Specifying That an Element Can Contain One or More Elements in DTDs

Often, you want an element to contain a sequence of elements. Some of these elements might be required, some might be optional, and some might be able to occur more than once. There might even be a group of elements in which only one can appear.

In the Tree tab, to define an element that contains a sequence of elements:

1. Define the elements that you want your new element to contain. See Defining Elements in DTDs.

2. Define the element that contains the sequence of elements. This is the container element.

3. Click the container element name.

4. In the left tool bar, click New Modifier

. Stylus Studio displays a drop-down menu.

5. Double-click Sequence.

6. To add required elements to the container element, click New Reference to Element

in the left tool bar and enter the name of the required element. Do this for each required element. You can change the order later.

At this point, you can add

Optional elements

Elements that can appear one or more times

Elements that can appear zero, one, or more times

Elements that belong to a group in which only one element in the group can be present

The procedure is the same for these modifiers. The only difference is the modifier you select. For example, following are the instructions for adding optional elements:

1. In the DTD editor, click the Sequence modifier.

2. In the left tool bar, click New Modifier.

3. Double-click Optional.

4. For each optional element, click New Reference to Element and enter the name of the optional element. This works only if you want all optional elements to be consecutive. If you want optional elements to be interspersed with required elements or elements that can appear one or more times, you must perform steps 1 through 4 for each element.

In an instance document, the contained elements must appear in the order in which they are specified in the DTD.