Home > Articles > Web Services > XML

Sams Teach Yourself XML in 21 Days

Sep 16, 2005

📄 Contents

␡

⎙ Print

< Back Page 85 of 288 Next >

Recommended Book 

Sams Teach Yourself XML in 21 Days, 3rd Edition

Learn More Buy

Handling Namespaces in Schemas

DTDs weren't built specially to handle namespaces; as you've seen, they really treat namespace prefixes as part of an element name. XML schemas, on the other hand, were supposed to improve on that situation, and to meet that goal, they support a new attribute: targetNamespace.

The targetNamespace attribute can hold the namespace the XML schema is targeted toward—that is, the namespace that the elements in the XML document uses. If you use multiple namespaces in the XML document, an XML validator will know what XML schema to use, based on the schema's target namespace. In other words, a target namespace lets an XML validator know what XML schema to use to check XML elements in that namespace.

You saw an example using the targetNamespace attribute yesterday in the Internet Explorer examples. In the sample XML document, ch06_02.xml, you used the default namespace "http://xmlpowercorp" for all elements:

<?xml version="1.0"?>
<document xmlns="http://xmlpowercorp"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlpowercorp ch06_03.xsd">
    <text>
        Welcome to XML Schemas!
    </text>
</document>

Then, in the XML schema, ch06_03.xsd, you used the targetNamespace attribute to indicate that this XML schema is for elements in the "http://xmlpowercorp" namespace, which means Internet Explorer will use this schema only for elements in that namespace:

<?xml version="1.0"?>
<xsd:schema targetNamespace="http://xmlpowercorp"
xmlns="http://xmlpowercorp"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
attributeFormDefault="qualified" elementFormDefault="qualified">
  <xsd:element name="document">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:element name="text" type="xsd:string" minOccurs="1" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>
</xsd:schema>

Working with namespaces in XML schema gets a little complex because you can use namespaces in different ways in both an XML schema and the XML document you're validating. Also, XML schemas support a number of different options that can be combined in various ways. It is important that you know that XML schemas treat global element declarations differently than local element declarations when it comes to working with namespaces; this is because global elements can be used as document elements, whereas local elements can't.

As you've seen, globally declared elements and attributes are declared at the top level in the XML schema, directly under the <schema> element. All the other elements and attributes declared in an XML schema are locally declared. When you start working with namespaces, XML schemas allow you to specify whether locals need to be qualified (that is, whether they need a namespace prefix) when used in an XML document.

Declaring Locals Without Qualifying Them

How do you declare locals so that they don't need to be qualified? To specify whether elements need to be qualified, you use the elementFormDefault attribute of the <schema> element, and to specify whether attributes need to be qualified, you use the attributeFormDefault attribute of the same element. You can set the elementFormDefault and attributeFormDefault attributes to "qualified" or "unqualified".

The following example makes both local elements and attributes unqualified:

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    elementFormDefault="unqualified"

       attributeFormDefault="unqualified">

Because you're dealing with namespaces now, let's also take a look at a shortcut way of handling the XML schema URI "http://www.w3.org/2001/XMLSchema" in an XML schema. Up to this point, you've been associating the prefix xsd with that namespace in the XML schema, as in this example:

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xsd:annotation>
        <xsd:documentation>
            Mortgage record XML schema.
        </xsd:documentation>
    </xsd:annotation>
        .
        .
        .

However, if you make "http://www.w3.org/2001/XMLSchema" the default namespace in an XML schema (by using an xmlns attribute, not an xmlns:xsd attribute), you don't need to use a prefix for the XML schema elements:

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    elementFormDefault="unqualified"
    attributeFormDefault="unqualified">
    <annotation>

           <documentation>

               Mortgage record XML schema.

           </documentation>

       </annotation>
        .
        .
        .

That can save some time, but you have to be a little careful because now the XML validator will assume that everything's in the "http://www.w3.org/2001/XMLSchema" namespace. That's a problem because when you say, for example, that the <document> element is of the documentType type, the XML validator needs to know where to find the documentType type; it won't find that type defined in the default "http://www.w3.org/2001/XMLSchema" namespace. You can indicate that local types are declared locally by using a new namespace prefix, such as xmp (for XML Power Corp.) in this example:

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    xmlns:xmp="http://xmlpowercorp"
    elementFormDefault="unqualified"
    attributeFormDefault="unqualified">
    <annotation>
        <documentation>
            Mortgage record XML schema.
        </documentation>
    </annotation>
    <element name="document" type="xmp:documentType"/>
    <complexType name="documentType">
        <sequence>
            <element ref="xmp:comment" minOccurs="1"/>
            <element name="mortgagee" type="xmp:recordType"/>

               <element name="mortgages" type="xmp:mortgagesType"/>

               <element name="bank" type="xmp:recordType"/>
        </sequence>
        .
        .
        .

Listing 7.1 shows the entire XML schema ch07_01.xsd.

Example 7.1. An XML Schema That Has Unqualified Locals (`ch07_01.xsd`)

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    xmlns:xmp="http://xmlpowercorp"
    elementFormDefault="unqualified"
    attributeFormDefault="unqualified">
    <annotation>
        <documentation>
            Mortgage record XML schema.
        </documentation>
    </annotation>
    <element name="document" type="xmp:documentType"/>
    <complexType name="documentType">
        <sequence>
            <element ref="xmp:comment" minOccurs="1"/>
            <element name="mortgagee" type="xmp:recordType"/>
            <element name="mortgages" type="xmp:mortgagesType"/>
            <element name="bank" type="xmp:recordType"/>
        </sequence>
        <attribute name="documentDate" type="xmp:date"/>
    </complexType>
    <complexType name="recordType">
        <sequence>
            <element name="name" type="xmp:string"/>
            <element name="location" type="xmp:string"/>
            <element name="city" type="xmp:string"/>
            <element name="state" type="xmp:string"/>
        </sequence>
        <attribute name="phone" type="xmp:string"
            use="optional"/>
    </complexType>
    <complexType name="mortgagesType">
        <sequence>
            <element name="mortgage" minOccurs="0" maxOccurs="8">
                <complexType>
                    <sequence>
                        <element name="property" type="xmp:string"/>
                        <element name="date" type="xmp:date" minOccurs="0"/>
                        <element name="loanAmount" type="xmp:decimal"/>
                        <element name="term">
                        <simpleType>
                            <restriction base="integer">
                                <maxInclusive value="30"/>
                            </restriction>
                        </simpleType>
                        </element>
                    </sequence>
                    <attribute name="loanNumber" type="xmp:loanNumberType"/>
                </complexType>
            </element>
        </sequence>
    </complexType>
    <simpleType name="loanNumberType">
        <restriction base="string">
            <pattern value="\d{2} \d{4} \d{2}"/>
        </restriction>
    </simpleType>
    <element name="comment" type="xmp:string"/>
</schema>

The only two elements that are global in the new XML schema, ch07_01.xsd, are <document> and <comment>, so they're the only ones that need to be qualified with a namespace prefix. Listing 7.2 shows an XML document (ch07_02.xml) that ch07_01.xsd would validate.

Example 7.2. An XML Document That Has Unqualified Locals (`ch07_02.xml`)

<?xml version="1.0" encoding="UTF-8"?>
<xmp:document
    xmlns:xmp="http://xmlpowercorp"
    documentDate="2005-03-02">
    <xmp:comment>Good risk</xmp:comment>
    <mortgagee phone="888.555.1234">
        <name>James Blandings</name>
        <location>1234 299th St</location>
        <city>New York</city>
        <state>NY</state>
    </mortgagee>
    <mortgages>
        <mortgage loanNumber="66 7777 88">
            <property>The Hackett Place</property>
            <date>2005-03-01</date>
            <loanAmount>80000</loanAmount>
            <term>15</term>
        </mortgage>
        <mortgage loanNumber="11 8888 22">
            <property>123 Acorn Drive</property>
            <date>2005-03-01</date>
            <loanAmount>90000</loanAmount>
            <term>15</term>
        </mortgage>
        <mortgage loanNumber="33 4444 11">
            <property>99 West Pocusset St</property>
            <date>2005-03-02</date>
            <loanAmount>100000</loanAmount>
            <term>30</term>
        </mortgage>
        <mortgage loanNumber="55 3333 88">
            <property>19 Johnson Place</property>
            <date>2005-03-02</date>
            <loanAmount>110000</loanAmount>
            <term>30</term>
        </mortgage>
        <mortgage loanNumber="22 6666 99">
            <property>345 Notingham Court</property>
            <date>2005-03-02</date>
            <loanAmount>120000</loanAmount>
            <term>30</term>
        </mortgage>
    </mortgages>
    <bank phone="888.555.8888">
        <name>XML Bank</name>
        <location>12 Schema Place</location>
        <city>New York</city>
        <state>NY</state>
    </bank>
</xmp:document>

Declaring and Qualifying Locals

Despite what we discussed in the preceding section, we can require that locals be qualified with a namespace prefix. For example, we can assign the value "qualified" to the elementFormDefault attribute instead of using "unqualified", as in the XML schema ch07_01.xsd. Here's how you do that:

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    xmlns:xmp="http://xmlpowercorp"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">
        .
        .
        .

Now you have to qualify both locals and globals in the XML document, as shown in ch07_03.xml in Listing 7.3.

Example 7.3. An XML Document That Has Qualified Locals (`ch07_03.xml`)

<?xml version="1.0" encoding="UTF-8"?>
<xmp:document
    xmlns:xmp="http://xmlpowercorp"
    documentDate="2005-03-02">
    <xmp:comment>Good risk</xmp:comment>
    <xmp:mortgagee phone="888.555.1234">
        <xmp:name>James Blandings</xmp:name>

        <xmp:location>1234 299th St</xmp:location>
        <xmp:city>New York</xmp:city>
        <xmp:state>NY</xmp:state>
    </xmp:mortgagee>
    <xmp:mortgages>
        <xmp:mortgage loanNumber="66 7777 88">
            <xmp:property>The Hackett Place</xmp:property>
            <xmp:date>2005-03-01</xmp:date>
            <xmp:loanAmount>80000</xmp:loanAmount>
            <xmp:term>15</xmp:term>
        </xmp:mortgage>
        .
        .
        .
        <xmp:mortgage loanNumber="22 6666 99">
            <xmp:property>345 Notingham Court</xmp:property>
            <xmp:date>2005-03-02</xmp:date>
            <xmp:loanAmount>120000</xmp:loanAmount>
            <xmp:term>30</xmp:term>
        </xmp:mortgage>
    </xmp:mortgages>
    <xmp:bank phone="888.555.8888">
        <xmp:name>XML Bank</name>
        <xmp:location>12 Schema Place</location>
        <xmp:city>New York</xmp:city>
        <xmp:state>NY</xmp:state>
    </xmp:bank>
</xmp:document>

You can also require that attributes be qualified by setting attributeFormDefault to "qualified":

<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://xmlpowercorp"
    xmlns:xmp="http://xmlpowercorp"
    elementFormDefault="qualified"
    attributeFormDefault="qualified">
        .
        .
        .

Now all elements and attributes, both global and local, will have to be qualified. Rather than prefix every element and attribute with xmp:, however, you can make things easier by just putting the entire XML document into the "http://xmlpowercorp" namespace, as shown in Listing 7.4.

Example 7.4. An XML Document That Has Qualified Elements and Attributes (`ch07_04.xml`)

<?xml version="1.0" encoding="UTF-8"?>
<document
    xmlns="http://xmlpowercorp"
    documentDate="2005-03-02">
    <comment>Good risk</comment>
    <mortgagee phone="888.555.1234">
        <name>James Blandings</name>
        <location>1234 299th St</location>
        <city>New York</city>
        <state>NY</state>
    </mortgagee>
    <mortgages>
        <mortgage loanNumber="66 7777 88">
            <property>The Hackett Place</property>
            <date>2005-03-01</date>
            <loanAmount>80000</loanAmount>
            <term>15</term>
        </mortgage>
        .
        .
        .
        <mortgage loanNumber="22 6666 99">
            <property>345 Notingham Court</property>
            <date>2005-03-02</date>
            <loanAmount>120000</loanAmount>
            <term>30</term>
        </mortgage>
    </mortgages>
    <bank phone="888.555.8888">
        <name>XML Bank</name>
        <location>12 Schema Place</location>
        <city>New York</city>
        <state>NY</state>
    </bank>
</document>

Up to this point, you've specified that all locals must be either qualified or unqualified, but there's also a way of working on locals individually: by using the form attribute. For example, in the XML schema ch07_05.xsd, you can leave all locals unqualified except for a single attribute, phone, which must be qualified (see Listing 7.5).

Example 7.5. An XML Schema That Has One Qualified Attribute (`ch07_05.xsd`)

<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="unqualified"
    attributeFormDefault="unqualified">
    <xsd:annotation>
        <xsd:documentation>
            Mortgage record XML schema.
        </xsd:documentation>
    </xsd:annotation>
    <xsd:element name="document" type="documentType"/>
    <xsd:complexType name="documentType">
        .
        .
        .
    </xsd:complexType>
    <xsd:complexType name="recordType">
        <xsd:sequence>
            <xsd:element name="name" type="xsd:string"/>
            <xsd:element name="location" type="xsd:string"/>
            <xsd:element name="city" type="xsd:string"/>
            <xsd:element name="state" type="xsd:string"/>
        </xsd:sequence>
        <xsd:attribute name="phone" type="xsd:string"

               use="optional" form="qualified"/>
    </xsd:complexType>
    <xsd:complexType name="mortgagesType">
        <xsd:sequence>
            <xsd:element name="mortgage" minOccurs="0" maxOccurs="8">
                <xsd:complexType>
                .
                .
                .
                </xsd:complexType>
            </xsd:element>
        </xsd:sequence>
    </xsd:complexType>
    <xsd:simpleType name="loanNumberType">
        <xsd:restriction base="xsd:string">
            <xsd:pattern value="\d{2} \d{4} \d{2}"/>
        </xsd:restriction>
    </xsd:simpleType>
    <xsd:element name="comment" type="xsd:string"/>
</xsd:schema>

Listing 7.6 shows an XML document (ch07_06.xml) that this schema would validate. Note that in this example, all locals are unqualified—except the phone attribute, which is qualified.

Example 7.6. An XML Document That Has One Qualified Attribute (`ch07_06.xml`)

<?xml version="1.0" encoding="UTF-8"?>
<xmp:document
    xmlns:xmp="http://xmlpowercorp"
    documentDate="2005-03-02">
    <xmp:comment>Good risk</xmp:comment>
    <mortgagee xmp:phone="888.555.1234">
        <name>James Blandings</name>
        <location>1234 299th St</location>
        <city>New York</city>
        <state>NY</state>
    </mortgagee>
    <mortgages>
        <mortgage loanNumber="66 7777 88">
            <property>The Hackett Place</property>
            <date>2005-03-01</date>
            <loanAmount>80000</loanAmount>
            <term>15</term>
        </mortgage>
        .
        .
        .
        <mortgage loanNumber="22 6666 99">
            <property>345 Notingham Court</property>
            <date>2005-03-02</date>
            <loanAmount>120000</loanAmount>
            <term>30</term>
        </mortgage>
    </mortgages>
    <bank xmp:phone="888.555.8888">
        <name>XML Bank</name>
        <location>12 Schema Place</location>
        <city>New York</city>
        <state>NY</state>
    </bank>
</xmp:document>

That finishes our discussion on namespaces and XML schemas. The last topic you'll take a look at today is how to annotate XML schemas.

< Back Page 85 of 288 Next >

🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Privacy Notice

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
Such marketing is consistent with applicable law and Pearson's legal obligations.
Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

As required by law.
With the consent of the individual (or their parent, if the individual is a minor)
In response to a subpoena, court order or legal process, to the extent permitted or required by law
To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
To investigate or address actual or suspected fraud or other illegal activities
To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020

Email Address