Theses names are all lowercase, full words, no plurals?and easy set of criteria to remember.

When you think about elements, think about the role they play and the data they contain. Don’t think about how the elements will look on the page. Appearance is handled separately.

You are using elements to identify data within your document as playing a certain role or belonging to a certain category of data.

After you data is marked up, you’ll use style sheets or other processing tools to display the XML document. You can control the display based on information contained in the elements.

In a valid XML document, only the elements which are specified in the DTD will pass muster. If you randomly add other elements, their use will be flagged as an error.

When you use elements in an XML document, you must follow standard XML syntax:

• The element name surrounds the data which it defines. For example: Tying Knots.
• All elements, including empty elements, must end. This means having an open and close tag for regular elements and a tag that closes with a slash for empty elements.
• The element name is case sensitive: ,is not the same as .

One of the ways to define and codify all your elements is to create a DTD. A DTD defines the allowable elements, their attributes (if any) are, and their relationship is to other elements.

By validating your XML document against a DTD, you can test to be sure that elements in the documents are being used correctly.

Attributes
Attributes provide additional information about elements.

You use elements and attributes all the time in HTML. For example, in HTML, a tag such as

includes an element: H1, and an attribute: align and an attribute value: center.

In HTML, attributes allow you to specify additional information about your elements. Often this information is formatting-related, such as align or size. In XML, attributes allow you to specify additional data about an element, but it is never formatting-related. It is, instead, additional data about that particular element.

Let’s say, for example, you’re creating documents about late 20th century popular music. In your DTD you’ve created an element called which identifies each musical title. You have music that falls into different decade categories — the 70’s, the 80’s and the 90’s. You can give the song element an attribute called era. Now, you’ll be able to know from what era each song dates.

By using an attribute, you can identify different versions of the same song — “I’ve Got You Babe” from the 1960s and “I’ve Got You Babe” from the 1980s. Later on, you can use this data to display all 70s songs in green, or to sort the displayed titles by era.

You would use the attribute like this:

I’ve Got You Babe

Billy Don’t Be a Hero

I’ve Got You Babe

“I’ve Got You Babe” is identified as a “song” element with an “era” attribute value of “60s”. “Billy Don’t Be A Hero” is identified as a “song” element with an “era” attribute value of “70s”. “I’ve Got You Babe” is identified as a “song” element with an “era” attribute value of “80s”.

Attributes and their allowable values are created in your DTD, when you specify elements. They are specified through an attribute list. Like element names, attribute names are case-sensitive, so be aware of your use of capitalization when you select and use attribute names.

One other important thing to remember about attributes in XML tags is that the attribute values must always be contained inside quotes. In HTML it’s a mixed bag, but in XML the rule is easy to remember: quote all attribute values.

Comments
Comments are a way to add your own notes to an XML document. The browser and the XML processors will ignore anything inside comments.

You aren’t going to remember what you were thinking three months later when you return to edit the document, so don’t be afraid to add comments as reminders or as markers of work that you have done.

To create a comment:

1. Type a less than sign, followed by an exclamation point and two dashes like this:

CDATA
CDATA stands for “character data.” Character data are letters, numbers, and other symbols that are used exactly as they are typed. They are not parsed or processed, or treated as if they have any special meaning.

You can create a CDATA section within your XML document. A CDATA section is handy way to show code examples or to use characters, such as > that would otherwise take on a special meaning. You can use CDATA instead of using a series of <, for example.

To create a CDATA section:

1. At the place in the document where you want the CDATA section to appear, begin a CDATA definition with the less than sign and an exclamation point.

2. Type an open square brace and the letters CDATA.

   [CDATA

3. Type another open square brace.

   [

4. Now type the CDATA itself. In this example, we are typing some sample code.

   Sir Fredrick of Ledyard’s End

5. End the section with two closing square bracket and a greater than symbol.

   Sir Fredrick of Ledyard’s End]]>

Click anywhere on this code to see how it would be displayed in a browser, assuming of course, that it is linked to a stylesheet:

Entering a Kennel Club Member



Enter the member by the name on his or her papers. Use the NAME tag. The NAME tag has two attributes. Common (all in lowercase, please!) is the dog’s call name. Breed (also in all lowercase) is the dog’s breed. Please see the breed reference guide for acceptable breeds. Your entry should look something like this:



Sir Fredrick of Ledyard’s End]]>

Namespaces
Namespaces are a way of using elements from more than one DTD within the same XML document.

Sometimes you may be working with material that draws on several sets of element tags. For example, you might have an online store selling tropical fish and you’d like to use the tag to identify both the geographic location from which each species comes and the wholesaler from whom you buy it. Namespaces are a way to do this.

An XML namespace is a collection of names, identified by a URI reference, which are used in XML documents as element types and attribute names. In practice, namespaces let you match a tag you are using with a particular set of tags.

In the beginning of your document (or at the start of a particular element of your document), you identify the namespaces you’ll be using and where the tag information is located. Then, when you use the tag to identify an element in your document, you precede it with the appropriate namespace name.

Declaring Namespaces
At the beginning of your document, you’ll want to identify the namespaces you are using in your document. This process is called declaring the namespace. In this example, you are creating a namespace called “sales.” The URI for sales is the mythical fishworld.org/schema:

Using Namespaces
When you use the tag to create the element that is defined in one of the namespaces, the namespace is the first part of the tag, like this:

Fish-o-Rama Wholesalers and Suppliers to the Trade

When you use your own tag you just use the tag name, like this:

Mexico, Central America

In January 1999, Namespaces became a W3C recommendation.

XML Entities
An entity is a short cut to a set of information.

When you use an entity, it “expands” to its full meaning, but you need only type the shorter entity name during data entry. You might think of an entity as being a bit like a macro?it is a set of information that can be used by calling one name.

XML defines two types of entities. The general entity, which we’ll talk about here, is used in XML document. The parameter entity is used in DTDs. General entities are easy to spot: they begin with the ampersand and end with the semicolon, like this:

&entity-name;

Uses for Entities
Entities are a way to make entering and managing data easier.

You’ve probably already used entities without calling them that. If you’ve ever entered the characters < to create the < symbol, you've used an entity. This keystroke combination is a standard predefined entity in both HTML and XML that lets you access a particular ascii character without having to memorize the character set number.

Here are a few reasons you might want to define and use entities:

• Entities save typing. Suppose you have a paragraph, like a copyright notice, that you use in every single document. You could type that notice over and over again. Or, you could use an entity to call it forth in place.
• Entities can reduce errors. By the 101st time you type that copyright notice, it is likely your poor fingers will be so tired you’ll make an error and set your copyright for 1989 instead of 1999. Using an entity can reduce the potential for these types of errors.
• Entities are easy to update. It is time to update that copyright notice?with an entity you can make the change in one place and be done with it. Without an entity you’d be searching and replacing throughout your document set.
• Entities can act as placeholders for TBD information. Maybe legal hasn’t quite finalized what they want that copyright notice to say. That doesn’t have to stop production?you can use and entity and when the final wording comes down, the entity will automatically display the new, corrected version in all your documents.

You can get quite creative with the use of entities, and even have documents that are constructed entirely from entities. Here’s an example:

You want to create different documents, each contains a set of bios for members of your staff. You’ll have an executive set, a set for each product line, a set for six different regions around the world … subsets of the same content appears in each.

One approach you could take is creating 10 or 12 separate flat files, with the appropriate biography information into each. But an easier way is to create a small file for each bio, then call each into the executive page, the European page, the Flying Toys Division page and so on via an entity.

Here’s how the content code for your Flying Toys Division Page might look. Upon display, the entities would expand and you’d see the full bios of each person. If you needed to change the bios, you could do it in one place. If the product manager changed, all your pages would be automatically updated with the new person.

Click anywhere in the code to see how it might expand into a displayed document:

The Faces Behind Flying Toys!
&bio-ft-div-head;
&bio-ft-prod-mgr;
&bio-ft-designer;
&bio-ft-lead-engineer;

Defining Entities
You can define entities in your local document as part of the DOCTYPE definition. You can also link to external files that contain the entity data. This, too, is done through the DOCTYPE definition. A third option is to define the entities in your external DTD.

Use a local definition when the entity is being used only in this one particulars file. Use a linked, external file when the entity being used in many document sets.

To define an entity:

1. Start your DOCTYPE definition as usual, like this:

2. Now mark that you are defining some data by entering a square bracket:

3. Start the entity definition, with a less than sign, an exclamation mark, and the phrase ENTITY, all in caps:

4. Type the name of the entity. Type it using the capitalization that you will use when calling it later on.

5. If you are defining the entity locally, type the value of the entity, surrounded by quotes, and then close the entity definition with a greater than sign.

6. If you are defining an entity in an external, ascii text file, put in a pointer to the external file, then close the entity definition with a greater than sign.

7. Create all your entity definitions. When you are done, close the DOCTYPE definition with a square brace and a greater than sign.

   
   
   ]
   >

Using Entities

To use an entity in your document, just call it by name. The name begins with an & and ends with a semi-colon.

Click anywhere on this code to see how it would display, assuming of course, that it was linked to a style sheet.

]
>



Mini-globe revolutionizes keychain industry


Today As The World Spins introduces a new approach to key chains. With the new MINI-GLOBE keys can be kept inside a chain, called for upon demand, and stored safely. Never more will consumers lose a key or stand at a door flipping through a stack of keys seeking the right one.


&trademark;
&copyright;