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This module is part of a collection dedicated to learning XML.

Table of contents

Preface

General

This tutorial lesson is part of a series dedicated to learning XML.

Viewing tip

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the figures and listings whileyou are reading about them.

Figures

Listings

Supplemental material

I recommend that you also study the other lessons in my extensive collection of online programmingtutorials. You will find a consolidated index at www.DickBaldwin.com .

Tags, elements, content, and attributes

XML can be used to produce a variety of applications. Flex is an XML application developed by Adobe that can be used to produce code that will run inthe Adobe Flash player.

Listing 1 shows the code from a very simple Flex MXML file. (Note that the code shown in Listing 1 is from Flex version 3.x. Code from version 4.xwould be different in several respects.)

Listing 1 . Simple Flex MXML code.
<?xml version="1.0" encoding="utf-8"?><!--DragAndDrop04--><mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"xmlns:cc="CustomClasses.*"><cc:Driver/></mx:Application>

I'm not going to explain the MXML code in this lesson. I am simply providing thecode as an example of an XML document so you can see what a real XML document looks like.

What is a tag?

I will refer to items enclosed in angle brackets, such as those shown in Figure 1, as tags.

Figure 1 . Tag example.
<book>...</book>

The first tag shown in Figure 1 is often referred to as a start tag or an opening tag . The second tag is often referred to as an end tag or a closing tag .

Note that the start tag and the end tag differ only in that the end tag contains a slash character. However, the start tag can also contain optionalnamespace indicators and attributes as discussed below.

What are elements, content, and attributes?

Listing 2 contains a start tag and an end tag with an attribute and some content .

Listing 2 . An element containing tags, content, and an attribute.
<chap number="1">Text for Chapter 1</chap>

An element

The entire set of characters beginning with the start tag and ending with the end tag constitutes an element .

An element usually consists of a start tag and an end tag with the content sandwiched in between the two tags, but there are exceptions to that rule. Youwill learn about those exceptions, including empty elements later.

The tags

You have probably already recognized the tags in Listing 2 as the two sets of characters beginning with a left angle bracket and ending with a right anglebracket.

The start tag may contain optional attributes. In Listing 2, a single attribute provides the number value for the chapter.

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
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Source:  OpenStax, Introduction to xml. OpenStax CNX. Dec 02, 2014 Download for free at https://legacy.cnx.org/content/col11207/1.18
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