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DTD Exercise

To help you become familiar with the panels available when working with DTD resources, we have included this step-by-step exercise. The exercise walks you through the creation of a simple schema, introducing you to the fundamental features of the editing environment. The exercise should take about 10-15 minutes to complete.

In this example, you will build a DTD for a price list. A document conforming to this schema could be used by a reseller to define the format in which product information is received from manufacturers. Here is a guide to the information we'll be using:

Table 38 Schema Elements

Component	Description
price.list	the “root” element inside of which all others will appear
manufacturer	a container for information about a manufacturer
name	the name of the manufacturer
date.issued	the date the price list was issued
product	a container for information about a product
sku	the product's sku (Stock Keeping Unit - Inventory Identifier)
product.name	the product's name
price	the product's price
description	a text description of the product
promotion	a container for information about a price promotion
start.date	the date the promotion starts
end.date	the date the promotion ends

Getting Started

1.	In the project panel, create a project folder named QuickTour.

2.	To create a new DTD resource, drag the DTD icon from the XML Tools palette and drop into the design panel.

3.	Within the design panel, double click the DTD icon.

4.

A new set of panels will appear. Resize the panels, such that the elements panel is prominently displayed. The elements panel presents an inventory of all of the elements and complex types allowed within a document conforming to this schema. The elements panel consists of the content model diagram (upper half) and the element list (lower half). The element list, where most of the work in this exercise will be performed, has a tabular format, with the fields in each row identified by column headings.

Figure 70 Add Attribute

Now you are ready to build the schema.

5.	In the Element column, select root and replace it with manufacturer.

6.	Tab across to the Attributes column and type in name. Here you can define attributes for an element. When entering multiple attributes, commas should separate them.

You can navigate around the tables in each panel by using ENTER, TAB, SHIFT-ENTER, and SHIFT-TAB.

7.	To create the next element, move your cursor to the row below manufacturer and type date.issued. Tab to the Content column and select “Text” by clicking on the Content Type button and selecting “Text” from the drop down menu.

Now, go back and specify a content model for manufacturer to ensure that the manufacturer element always includes the date.issued element.

8.	Move to the Content column on the manufacturer row and select “Elements” from the Content Type menu. This restricts the content model for manufacturer to elements only.

9.	Tab to the Content Model column and position the cursor inside the parentheses “()” which are automatically created when editing an element's content model.

10.	Type date.issued into the Content Model column to restrict the contents of manufacturer to one and only one date.issued element. Since name is an attribute, it does not need to be within the manufacturer element.

Figure 71 Add Element

11.	Move to the empty line below date.issued and type product then press tab. Select “Elements” from the Content Type menu and press tab.

12.	Move to the content model column for product, position your cursor inside the “()” and type sku, product.name, price, description, promotion

The commas between elements are indicative of a Sequence (this followed by this followed by this). Elements may also represent a Choice (this or this or this). Choice uses a “|” rather than a “,” between element names. In the Content Model column, groups of elements can be EITHER choices or sequence. For more information, see Building Content Models: Occurrence and Sequence Indicators.

When adding elements to a content model (within the “Content Model” column), if your input exceeds the column width, type Ctrl+E or select “Expand” from the Schema>View menu to open a larger window for editing the selected area.

13.	Tab from this field and select “Create” (fig 1.4) when prompted. Notice that new Elements are created for you and added to the list. By default, new elements are automatically created with text only content

Figure 72 Auto Create Dialog Box

.

As it is currently defined, all elements are required. In some instances, you may want an element to be optional. For the purposes of this exercise, description will be made an optional element.

14.	Go back to the product content model and highlight description. Once highlighted, click the “optional” button on the tool bar that appears. Notice the '?' that was appended to description.

Elements can be defined as either required OR optional. They may also be defined as repeatable by clicking on the Repeatable button in the Content Model toolbar. For more information, see Building Content Models: Occurrence and Sequence Indicators.

15.	A promotion is a discounted price over some period of time. This will be represented using a combination of elements and attributes. Make a content model for promotion by specifying “Elements” in the Content column and then entering price into the Content Model column.

16.	Tab to the Attributes column for promotion and enter start.date, end.date. Press Tab.

17.	XML schemas typically have a single root element that contains all other elements. In this instance, our root element will be called price.list. Below promotion, type in price.list, press tab, and specify “Elements” content.

18.	Enter manufacturer, product+ as the content model. (The plus sign designates the product element as required and repeatable.) Tab out of the field to update the schema.

Figure 73 Schema Elements

You have completed creating the schema. In the configuration panel, name the file “pricelist” and click Apply to save your work.

The Apply button makes the file available to other resources in the project. The schema is saved when the entire project has been saved.

Reviewing the Schema

Graphical view

By defining content models, a structure for the document is established. This structure can be thought of as a tree where the root is the encompassing element and its branches are the elements and attributes that may be contained within it (as defined by the content model). In turn each branch may have branches defined by their content model. The diagram at the top of the element panel provides a graphical view of these relationships. Explore the content model by clicking on the elements to expand and collapse their content. (Specifically, click on the Element Content Indicator icon, labeled in Figure 74.) Note that only elements that define a content model can be expanded. Within the diagram, double clicking on the root element, in this case price.list, will produce a graphical view of the entire schema, shown in Figure 74.

Figure 74 Graphical View of the Schema

For each element and attribute in the diagram, a right button menu offering key editing functions is provided. Right-click the background to zoom in or out of the diagram as a whole.

Source view

To view the actual schema syntax for the schema you've created, open the source panel by clicking Source on the main toolbar. The notes panel, which allows you to enter supplemental information about any element or attribute, also allows you to view the source for individual declarations. Open the notes panel using the Schema menu (Schema > View > Notes). Click on the “Source Preview” tab at the bottom of the notes panel to view the source for the element declaration currently selected in the element list.

Conclusion

You have completed the DTD Quick Tour. Notice that the elements and attributes were not constrained by data typing beyond text, because types such as integer, decimal and date are not available in a DTD. To see how these types could be implemented in a price list schema, see XML Schema Exercises

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