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Defining Groups of Elements and Attributes in XML Schemas

The XML Schema Recommendation allows you to specify groups of elements and groups of attributes. Here is an example of an element group, purchaseType: 

 <xsd:group name="purchaseType">
               
     <xsd:choice>
               
         <xsd:element name="retail"/>
               
         <xsd:element name="internet"/>
               
         <xsd:element name="mailOrder"/>
               
     </xsd:choice>
               
 </xsd:group>

Specification of a group makes it easier to update the schema. You only need to update the group definition. There is no need to change the references to the group.

Here is an example of an attributeGroup, deliveryDetail. 

 <xsd:attributeGroup name="deliveryDetail">
               
     <xsd:attribute name="method"/>
               
     <xsd:attribute name="vendor"/>
               
     <xsd:attribute name="dateShipped"/>
               
     <xsd:attribute name="dateArrived"/>
               
 </xsd:attributeGroup>

This section discusses the following topics:

Defining Groups of Elements in XML Schemas - Diagram View

To define a group of elements:
1. Define the elements that you want to be in the group. See Defining Elements and Attributes in XML Schemas.
2. Right-click the schema node .
3. In the shortcut menu, select Add > Group.

Alternatives: This operation is also available from the XMLSchema > Diagram > Add > Group menu and from the Add button .

The new group is added to the XML Schema. It is displayed in the diagram and in the text pane (if you have it open). The properties for the new group are displayed in the Properties window.

4. Specify the group name in the Name property in the Properties window.
5. Right-click the new group.
6. In the shortcut menu, select Add > and then select the modifier for the group of elements - All, Choice, or Sequence. In the Properties window, click the fields for the Min Occur. and Max Occur. properties to specify their values. These properties determine how often the group of the elements with the selected modifier can appear.
7. Drag the elements defined in step 1 and drop them on the all, choice, or sequence modifier created in step 6.

Alternative

If you prefer, you can create the element group first, define the modifier for the group elements, and then add new elements to the group by right-clicking on the modifier and selecting Add > Element. If you do this, you must then define each of the elements you added to the group.

Defining Groups of Elements in XML Schemas - Tree View

To define a group of elements:
1. Define the elements that you want to be in the group. See Defining Elements and Attributes in XML Schemas.
2. Click the Schema node.
3. In the left tool bar, click New Group . In the Tree view, Stylus Studio displays a field for the new group.
4. Type a name for the group of elements and press Enter.
5. In the left tool bar, click New Model Group . Stylus Studio displays a pop-up menu that lists the model group modifiers. See Model Group Properties in XML Schemas.
6. Double-click a modifier that applies to at least one element that will be in the group.
7. In the Properties window, double-click the fields for the Min Occur. and Max Occur. properties to specify their values. These properties determine how often the subgroup of the elements with the selected modifier can appear.
8. For each element that you want to apply the selected modifier to, perform these steps:
a. Click New Reference to Element . Stylus Studio displays a pop-up menu that lists the elements defined in the schema.
b. Double-click the element you want to add to the group.
c. Click the modifier to add another element reference.
9. To add more elements to the group and specify a different modifier for them, click the name of the group in the Tree view, and repeat step 5 through step 8.

In any location where you can add a model group, you can also add a reference to a model group definition.

Defining attributeGroups in XML Schemas - Diagram View

You define attributeGroups in much the same way that you define element groups - by creating the attributes you want to add to the attributeGroup, creating the attributeGroup, and then dragging-and-dropping the attributes in the attributeGroup. As with element groups, you can define the attributeGroup first and then add new attributes to it, if you prefer. The following procedure describes how to create an attributeGroup by creating the attributes at the same time you create the attributeGroup.

To define an attributeGroup:
1. Right-click the schema node .
2. In the shortcut menu, select Add > AttributeGroup.

Alternatives: This operation is also available from the XMLSchema > Diagram > Add > AttributeGroup menu and from the Add button .

The new attributeGroup is added to the XML Schema. It is displayed in the diagram and in the text pane (if you have it open). The properties for the new attributeGroup are displayed in the Properties window.

3. Right-click the new attributeGroup.
4. In the shortcut menu that appears, select Add > Attribute.

The new attribute is added to the attributeGroup.

Figure 257. attributeGroup with New Attribute

5. Make sure the new attribute is selected. In the Properties window, click the Data Type field.
6. Enter or select the type of the attribute.
7. Repeat step 3 through step 6 for each attribute that you want to be in the group.

Defining attributeGroups in XML Schemas - Tree View

To define an attributeGroup:
1. Click the Schema node.
2. In the left tool bar, click New Attribute Group . In the Tree view, Stylus Studio displays a field for the new attributeGroup.
3. Type a name for the attributeGroup and press Enter.
4. In the left tool bar, click New Attribute Definition . In the Tree view, Stylus Studio displays a field for the new attribute definition.
5. Type a name for the new attribute and press Enter. Stylus Studio displays a scrollable, pop-up menu that lists the built-in simpleTypes and any previously defined simpleTypes.
6. Double-click the type of the new attribute.
7. For each additional attribute you want to add to the group, click the name of the attributeGroup in the Tree view, and repeat step 4 through step 6.
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