<?xml version='1.0' ?>

<students>

  <student>
    <name>
      <first>John</first>
      <middle>Michael</middle>
      <last>Green</last>
    </name>
    <birth_date>
      <month>8</month>
      <day>28</day>
      <year>1992</year>
    </birth_date>
    <sex>male</sex>
    <grade>3</grade>
  </student>

  <student>
    <name>
      <first>Jane</first>
      <middle>Marie</middle>
      <last>Boyd</last>
    </name>
    <birth_date>
      <month>2</month>
      <day>26</day>
      <year>1993</year>
    </birth_date>
    <sex>female</sex>
    <grade>2</grade>
  </student>
  
  <student>
    <name>
      <first>Nancy</first>
      <middle>Elizabeth</middle>
      <last>Butterworth</last>
    </name>
    <birth_date>
      <month>4</month>
      <day>05</day>
      <year>1993</year>
    </birth_date>
    <sex>female</sex>
    <grade>2</grade>
  </student>
    
</students>

• The line that says <?xml version='1.0' ?> tells computer programs and humans that are reading the file that it is an XML file and that the XML code in the file conforms to Version 1.0 of the XML Specification.
  
  
• The portion of the XML code that contains data begins with <students> and ends with </students>. You can assume that the file contains information about (duh!) students!
  
  
• The code is sectioned off into areas that begin with <student> and end with </student>. Each of these sections gives information about a particular student.
  
  
• For each student, each individual tidbit of information is enclosed within a set of labels. For example, the student's grade is preceded by <grade> and followed by </grade>.

• Words are separated from each other by spaces.
• Words are contained in sentences.
• A sentence begins with a capitalized word
• A sentence ends with a period, question mark, or exclamation point.

• Each piece of information starts and ends with a label.
  
  
• Each label starts with < and ends with >.
  
  
• The label that precedes a piece of information does not begin with a slash ("/"); the label that follows a piece of information does begin with a slash.
  
  
• Small pieces of information are contained within larger pieces of information.

<?xml version='1.0' ?>

<faculty_members>

  <faculty_member>
    <name>
      <first>Joanne</first>
      <middle>Gayle</middle>
      <last>Jones</last>
    </name>
    <date_of_birth>08/28/1955</date_of_birth>
    <gender>female</gender>
    <job_title>teacher</job_title>
    <salary>42,000</salary>
  </faculty_member>
  
  <faculty_member>
    <name>
      <first>Ruth</first>
      <middle>Ann</middle>
      <last>Green</last>
    </name>
    <date_of_birth>08/25/1978</date_of_birth>
    <gender>female</gender>
    <job_title>teacher's assistant</job_title>
    <salary>21,500</salary>
  </faculty_member>  
  
  <faculty_member>
    <name>
      <first>Vincent</first>
      <middle>John</middle>
      <last>Pellio</last>
    </name>
    <date_of_birth>07/16/1959</date_of_birth>
    <gender>male</gender>
    <job_title>teacher</job_title>
    <salary>36,500</salary>
  </faculty_member>    
  
</faculty_members>

• First, the two languages use different terminology for the same types of information. For example, the "students" language has tags called "birth_date" and "sex," but the "faculty_members" language uses tags called "date_of_birth" and "gender" to express the same concepts.
  
  
• Second, the information is organized differently in the two languages. In the "students" language, the date of birth is broken down into three pieces: month, day, and year. In the "faculty_members" language, however, the date of birth is expressed as one piece of text.

The words themselves are different:

• Here are some English words:
  
      house hello bicycle dove
  
  
• Here are the Spanish equivalents:
  
      casa ola bicicleta paloma
  
  

The rules of grammar are different:

• In English, an adjective comes before the noun that it modifies:
  
      a white dove
  
  
• In Spanish. an adjective comes after the noun that it modifies:
  
      una paloma blanca
  
  

• XML is not a language. It is a set of rules that specify how to create a language.
• XML's rules specify the syntax that is used for all XML-based languages.
• XML tags specify the meaning of each individual chunk of information.
• XML tags can be nested to describe hierarchical relationships among chunks of information.

1. The Document Type Definition (DTD)
2. The XML Schema

<!ELEMENT faculty_members
  (faculty_member+)>
<!ELEMENT faculty_member
  (name, date_of_birth, gender, job_title, salary)>
<!ELEMENT name
  (first, middle, last)>
<!ELEMENT date_of_birth
  (#PCDATA)>
<!ELEMENT gender
  (#PCDATA)>
<!ELEMENT job_title 
  (#PCDATA)>
<!ELEMENT salary 
  (#PCDATA)>
<!ELEMENT first 
  (#PCDATA)>
<!ELEMENT middle 
  (#PCDATA)>
<!ELEMENT last 
  (#PCDATA)>

<?xml version = "1.0" ?>

<Name>
  <First>Sally</First>
  <Middle>Jessy</Middle>
  <Last>Raphael</Last>
</Name>

<?xml version = "1.0" ?>

<Name>
  <First>Sally</First>
  <Middle>Jessy</Middle
  <Last>Raphael</Last>
</Name>

<?xml version = "1.0" ?>

<faculty_members>

  <faculty_member>
    <name>
      <first>Ronald</first>
      <middle>George</middle>
      <last>Cutler</last>
    </name>
    <date_of_birth>May 17, 1954</date_of_birth>
    <gender>male</gender>
    <job_title>teacher</job_title>
    <salary>45,700</salary>
  </faculty_member>
  
  <faculty_member>
    <name>
      <first>Frederick</first>
      <middle>James</middle>
      <last>Adler</last>
    </name>
    <date_of_birth>March 6, 1958</date_of_birth>
    <gender>male</gender>
    <job_title>teacher</job_title>
    <salary>46,250</salary>
  </faculty_member>  
  
  <faculty_member>
    <name>
      <first>Vivian</first>
      <middle>Arlene</middle>
      <last>Sullivan</last>
    </name>
    <date_of_birth>September 12, 1959</date_of_birth>
    <gender>female</gender>
    <job_title>teacher's assistant</job_title>
    <salary>22,500</salary>
  </faculty_member>    

<faculty_members> 

<?xml version = "1.0" ?>

<faculty_members>

  <faculty_member>
    <name>
      <first>Ronald</first>
      <middle>George</middle>
      <last>Cutler</last>
    </name>
    <date_of_birth>May 17, 1954</date_of_birth>
    <gender>male</gender>
    <salary>45,700</salary>
  </faculty_member>
  
  <faculty_member>
    <name>
      <first>Frederick</first>
      <middle>James</middle>
      <last>Adler</last>
    </name>
    <date_of_birth>March 6, 1958</date_of_birth>
    <gender>male</gender>
    <salary>46,250</salary>
  </faculty_member>  
  
  <faculty_member>
    <name>
      <first>Vivian</first>
      <middle>Arlene</middle>
      <last>Sullivan</last>
    </name>
    <date_of_birth>September 12, 1959</date_of_birth>
    <gender>female</gender>
    <salary>22,500</salary>
  </faculty_member>    

<faculty_members> 

• XML is not a language. It is a set of rules that specify how to create a language.
  
  
• XML's rules specify the syntax that is used for all XML-based languages.
  
  
• XML tags specify the meanings of individual bits of information and describe hierarchies within a collection of information.
  
  
• A particular XML-based language is described by a DTD or an XML Schema that was prepared for that specific language.
  
  
• Humans and computers use DTDs and XML Schemas to understand XML-based languages.
• You should make sure that all your XML files are well formed, which means that they are structured according to the syntax rules of XML.
  
  
• If you are working with a DTD or an XML Schema, you should also make sure that all your XML files are valid, which means each XML file follows the rules that are specified in the associated DTD or XML Schema.
  
  
• To see if your XML is well formed and valid, you use a software program called an XML Parser.
  
  
• Remember that XML can be invalid even if it is well formed.

1. to store and organize information that needs to be displayed in a Web browser
2. to store and organize information that needs to be printed on paper
3. to exchange information between computers.

<TR>
<TD>Joanne Gayle Jones</TD>
<TD>08/28/1955</TD>
<TD>female</TD>
<TD>teacher</TD>
<TD>42,000</TD>
</TR>
<TR>
<TD>Ruth Ann Green</TD>
<TD>08/25/1978</TD>
<TD>female</TD>
<TD>teacher's assistant</TD>
<TD>21,500</TD>
</TR>

• Web sites work more slowly with HTML than with XML.
  
  
• Lots of huge files are being sent around the Internet all the time; these files would be smaller — and they would need to be sent around the Internet less frequently — if XML were being used for Web pages instead of HTML.

• Programmers get together and decide exactly what kind of information needs to be exchanged.
  
  
• These programmers create an XML-based language that is appropriate for their situation, and they write a Document Type Definition (DTD) or an XML Schema that describes this language.
  
  
• The programmers write or obtain programs that can understand XML and can also understand the DTD or the XML Schema (whichever is being used).
  
  
• When one computer needs to give information to another computer, the computer that is giving the information writes a message to the computer that will receive the information. The language used in the message is the XML-based language specified by the DTD or XML Schema.
  
  
• When the other computer receives the message, it can understand the message because it has available the DTD or the XML Schema for the language used in the message.

• XML is a set of rules that specify how to create a language.
  
  
• We refer to languages that follow XML's rules as "XML-based languages."
  
  
• A particular XML-based language is described by a DTD or by an XML Schema.
  
  
• Humans and computers depend on a DTD or an XML Schema to understand a particular XML-based language.
  
  
• XML is good at describing how a collection of information is structured. You can also use XML technology to control how the information is displayed. (We talk about this in the next section.)
  
  
• HTML is good at describing how to display information, but HTML usually doesn't tell you very much about the structure of the information.
  
  
• You can use XML technology to store and organize information that will be displayed on the Web and/or printed on paper and/or exchanged between different computers.
  
  
• Over the next few years, Web programmers will use XML more and more and will use HTML less and less.

• A programmer creates an XSL file that contains instructions for generating code that will present the information in the desired format.
  
  
• The code in the XML file and the code in the XSL file is parsed by an XML Parser and stored in computer memory.
  
  
• The parsed XML code and the parsed XSL code are processed together by a program called an XSL Processor, which produces a file that is used to render the XML information. In the most common scenario, the XSL code contains instructions that tell the XSL Processor to create HTML code. However, it is possible for programmers to write XSL code that tells the XSL Processor to create other types of code. We will talk a little more about this later.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">

<xsl:template match="/">
  <xsl:apply-templates select="faculty_members"/>
</xsl:template>

<xsl:template match="faculty_members">
  <HTML>
    <HEAD>
      <TITLE>faculty_members data displayed in table format</TITLE>
      <BASEFONT FACE="Arial, Helvetica, sans-serif"/>
    </HEAD>
    <BODY>
      <TABLE>
        <TR>
          <TH ALIGN="LEFT">Name</TH>
          <TH ALIGN="LEFT">Date of Birth</TH>
          <TH ALIGN="LEFT">Gender</TH>    
          <TH ALIGN="LEFT">Job Title</TH>
          <TH ALIGN="LEFT">Salary</TH>
        </TR>
        <xsl:for-each select="faculty_member">
          <TR>
            <TD>
              <xsl:value-of select="name/first"/>
              <xsl:value-of select="name/middle"/>
              <xsl:value-of select="name/last"/>
            </TD>
            <TD>
              <xsl:value-of select="date_of_birth"/>
            </TD>
            <TD>
              <xsl:value-of select="gender"/>
            </TD>
            <TD>
              <xsl:value-of select="job_title"/>
            </TD>
            <TD>
              <xsl:value-of select="salary"/>
            </TD>
          </TR>
        </xsl:for-each>
      </TABLE> 
    </BODY>
  </HTML>
</xsl:template>

</xsl:stylesheet>

* * * TIME TO REVIEW * * *

• XML technology allows programmers to separate the task of structuring information from the task of presenting information.
  
  
• Separating structure from presentation can make it easier to write programs.
  
  
• Extensible Stylesheet Language (XSL) is a language that programmers can use to describe how XML information should be presented.
  
  
• To use XSL to present XML information, you need two types of computer programs: an XML Parser and an XSL Processor. The XML Parser analyzes XML code and XSL code and puts it into computer memory, and an XSL Processor uses XML code together with XSL code to create some other type of code.
  
  
• In the typical scenario, the type of code that an XSL Processor creates is HTML code; and the HTML code is use to present the XML information in a browser.

<?xml version='1.0' ?>

<?xml-stylesheet type="text/xsl" href="faculty_members_table.xsl"?>

<faculty_members>

  <faculty_member>
    <name>
      <first>Joanne</first>
      <middle>Gayle</middle>
      <last>Jones</last>
    </name>
    <date_of_birth>08/28/1955</date_of_birth>
    <gender>female</gender>
    <job_title>teacher</job_title>
    <salary>42,000</salary>
  </faculty_member>
  
  <faculty_member>
    <name>
      <first>Ruth</first>
      <middle>Ann</middle>
      <last>Green</last>
    </name>
    <date_of_birth>08/25/1978</date_of_birth>
    <gender>female</gender>
    <job_title>teacher's assistant</job_title>
    <salary>21,500</salary>
  </faculty_member>  
  
  <faculty_member>
    <name>
      <first>Vincent</first>
      <middle>John</middle>
      <last>Pellio</last>
    </name>
    <date_of_birth>07/16/1959</date_of_birth>
    <gender>male</gender>
    <job_title>teacher</job_title>
    <salary>36,500</salary>
  </faculty_member>    
  
</faculty_members>

<?xml-stylesheet type="text/xsl" href="faculty_members_table.xsl"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">

<xsl:template match="/">
  <xsl:apply-templates select="faculty_members"/>
</xsl:template>

<xsl:template match="faculty_members">
  <HTML>
    <HEAD>
      <TITLE>faculty_members data displayed in table format</TITLE>
      <BASEFONT FACE="Arial, Helvetica, sans-serif"/>
    </HEAD>
    <BODY>
      <TABLE>
        <TR>
          <TH ALIGN="LEFT">Name</TH>
          <TH ALIGN="LEFT">Date of Birth</TH>
          <TH ALIGN="LEFT">Gender</TH>    
          <TH ALIGN="LEFT">Job Title</TH>
          <TH ALIGN="LEFT">Salary</TH>
        </TR>
        <xsl:for-each select="faculty_member">
          <TR>
            <TD>
              <xsl:value-of select="name/first"/>
              <xsl:value-of select="name/middle"/>
              <xsl:value-of select="name/last"/>
            </TD>
            <TD>
              <xsl:value-of select="date_of_birth"/>
            </TD>
            <TD>
              <xsl:value-of select="gender"/>
            </TD>
            <TD>
              <xsl:value-of select="job_title"/>
            </TD>
            <TD>
              <xsl:value-of select="salary"/>
            </TD>
          </TR>
        </xsl:for-each>
      </TABLE> 
    </BODY>
  </HTML>
</xsl:template>

</xsl:stylesheet>

<HTML>
<HEAD>
<TITLE>faculty_members data displayed in table format</TITLE>
<BASEFONT FACE="Arial, Helvetica, sans-serif"/>
</HEAD>
<BODY>
<TABLE>
<TR>
<TH ALIGN="LEFT">Name</TH>
<TH ALIGN="LEFT">Date of Birth</TH>
<TH ALIGN="LEFT">Gender</TH>
<TH ALIGN="LEFT">Job Title</TH>
<TH ALIGN="LEFT">Salary</TH>
</TR>
<TR>
<TD>Joanne Gayle Jones</TD>
<TD>08/28/1955</TD>
<TD>female</TD>
<TD>teacher</TD>
<TD>42,000</TD>
</TR>
<TR>
<TD>Ruth Ann Green</TD>
<TD>08/25/1978</TD>
<TD>female</TD>
<TD>teacher's assistant</TD>
<TD>21,500</TD>
</TR>
<TR>
<TD>Vincent John Pellio</TD>
<TD>07/16/1959</TD>
<TD>male</TD>
<TD>teacher</TD>
<TD>36,500</TD>
</TR>
</TABLE>
</BODY>
</HTML>

<?xml version='1.0' ?>

<?xml-stylesheet type="text/xsl" href="faculty_members_sentences.xsl"?>

<faculty_members>

  <faculty_member>
    <name>
      <first>Joanne</first>
      <middle>Gayle</middle>
      <last>Jones</last>
    </name>
    <date_of_birth>08/28/1955</date_of_birth>
    <gender>female</gender>
    <job_title>teacher</job_title>
    <salary>42,000</salary>
  </faculty_member>
  
  <faculty_member>
    <name>
      <first>Ruth</first>
      <middle>Ann</middle>
      <last>Green</last>
    </name>
    <date_of_birth>08/25/1978</date_of_birth>
    <gender>female</gender>
    <job_title>teacher's assistant</job_title>
    <salary>21,500</salary>
  </faculty_member>  
  
  <faculty_member>
    <name>
      <first>Vincent</first>
      <middle>John</middle>
      <last>Pellio</last>
    </name>
    <date_of_birth>07/16/1959</date_of_birth>
    <gender>male</gender>
    <job_title>teacher</job_title>
    <salary>36,500</salary>
  </faculty_member>    
  
</faculty_members>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">

<xsl:template match="/">
  <xsl:apply-templates select="faculty_members"/>
</xsl:template>

<xsl:template match="faculty_members">
  <HTML>
    <HEAD>
      <TITLE>faculty_members data displayed in sentence format</TITLE>
      <BASEFONT FACE="Arial, Helvetica, sans-serif"/>     
    </HEAD>
    <BODY>
      <xsl:for-each select="faculty_member">
        <xsl:value-of select="name/first"/>
        <xsl:value-of select="name/middle"/>
        <xsl:value-of select="name/last"/>
        is a
        <xsl:value-of select="gender"/>
        <xsl:value-of select="job_title"/>
        who was born on
        <xsl:value-of select="date_of_birth"/>
        and earns 
        $<xsl:value-of select="salary"/>
        per year.<BR/><BR/>
      </xsl:for-each>
    </BODY>
  </HTML>
</xsl:template>

</xsl:stylesheet>

<HTML>
<HEAD>
<TITLE>faculty_members data displayed in sentence format</TITLE>
<BASEFONT FACE="Arial, Helvetica, sans-serif" />
</HEAD>
<BODY>
Joanne Gayle Jones is a female teacher 
who was born on
08/28/1955
and earns 
$42,000
per year.<BR />
<BR />
Ruth Ann Green is a female teacher's 
assistant who was born on
08/25/1978
and earns 
$21,500
per year.<BR />
<BR />
Vincent John Pellio is a male teacher
who was born on
07/16/1959
and earns 
$36,500
per year.<BR />
<BR />
</BODY>
</HTML>

• An XSL Processor uses XML code and XSL code to produce some other kind of code - typically HTML code.
  
  
• If you have an XSL Processor, you can use several different XSL files to present the same XML information in several different ways.
  
  
• Some Internet browsers have a built-in XSL Processor.

• If you are developing a Web site for an environment where all your site visitors will be using browsers that have built-in XSL Processors, then your job will be relatively easy. Your Web server can send XML code directly to your visitors' browsers, along with "<xsl:stylesheet>" commands that reference XSL files. Each visitor's browser will use its built-in XSL Processor to process the XML code and the XSL code, producing HTML code.
  
  This is the technique that we used above for the "faculty_members" examples.
  
  This setup will work if, for example, you are developing a site to be used only by employees of a corporation where everybody uses a current version of the Microsoft Internet Explorer browser.
  
  
• If you are developing a Web site that can be used by anybody in the world, then your job will be more challenging; because some of your visitors will have a browser without a built-in XSL Processor. You can't send XML code to your visitors' browsers.
  
  There are a few ways to handle this situation, one of which is the following: use an XSL Processor on the Web server to generate HTML code from XML code and XSL code; then send the HTML code to your visitors' browsers. For this type of system, you can use the XSL Processor in "XMLwriter" or "Cocoon," both of which are described below.
  
  This setup will work if, for example, you are developing a Web site for marketing and selling products or services on the Internet.

• XMLwriter. This is an XML editor with an XSL Processor built into it. You can use XMLwriter's XSL Processor interactively, from XMLwriter's graphical user interface; you can also use the XSL Processor non-interactively, from the command line.
  
  XMLwriter runs under Windows 95/98/NT/2000. It is easy to install and easy to use. XMLwriter is a very nice tool for learning about XML technology and for doing serious work with XML technology. When you use XMLwriter for editing, it displays color coding that helps you to catch typing errors when you are typing XML code, XSL code, DTD code, and some other kinds of code ̬ including HTML.
  
  In addition to what we've described here, XMLwriter performs many other useful tasks. And XMLwriter has an excellent on-line XML reference guide.
  
  XMLwriter is available from Wattle Software at http://xmlwriter.net. It costs $42.00. You can download a 30-day-trial version for free.
  
  
• Cocoon. This a Java publishing "framework" that programmers can use to develop XML-based Web sites. Cocoon can do many things, one of which is to function as an XSL Processor.
  
  Cocoon is more difficult to install than XMLwriter.
  
  Cocoon runs on many different kinds of computers. You can download it for free from http://cocoon.apache.org/2.0//, and you can use it for free as long as you abide by the terms of the license agreement.

• You can present XML information in Braille format.
  
  
• You can use "text-to-speech" technology that presents XML information to Web site visitors by talking to them.
  
  
• You can convert XML information to various document formats, such as PDF (Adobe's Portable Document Format), RTF (Microsoft's Rich Text Format), and others.
  
  
• You can format XML information for presentation on cellular phones and on Personal Digital assistants (PDAs) like the Palm devices.

www.xml.com - This Web site features a mix of information and services for the XML community.

www.objectinnovations.com - This is the corporate Web site for Object Innovations, a company that offers excellent training materials for XML-related technologies.

www.xml.org - Go to this Web site to use the XML.ORG Registry, which lets you access the fast-growing body of XML specifications, schemas and vocabularies that are being developed.

www.w3c.org - This is the Web site for the World Wide Web Consortium (W3C), which develops interoperable technologies (specifications, guidelines, software, and tools) to lead the Web to its full potential.

www.ibiblio.org/xml/books/bible2/chapters/ch18.html - This link takes you to Chapter 18 of the XML Bible by Elliotte Rusty Harold. This chapter of the XML Bible talks in detail about XSL Formatting Objects (XSL-FO) and explains how to use the XSL-FO technology.

http://webreference.com/xml/ - This area of the webreference.com site contains lots of information about XML and about XML-related technologies. Most of this information is written in a down-to-earth style that can be understood easily.

http://cocoon.apache.org/2.0/ - This is the Web site for the Cocoon Project. You can get the Cocoon XSL Processor here.

http://xmlwriter.net - This is the Web site for Wattle Software. You can get the XMLwriter software here.

www.arbortext.com - This is the Web site for Arbortext, a leading provider of XML-based information applications.

www.w3.org/TR/WAI-WEBCONTENT-TECHS/#structure - This is a link to a document entitled "Techniques for Web Content Accessibility Guidelines 1.0." It talks about how to make Web sites accessible to the disabled community.