Element Declarations in .NET

Scan QR Code ISO/IEC18004 in .NET Element Declarations

You declare XML elements in the markupdecl section of the DTD: doctypedecl::= '<!DOCTYPE' S Name (S ExternalID)

S ('[' markupdecl* ']' S ) '>'

%NotationDecl | %conditionalSect | %PI | %S | %Comment )* )

Here's how you declare elements formally: elementdecl::= '<!ELEMENT' S %Name %S %contentspec S '>'

If your elements can contain both other elements and character data, you declare them with mixed content: Mixed::= '(' S %( %'#PCDATA' ( S '|' S %(%Name

(S '|' S %Name)*) )* ) S ')*' | '(' S %('#PCDATA') S ')' '*'

If your elements can only contain other elements, you declare them this way: elements::= (choice | seq) (' ' | '*' | '+')

cp::= (Name | choice | seq) (' ' | '*' | '+')

choice::= '(' S %(cps ('|' cps)+) S ')'

seq::= '(' S %(cps (', ' cps)*) S ')'

We saw an example of a DTD earlier in this chapter when we discussed external DTDs Let's put that DTD inside the document now to create a new file, +, so we can dissect this new example We start the DTD in dtdxml with the DOCTYPE keyword and enclose the actual declarations inside square braces, [ and ]:

<!DOCTYPE Thesis [

In this case, we're declaring an element of type Thesis that can contain zero or more <p> tags We also declare the <p> tag to contain character data That's an example of a simple DTD Let's go on now to a more complex example

<!DOCTYPE DOCUMENT [

Let's take a closer look at the DTD of this document now To start, we declare the root element, <DOCUMENT>, which can contain zero or more <CUSTOMER> tags: <!DOCTYPE DOCUMENT [

Now we declare the <CUSTOMER> tag, which contains, in this order, the following tags: <NAME>, <DATE>, and <ORDERS>: <!DOCTYPE DOCUMENT [

Then we declare the <NAME> tag and indicate that this tag contains <LASTNAME> and <FIRSTNAME> tags, again in that order: <!DOCTYPE DOCUMENT [

We also declare the <LASTNAME>, <FIRSTNAME>, and <DATE> tags to contain character data: <!DOCTYPE DOCUMENT [

The <ORDERS> tag is next, and it contains zero or one <ITEM> tags: <!DOCTYPE DOCUMENT [

The <ITEM> tag contains a <PRODUCT>, <NUMBER>, and <PRICE> tag in that order: <!DOCTYPE DOCUMENT [

The <PRODUCT>, <NUMBER>, and <PRICE> tags contain character data: <!DOCTYPE DOCUMENT [

We can write an application[md]dtd2java on the CD-ROM[md]that parses this example, dtd2 xml, like this: import commsxmlParseException;

import commsxmlDocument;

import commsxmlElement;

import javautilEnumeration;

import javanet*;

static String filename;

public static void main(String args[])

filename = "file:////c://xml//dtd2//dtd2xml";

URL url = null;

try {

url = new URL(filename);

catch (MalformedURLException ex) {

Systemoutprintln("Cannot create URL for: " + filename);

Systemexit(0);

Document d = new Document();

try {

dload(url);

catch (ParseException e) {

dreportError(e, Systemout);

Systemexit(0);

if (d != null) {

Systemoutprintln(filename + " parsed OK");

When you run this program, it parses the document and its DTD, indicating that the document parsed without trouble That's it[md]now our dtd2xml example is complete Let's take a look at one more [md]and still more complex[md]DTD example now

In this case, we have a number of elements: <DOCUMENT>, <TITLE>, <PART>, <HEADING>, and so on The DTD for this file will be dtd3dtd, and we start that file by declaring the <p> element: <!ELEMENT p (#PCDATA)>

Next, we declare the root element, <DOCUMENT> We declare the <DOCUMENT> element to contain a <TITLE> tag, possibly a <SUBTITLE> tag (by placing a after the SUBTITLE declaration), possibly a <PREFACE> tag, and one or more sections or parts as declared with the <SECTION> or <PART> tags this way: <!ELEMENT p (#PCDATA)>

Next, we declare a <TITLE> tag that contains zero or more occurrences of character data and <TITLE2> tags: <!ELEMENT p (#PCDATA)>