Elements are fundamental building blocks in XML. Element declarations
provide value constraints, and a description that can be used for
validation, as well as establishing constraining relationships between
related elements and attributes, and controlling substitution of elements.
The following instructions were written for the Resource perspective,
but they will also work in many other perspectives.
To add an
element, follow these steps:
- In the Outline view, right-click the content
model you want to
work with and click Add Element.
- In the Properties view, type a new name for the element in the
Name field.
- Specify its type information by clicking the More button
and selecting the appropriate type.
The Set Type dialog lists all built-in and user-defined types currently
available. You can change the Scope of the
list by selecting one of the following options:
- Workspace. Lists all of the
types available in your workspace.
- Enclosing Project. Lists all
of the types available in the project that contains your file.
- (Default) Current Resource.
List all of the types available in your current file.
- (Optional) Select the appropriate value in the
MinOccurs field. This is the number of times the element may appear. If you want the
element to be optional, select 0. Otherwise, select
1.
- (Optional) Select the appropriate value in the MaxOccurs field. This is the maximum number of times the element may appear. You can
select unbounded to indicate there is no maximum number
of occurrences.
-
(Optional) Click the
Other tab. In
this page, you can specify the following various values for the element:
- block. This field determines
whether the element may be replaced by an element derived from it.
- fixed/default. Click the
More button
and
select the Fixed or
Default radio button and specify an
appropriate value. If you select Fixed, the element has
a fixed value, which cannot be changed. If you select Default,
the element has a default value.
- form. Use this field to
indicate if the appearance of this element in an instance of the XML
schema (that is, an XML file associated with the XML schema) must be
qualified by a namespace.
- maxOccurs. This is the minimum
number of times the element can appear in an instance document. You can
specify this option here or in the General page.
- minOccurs. This is the maximum
number of times the element can appear in an instance document. You can
specify this option here or in the General page.
- nillable. Select true
if you do not want the element to be able to have any child elements,
only attributes.
- Click the Attributes tab. You
can use this page to add attributes, attribute references, attributes group
references, and any attributes to your element.
- An attribute associates an attribute name with a specific type
and value. To add an attribute, right-click in the Attributes page, and click Add
Attribute. You can specify the following values for
an attribute
- fixed/default. Click the
More button
and select the
Fixed or Default radio
button and specify an appropriate value. If you select Fixed, the attribute
has a fixed value, which cannot be changed. If you select Default,
the attribute has a default value.
- form. Use this field to indicate if the appearance
of this attribute in an instance of the XML schema must be qualified by a
namespace.
- name. Enter the name of the attribute.
- type. Click the More button
and select the type of the attribute.
- use. This field indicates how an attribute
may be used in an instance document. If you select optional, the attribute
may appear once, but it does not have to. If you select required, the
attribute must appear once. If you select prohibited, the attribute
must not appear. Note: If you selected the Default radio
button, you must select optional in this field, otherwise the default
value will not be valid.
- An attribute reference provides a reference to a global attribute.
To add an attribute reference, right-click in the Attributes page, and click Add
Attribute Ref. A declaration that references a global
attribute enables the referenced attribute to appear in the instance document
in the context of the referencing declaration. The menu option to add
an attribute reference only appears if there are global attributes defined
elsewhere in the document.
- Select the reference, then select the global attribute you want
it to reference from the ref drop down list.
- An attribute group reference provides a reference to an attribute
group. To add an attribute group reference, right-click in the Attributes
page, and click Add Attribute Group Ref. A
declaration that references an attribute group enables the referenced attribute
group to appear in the instance document in the context of the referencing
declaration. The menu option to add an attribute group reference only appears
if there are attribute groups defined elsewhere in the document.
- Select the reference, then select the attribute group you want
it to reference from the ref drop down list.
- An any element enables element content according
to namespaces, and the corresponding any attribute
element enables attributes to appear in elements. To add an any attribute,
right-click in the Attributes page and click Add Any Attribute. You can specify the following values for an any attribute:
- For a namespace value, you can select ##any (this allows
any well-formed XML from any namespace), ##local (this allows any
well-formed XML that is not declared to be in a namespace, ##other (this
allows any well-formed XML that is not from the target namespace of the type
being defined) or ##targetNamespace (which is shorthand for the target
namespace of the type being defined).
- For a processContents value, you can select skip (the
XML processor will not validate the attribute content at all), lax (the
XML processor will validate the attribute content as much as it can), or strict (the
XML processor will validate all the attribute content).
- Click the Documentation tab if you want
to provide any information about this element. The Documentation page
is used for human readable material, such as a description, and the App
Info page can be used to provide information for applications.
You can add a content model to an element, which is the representation
of any data that may be contained inside the element. For more information
about working with content models, refer to the related tasks.