be a big problem depending on how you use the data after you read it. I mean if they are flags then: Mon, Mon, Mon isn't a problem.