group Element

Organizes content into a group to specify a sequence.

<group
  maxOccurs="{1 | *}" 
  minOccurs="{0 | 1}" 
  order="{one | seq | many}" >

Attributes

maxOccurs

Maximum number of times the group can occur. The following values can be assigned to this attribute:

1	Occurs at most once.
*	Unlimited number of occurrences.

minOccurs

Minimum number of times the group can occur. The following values can be assigned to this attribute:

0	Not required; the group is optional.
1	Must occur at least once.

order

Constraints on the sequence of elements (and other contained groups) within this group. The following values can be assigned to this attribute:

one	Permits only one instance of each element contained in the group. (This corresponds to the | symbol in the DTD.)
seq	Requires the elements in the group to appear in the specified sequence.
many	Permits the elements in the group to appear (or not appear) in any order.

The "seq" setting is needed to specify valid sequences. For example, it can be used to specify when a particular sequence such as "x1,y1" or "x2,y2" is valid but no other possible combinations are valid. The "seq" value serves the same role as parentheses in a DTD.

Element Information

Remarks

The order attribute takes the same values as the order attribute of the ElementType element.

The minOccurs and maxOccurs attributes have the default value "1." A group with neither attribute must appear once and only once in a content model.

Examples

The following example demonstrates the "one" setting:

<ElementType name="z" order="one">
<element type="x">
<element type="y">
</ElementType>

The following represents a legal instance of the schema:

<z>
  <x/> 
  <y></y> 
</z>

The following example demonstrates the "seq" setting:

<ElementType name="x" order="one">
  <group order="seq">
    <element type="x1">
    <element type="y1">
  </group>
  <group order="seq">
    <element type="x2">
    <element type="y2">
  </group>
</ElementType>

The following two examples represent legal instances of this schema:

<x>
  <x1/> 
  <y1/>
</x>

and:

<x>
  <x2/>
  <y2/>
</x>

The following example demonstrates the "many" setting:

<ElementType name="x" content="eltOnly" order="many">
  <element type="q">
  <element type="r">
</ElementType>

The following five examples represent all legal instances for this schema:

<x> </x>
<x> <q> </x>
<x> <r> </x>
<x> <q> <r> </x>
<x> <r> <q> </x>