A DTD Example

Because being able to create DTDs is an essential XML skill these days (at least, until XML schemas are widely supported), I'll work through another example here.

This new example is a model for a book, complete with <CHAPTER>, <SECTION>, <PART>, and <SUBTITLE> elements. Here's what the document will look like:

<?xml version="1.0"?>
<!DOCTYPE BOOK [
    <!ELEMENT p (#PCDATA)>
    <!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
    <!ELEMENT OPENER       (TITLE_TEXT)*>
    <!ELEMENT TITLE_TEXT   (#PCDATA)>
    <!ELEMENT SUBTITLE     (#PCDATA)>
    <!ELEMENT INTRODUCTION (HEADER, p+)+>
    <!ELEMENT PART         (HEADER, CHAPTER+)>
    <!ELEMENT SECTION      (HEADER, p+)>
    <!ELEMENT HEADER       (#PCDATA)>
    <!ELEMENT CHAPTER      (CHAPTER_NUMBER, CHAPTER_TEXT)>
    <!ELEMENT CHAPTER_NUMBER (#PCDATA)>
    <!ELEMENT CHAPTER_TEXT (p)+>
]>
<BOOK>
    <OPENER>
        <TITLE_TEXT>
            All About Me
        </TITLE_TEXT>
    </OPENER>
    <PART>
        <HEADER>Welcome To My Book</HEADER>
        <CHAPTER>
            <CHAPTER_NUMBER>CHAPTER 1</CHAPTER_NUMBER>
            <CHAPTER_TEXT>
                <p>Glad you want to hear about me.</p>
                <p>There's so much to say!</p>
                <p>Where should we start?</p>
                <p>How about more about me?</p>
            </CHAPTER_TEXT>
        </CHAPTER>
    </PART>
</BOOK>

In this case, I'll start the DTD by declaring the <p> element, which I want to hold text only—that is, PCDATA, which you specify with #PCDATA:

<!ELEMENT p            (#PCDATA)>
        .
        .
        .

Next, I'll declare the <BOOK> element, which is the root element. In this case, the <BOOK> element contains an <OPENER> element, possibly a <SUBTITLE> element, possibly an <INTRODUCTION> element, and one or more sections or parts declared with the <SECTION> and <PART> elements:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
        .
        .
        .

Now I will declare the <OPENER> element. This element will hold the title text for the chapter, which I'll store in <TITLE_TEXT> elements:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
        .
        .
        .

I'll declare the <TITLE_TEXT> element so that it contains plain text:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
        .
        .
        .

And I declare the <SUBTITLE> element, which must also contain PCDATA:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
<!ELEMENT SUBTITLE     (#PCDATA)>
        .
        .
        .

I'll set up the <INTRODUCTION> element so that it contains a <HEADER> element and so that it must contain one or more <p> elements. I'll then allow that sequence to repeat, like this:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
<!ELEMENT SUBTITLE     (#PCDATA)>
<!ELEMENT INTRODUCTION (HEADER, p+)+>
        .
        .
        .

Next, the <PART> element contains a <HEADER> and one or more <CHAPTER> elements:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
<!ELEMENT SUBTITLE     (#PCDATA)>
<!ELEMENT INTRODUCTION (HEADER, p+)+>
<!ELEMENT PART         (HEADER, CHAPTER+)>
        .
        .
        .

In addition, I'll specify that the <CHAPTER> element must contain a <CHAPTER_NUMBER> and <CHAPTER_TEXT> element:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
<!ELEMENT SUBTITLE     (#PCDATA)>
<!ELEMENT INTRODUCTION (HEADER, p+)+>
<!ELEMENT PART         (HEADER, CHAPTER+)>
<!ELEMENT SECTION      (HEADER, p+)>
<!ELEMENT HEADER       (#PCDATA)>
    <!ELEMENT CHAPTER  (CHAPTER_NUMBER, CHAPTER_TEXT)>
        .
        .
        .

The <CHAPTER_NUMBER> element contains parsed character data:

<!ELEMENT p            (#PCDATA)>
<!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
<!ELEMENT OPENER       (TITLE_TEXT)*>
<!ELEMENT TITLE_TEXT   (#PCDATA)>
<!ELEMENT SUBTITLE     (#PCDATA)>
<!ELEMENT INTRODUCTION (HEADER, p+)+>
<!ELEMENT PART         (HEADER, CHAPTER+)>
<!ELEMENT SECTION      (HEADER, p+)>
<!ELEMENT HEADER       (#PCDATA)>
<!ELEMENT CHAPTER  (CHAPTER_NUMBER, CHAPTER_TEXT)>
<!ELEMENT CHAPTER_NUMBER (#PCDATA)>
        .
        .
        .

Finally, the <CHAPTER_TEXT> element can contain <p> paragraph elements:

    <!ELEMENT p (#PCDATA)>
    <!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
    <!ELEMENT OPENER       (TITLE_TEXT)*>
    <!ELEMENT TITLE_TEXT   (#PCDATA)>
    <!ELEMENT SUBTITLE     (#PCDATA)>
    <!ELEMENT INTRODUCTION (HEADER, p+)+>
    <!ELEMENT PART         (HEADER, CHAPTER+)>
    <!ELEMENT SECTION      (HEADER, p+)>
    <!ELEMENT HEADER       (#PCDATA)>
    <!ELEMENT CHAPTER      (CHAPTER_NUMBER, CHAPTER_TEXT)>
    <!ELEMENT CHAPTER_NUMBER (#PCDATA)>
    <!ELEMENT CHAPTER_TEXT (p)+>

And that's it; the DTD is finished. Here's how it looks in the <!DOCTYPE> element in the complete document:

<?xml version="1.0"?>
<!DOCTYPE BOOK [
    <!ELEMENT p (#PCDATA)>
    <!ELEMENT BOOK         (OPENER,SUBTITLE?,INTRODUCTION?,(SECTION | PART)+)>
    <!ELEMENT OPENER       (TITLE_TEXT)*>
    <!ELEMENT TITLE_TEXT   (#PCDATA)>
    <!ELEMENT SUBTITLE     (#PCDATA)>
    <!ELEMENT INTRODUCTION (HEADER, p+)+>
    <!ELEMENT PART         (HEADER, CHAPTER+)>
    <!ELEMENT SECTION      (HEADER, p+)>
    <!ELEMENT HEADER       (#PCDATA)>
    <!ELEMENT CHAPTER      (CHAPTER_NUMBER, CHAPTER_TEXT)>
    <!ELEMENT CHAPTER_NUMBER (#PCDATA)>
    <!ELEMENT CHAPTER_TEXT (p)+>
]>
<BOOK>
    <OPENER>
        <TITLE_TEXT>
            All About Me
        </TITLE_TEXT>
    </OPENER>
    <PART>
        <HEADER>Welcome To My Book</HEADER>
        <CHAPTER>
            <CHAPTER_NUMBER>CHAPTER 1</CHAPTER_NUMBER>
            <CHAPTER_TEXT>
                <p>Glad you want to hear about me.</p>
                <p>There's so much to say!</p>
                <p>Where should we start?</p>
                <p>How about more about me?</p>
            </CHAPTER_TEXT>
        </CHAPTER>
    </PART>
</BOOK>

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
3.128.91.252