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XML Schema Exercises

To help you become familiar with the panels available when working with Schema resources, we have included two step-by-step exercises. The first exercise walks you through the creation of a simple schema, introducing you to the fundamental features of the editing environment. The second exercise introduces some more advanced concepts, notably the creation and implementation of complex and simple types. Each example should take about 15-20 minutes to complete.

Exercise 1: Building a Simple Schema

In this example, you will build an XML Schema 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 21 Schema Component

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

To create the project and the manufacturer schema:

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

2.	Drag a Schema icon from the XML Tools palette into the design panel. This creates a Schema resource.

3.	Double click the Schema resource in the design panel.

A series of new panels will appear.

4.	Resize the panels, so that the elements/types panel is prominently displayed.

The elements/types panel presents an inventory of all of the elements and complex types allowed within a document conforming to this schema. The elements/types panel consists of the content model diagram (upper half) and the element/type list (lower half). The element/type 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.

5.	To define the manufacturer root element, follow these steps:

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

Figure 35 Define Root Element

b.	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.

6.	To create the next element, move your cursor to the row below manufacturer and type date.issued.

7.	Now define date.issued as a date using the following steps:

a.	Tab to the Content column.

b.	Click the Content Type button and select “Type” from the drop down menu.

Figure 36 Define Content Type

c.	Tab to the next field. (Notice that the column heading changes from “Content Model” to “Data Type”.) To provide the date.issued element with an appropriate data type, select date from the menu that appears upon clicking Insert.

8.	To specify that the manufacturer element must always include the date.issued element

a.	Move to the Content column on the manufacturer row

b.	Select “Elements” from the Content Type menu. This restricts the content model for manufacturer to elements only.

c.	Tab to the Content Model column and click the insert button.

d.	Select date.issued to restrict the contents of manufacturer to one and only one date.issued element.

You are now ready to create a second element called product.

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

2.	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 indicate 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 sequences. (For more information on sequence indicators 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.

3.	Tab from this field. The Auto Create dialog box appears. Click the Globally defined button, then click Create. (For the purposes of this exercise, all declarations will be global.)

Figure 37 Auto Create Dialog Box

4.	As it is currently defined, all elements are required. At times, you may want an element to be optional. For the purposes of this exercise, make description an optional element:

a.	Go back to the product content model and highlight description.

b.	Once highlighted, click the “optional” button on the tool bar that appears. Notice the '?' that was appended to description.

Figure 38 Adding Optional Element

For more information on occurrence indicators, see Building Content Models: Occurrence and Sequence Indicators.

5.	Make price a decimal data type by clicking on price where it appears in the Element column. Tab over to the Content column and select “Type” from Content Type drop down menu. Tab over to the Data Type column and choose decimal from the Insert menu.

6.	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.

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

To further refine the definitions of these attributes, you can right-click on each of their names and choose “Go to <name>“or click Attributes on the toolbar. The attributes panel will appear with options for data typing the attribute and for indicating its usage (optional, required, default, fixed, or prohibited).

8.	Within the attributes panel, indicate that the values of the start.date and end.date attributes should be of type date.

You can use the navigation buttons on the toolbar or the Schema>View menu to open and close between the editor's panels.

XML schemas typically have a single root element that contains all other elements. In this schema, our root element will be called price.list.

1.	Return to the elements/types panel and add an element named price.list. Press tab and specify “Elements” content.

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

Figure 39 Schema with Complete List of Elements

You have completed creating the schema. In the configuration panel, name the file “pricelist”. You may also want to change the automatically generated target namespace to a URL meaningful to your organization.

Figure 40 Name the File in Configuration Panel

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 elements/ types 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 41.) 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.

The diagram for the price list schema is shown in Figure 41.

Figure 41 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 on the source panel icon 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 exercise. This tutorial introduced the basic steps required to create an XML Schema. Exercise 2: Defining and Deriving Complex and Simple Types will teach you how to create and use your own complex and simple types.

To learn how to build a sample XML document based on the schema you have just built, see XML Instance Exercise.

Exercise 2: Defining and Deriving Complex and Simple Types

In this example, you will build a sample XML Schema for an address. The exercise introduces a modular approach to schema design, as more detailed complex and simple types are derived from more generic ones. Here is a guide to the information you'll be using.

Table 22 Schema Component for an Address

Component	Description
Address	Complex type from which two other complex types are derived
name	Element for the name of the addressee
street	Element for the street address
city	Element for the city
USAdress	Complex type derived by extension from Address
state	Element for the state
zip	Element for the zip code
UKAddress	Complex type derived by extension from Address
postcode	Element for the UK postal code
exportCode	Element for the UK export code
USState	Simple type containing an enumeration

Getting Started

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

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

3.

Within the design panel, double click the schema icon. A series of new panels will appear. Resize the panels, such that the elements/types panel is prominently displayed. The elements/types panel presents an inventory of all of the elements and complex types allowed within a document conforming to this schema. The elements/types panel consists of the content model diagram (upper half) and the element/type list (lower half). The element/type 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.

4.	To create a new complex type, click in the first field of the second row (under column “D”). The field initially displays an “E”, an indication that the row is used for an element declaration. To use the row for a complex type definition, click Decl Type and choose “T” from the menu.

Figure 42 Create a New Complex Type

5.	Tab to the adjacent empty field in the second column, and type in Address as the name of the complex type. Tab to the “Derives From” column. Notice that the second column's heading has changed from “Element” to “Complex Type”.

6.

Later in this exercise you'll use the “Derives From” column to extend the Address complex type. For now, however, we can bypass this field, and tab to the Content field. The content will default to “Elements”, which is the desired content. (Other content types could be selected by way of the menu presented by clicking the Content Type button.)

7.	Tab to the Content Model field. With the pointer positioned between the parentheses, type in the following elements, separated by commas: name, street, city.

Figure 43 Enter Content Model Elements

8.	Tab from the “Content Model” field. The Auto Create dialog box appears. Indicate that the new elements should be Globally defined and then click Create. (For the purposes of this tutorial, all declarations will be global.)

Before you continue to build the address schema, save your progress to this point. In the configuration panel, name your schema “address”. You should also specify a target namespace to differentiate this schema from all others. The Target Namespace field will be pre-populated with a randomly generated namespace. Change this namespace to reflect a URL meaningful to your organization. Finally add a prefix, such as “addr”, to be used to indicate that the components you are defining belong to your namespace. Click Apply.

Figure 44 Name Your Schema

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

Continue building the address schema by defining a simple type named USState.

1.	In the Toolbar, click the Data Types button.

2.	In the first field in the Name column, type USState. Tab to the Base Type column. Click Type and choose string from the drop-down menu.

3.

Tab to the Options column. To define a list of possible values for USState, click the Edit Enums button. The properties panel appears in the lower left of the application window with the Enumeration tab active. In the text box at the top of this tab, enter the value 'AK' (without quotes) and then click Add. Follow the same procedure for the values 'AL' and 'AR'. (Of course, there are more postal abbreviations, but let’s stop here.)

Figure 45 Enumeration Tab

4.	The enumeration is automatically created in the Options column of the data types panel.

Now you can define a complex type named “USAddress”.

1.	On the toolbar, click Elements/Types to return to the elements/types panel (you may also need to choose Schema > View > Properties to clear properties.)

2.	Make sure the bottom row of the element/type list reflects a complex type declaration. (A “T” should appear under the column “D”).

3.	In the adjacent empty field, type USAddress.

4.	Tab to the Derives From column and click Extends. Next, click Select and select Address. Notice that the column heading changes to “Extends”.

Notice also that your selection is inserted in the column with the prefix “e_”. This indicates that the type USAddress is being derived from the base type Address by extension. If you derive from a base type by restriction, you'll see the prefix “r_”.

5.	Tab to the Content column and make sure element content is reflected. (Elements should be pre-selected as the most appropriate model).

6.	Tab to the Content Model column. Inside the parentheses, type state, zip. Tab out of the Content Model column.

7.	In the Auto-Create dialog box that appears, click the Globally defined radio button and then click Create.

8.	In the row for the element state, navigate to the Data Type column. Click Insert user-defined type and select USState from the menu of options

Figure 46 Insert User-defined Data Type.

9.	In the row for the element zip, click in the Data Type column. Click Insert to display a menu of XML Schema data types. Choose “More” on this menu to display a submenu. Choose positiveInteger as the data type for zip.

You are now ready to define some elements on your own.

1.	Define a complex type named UKAddress as an extension of Address. Add the element postcode to the content model and create postcode as a global declaration. Also give UKAddress and attribute called exportCode.

Figure 47 Define Complex Type

2.

For further practice, define a simple type (data type) called UKPostcode and assign it to the postcode element. The new simple type can be an extension or restriction of an existing simple type. For example, to be very precise, you could restrict a string by specifying a regular expression (pattern) that the type must match.

The address types created in this schema could later be applied to elements. For example, shipTo and billTo elements could be added to this schema and be declared as having the type USAddress. These type definitions could also be used in other schemas. As a final exercise, create a new schema resource and import the address schema namespace you created in this tutorial. The easiest way to import a namespace is to use the Add Namespace option of the overview panel, which enables you to browse and select another schema from your project. Once the address schema created in this exercise has been imported, create a shipTo of type USAddress. To references an element, attribute or type existing in another namespace, use the prefix for the external namespace followed by a colon and the component name. Figure 48 shows a new schema referencing the USAddress type created in this schema.

Figure 48 Referencing a Complex Type in Another Schema

Conclusion

This exercise serves as an introduction to XML Schema design. Review the documentation to learn more about XML Schema functionality and to facilitate your implementation of advanced features.

Copyright © TIBCO Software Inc. All Rights Reserved