How to make an element in XML schema optional?

Question

So I got this XML schema:

<?xml version="1.0"?> <xs:schema version="1.0"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified">
    <xs:element name="request">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="amenity">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="description" type="xs:string" />
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element> </xs:schema>

How do I make the description element optional? So both XML with the description element and without will validate against the XSD.

See also [***XML Schema minOccurs / maxOccurs default values***](https://stackoverflow.com/q/4821477/290085) — kjhughes, Aug 03 '20 at 15:09

score 225 · Accepted Answer · answered Feb 11 '12 at 20:28

225

Try this

<xs:element name="description" type="xs:string" minOccurs="0" maxOccurs="1" />

if you want 0 or 1 "description" elements, Or

<xs:element name="description" type="xs:string" minOccurs="0" maxOccurs="unbounded" />

if you want 0 to infinity number of "description" elements.

answered Feb 11 '12 at 20:28

Dmitry Kudryavtsev

16,354
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6

You beat me to the answer, but here's a useful link: http://www.w3.org/TR/xmlschema-0/#OccurrenceConstraints – kdgregory Feb 11 '12 at 20:30
8

`maxOccurs` defaults to `1`, so your top example doesn't need to specify it. – Duncan Jones Aug 11 '16 at 07:19
1

Indeed, tested it, and you only need to specify minOccurs="0" to make it optional if you want to allow one element max. – Wouter Schut Jan 10 '17 at 08:42
maxOccurs defaulting to 1 - very useful info, thank you. – thonnor Jan 20 '17 at 23:56
Thank you! This [link](https://www.w3schools.com/xml/schema_complex_indicators.asp) contains others informations – cavalsilva Jan 18 '19 at 17:12

score 24 · Answer 2 · edited Jun 08 '17 at 13:14

Set the minOccurs attribute to 0 in the schema like so:

<?xml version="1.0"?>
  <xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:element name="request">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="amenity">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="description" type="xs:string" minOccurs="0" />
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element> </xs:schema>

How to make an element in XML schema optional?

2 Answers2

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