Constraining Facets on List Datatypes

XSD Tutorials - Herong's Tutorial Examples

∟"simpleType" - Defining Your Own Simple Datatypes

∟Constraining Facets on List Datatypes

This section describes fundamental and constraining facets on list datatypes: 'length', 'minLength', 'maxLength', 'pattern', 'enumeration' and 'assertions'. New simple datatype can be defined with a 'restriction' component using a list datatype as the base.

From the previous tutorial, we know that a list datatype is defined as a datatype where the entire lexical representation is mapped to a list of items separated by whitespaces. And its item datatype is another atomic datatype or atomic union datatype. Now let's see what facets are supported on list datatypes.

A list construction supports 2 groups of facets: fundamental facets and constraining facets:

A list datatype has the following settings for its fundamental facets defined:

    ordered = false
    bounded = false
    cardinality = countably infinite
    numeric = false

A list datatype supports the following constraining facets:

    whiteSpace = collapse
    length = undefined
    minLength = 1
    maxLength = undefined
    pattern = undefined
    enumeration = undefined
    assertions = undefined

That means we can define a new simple datatype with a "restriction" construction component using a list datatype as the base. Some notes on how constraining facets are applied on list values:

"length", "minLength" and "maxLength" are applied on the number of items in the list, not number of characters on any single item.
"pattern" is applied on the entire list, not on each item.
"enumeration" is provides an acceptable list of values.

For example, the following XSD document uses "restriction" components on list datatypes to define 2 new simple datatypes:

<?xml version="1.1"?>
<!-- list_facet_test.xsd
 - Copyright (c) 2002-2013 HerongYang.com. All Rights Reserved.
-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:simpleType name="strList">
  <xs:list itemType="xs:string"/>
</xs:simpleType>

<xs:simpleType name="intList">
  <xs:list>
    <xs:simpleType>
      <xs:restriction base="xs:unsignedByte">
        <xs:minInclusive value="1"/>
        <xs:maxInclusive value="49"/>
      </xs:restriction>
    </xs:simpleType>
  </xs:list>
</xs:simpleType>

<xs:element name="List_Facet_Test">
  <xs:complexType>
    <xs:sequence>

      <xs:element name="Winners" maxOccurs="unbounded">
        <!-- "restriction" on "list" datatype -->
        <xs:simpleType>
          <xs:restriction base="strList">
            <xs:length value="3"/>
            <xs:pattern value="\w{6} \w{5} \w{4}"/>
          </xs:restriction>
        </xs:simpleType>
      </xs:element>

      <xs:element name="WinningNumbers" maxOccurs="unbounded">
        <!-- "restriction" on "list" datatype -->
        <xs:simpleType>
          <xs:restriction base="intList">
            <xs:length value="6"/>
          </xs:restriction>
        </xs:simpleType>
      </xs:element>

    </xs:sequence>
  </xs:complexType>
</xs:element>
</xs:schema>

Here is a sample XML document to test the above XSD document:

<?xml version="1.1"?>
<!-- list_facet_test.xml
 - Copyright (c) 2002-2013 HerongYang.com. All Rights Reserved.
-->
<List_Facet_Test>

   <!-- Valid "Winners" list of 3 items -->
   <Winners>  Herong Maria Bill  </Winners>

   <!-- Invalid "Winners" values -->
   <Winners>  Lee    Maria     Bill </Winners>
   <Winners>  <![CDATA[B. Lee]]> Maria Bill </Winners>

   <!-- Valid "WinningNumbers" list values -->
   <WinningNumbers>  1 20 24 33 37 43  </WinningNumbers>

   <!-- Invalid "WinningNumbers" values -->
   <WinningNumbers>  1 20 24 33 37 43     49 </WinningNumbers>
</List_Facet_Test>

When validating this XML document with my XsdSchemaValidator.java program presented earlier in the book, I get these errors:

herong> java XsdSchemaValidator
^^^ list_facet_test.xsd list_facet_test.xml

Error:
   Line number: 11
   Column number: 47
   Message: cvc-pattern-valid: Value 'Lee Maria Bill' is not facet-
   valid with respect to pattern '\w{6} \w{5} \w{4}' for type
   '#AnonType_WinnersList_Facet_Test'.
   (6 characters are needed on the first item)

Error:
   Line number: 11
   Column number: 47
   Message: cvc-type.3.1.3: The value 'Lee Maria Bill' of element
   'Winners' is not valid.

Error:
   Line number: 12
   Column number: 55
   Message: cvc-pattern-valid: Value 'B. Lee Maria Bill' is not facet-
   valid with respect to pattern '\w{6} \w{5} \w{4}' for type
   '#AnonType_WinnersList_Facet_Test'.
   (CDATA block is not able to "glue" togeter "B. Lee" as 1 item)

Error:
   Line number: 12
   Column number: 55
   Message: cvc-type.3.1.3: The value 'B. Lee Maria Bill' of element
   'Winners' is not valid.

Error:
   Line number: 18
   Column number: 63
   Message: cvc-length-valid: Value '1 20 24 33 37 43 49' with length
   = '7' is not facet-valid with respect to length '6' for type
   '#AnonType_WinningNumbersList_Facet_Test'.
   (only 6 items are allowed)

Error:
   Line number: 18
   Column number: 63
   Message: cvc-type.3.1.3: The value '1 20 24 33 37 43 49' of element
   'WinningNumbers' is not valid.

Failed with errors: 6