What are the differences between XML and HTML? What are the advantages of XML?

First, XML guide

XML is a software and hardware-independent information transfer tool. X ML is the recommended standard for W3C. XML is ubiquitous, and when we see the rapid pace of development of the XML standard, and the large number of software developers taking it at a rapid pace, it's really amazing.

Today, XML is no less effective in the Web than HTML, which has always been the cornerstone of the Web. X ML is the most frequently used tool for data transfer between programs and is becoming increasingly popular in the field of information storage and description. To learn XML, you can use the XML.DOM tutorial

Second, XML basic overview

XML (expandable markup language), a subset of standard universal markup languages, is a markup language used to mark electronic files to make them structural. In an electronic computer, a marker is an information symbol that a computer can understand, and by doing so, a computer can process information that includes a variety of information, such as articles.

It can be used to tag data, define data types, and is a source language that allows users to define their own markup language. I t is ideal for World Wide Web transmission, providing a unified way to describe and exchange structured data independently of the utilizing program or vendor. i s a cross-platform, content-dependent technology in an Internet environment and an effective tool for dealing with distributed structured information today. As early as 1998, W3C released the XML 1.0 specification, which is used to simplify the transfer of document information over the Internet.

Third, what is XML?

1. XML refers to the expandable markup language (EXtensible Markup Language)
2. XMl is a markup language that is very similar to HTML (hypertext markup language)
3. XML is designed to transfer data, not display it
4. XML labels are not predefined and you need to define them yourself
5. XML is designed to be self-descriptive
6. XML is the recommended standard for W3C

The main differences between XML and HTML

1. XML and HTML are designed for different purposes
2. XML is designed to transfer and store data, focusing on the content of the data
3. HTML is designed to display data, focusing on the appearance of the data
4. HTML is designed to display information, while XML is intended to transmit information
5. XML is not a replacement for HTML, it complements HTML
6. It's important to understand that XML doesn't replace HTML. In most Web takers, XML is used to transfer data, while HTML is used to format and display data

V. Why XML is needed

1. Fixes an irregular data transfer issue
2. Things that can describe tree structures very well
3. Can be used as a profile

XML without any action

XML is inaction. I t may be a little hard to understand, but XML doesn't do anything. XML is designed to structure, store, and transfer interest.

Let's give you a simple example of what we've written in a note book.

Here is a list of books stored as XML:

The note above is self-descriptive. I t has a title and message, and includes information about the sender and recipient. H owever, this XML document still does nothing. I t is simply information wrapped in XML labels. We need to write software or programs to transmit, receive, and display this document.

XML is just plain text

XML is nothing special. I t's just plain text. S oftware that has the ability to handle plain text can handle XML. H owever, applications that can read XML can target XML labels. T he functional significance of labels depends on the characteristics of the utilizing program. We'll see what XML tags do in future content.

Eight, through XML you can invent your own label

The labels in the example above are not defined in any XML standard (e.g. and <price >, etc.). T hese labels were invented by the author of the document. T his is because XML does not have a predefined label. XML allows authors to define their own labels and their own document structures.

The labels (and the structure of HTML) used in HTML are predefined. HTML documents use only labels defined in HTML standards (such as < p>, < h1>, and so on).

Nine, XML tree structure

As we can see in the book example above, XML documents form a tree structure that starts at the root and then expands to "branches and leaves."

An instance of an XML document

XML uses simple, self-descriptive syntax:

The first line is the XML declaration. I t defines the version of XML (1.0) and the encoding used (UTF-8, GBK, etc.);

The next line describes the root elements of the document (like, "This document is a note"): <note >;

The next four lines describe the four child elements of the root (to, from, heading, and body):
<to>George</to>
<from>John</from>

<heading>Reminder</heading>
<body>Don't forget the meeting!</body>；

The last line defines the end of the root element: </note >.

As you can imagine from this example, the XML document includes a note john gave George.

XML is excellent for self-description, do you agree?

XML documents form a tree structure

The XML document must include the root element. The element is the parent of all other elements.

Elements in an XML document make up a document tree. The tree starts at the root and expands to the bottom of the tree.

All elements can have child elements:

Terms such as parent, child, and sibling are used to describe the relationship between elements. T he parent element has child elements. C hild elements at the same level become siblings (brothers or sisters). All elements can have text content and properties (similar to in HTML).

instance:

The image above represents a book in the following XML:

The root element in the example is < bookstore >. A ll < book > elements in the document are included in the < bookstore >. <book > elements have four child elements:

<title>、< author>、<year>、<price>。

X, XML useful

XML is often used to simplify the storage and sharing of data

(1) XML separates data from HTML

If you need to display dynamic data in an HTML document, you'll spend a lot of time editing HTML whenever the data changes. X ML enables data to be stored in separate XML files. T his allows you to focus on laying out and displaying html and making sure that modifying the underlying data eliminates any need to make any changes to HTML. By using a few lines of JavaScript, you can read an external XML file and then update the contents of the data in HTML.

（2） X ML simplifies data sharing

In the real world, computer systems and data are stored in incompatible formats. X ML data is stored in plain text, providing a software- and hardware-independent data storage method. This makes it easier to create data that different users can share.

(3) XML simplifies data transfer

XML makes it easy to exchange data between incompatible systems. O ne of the most time-consuming challenges for developers has been the exchange of data between incompatible systems on the Internet. Because data can be read through a variety of incompatible exploits, the complexity of exchanging data in XML reduces this complexity.

(4) XML simplifies the change of platform

Upgrading to a new system (hardware or software platform) is always time-consuming. L arge amounts of data must be converted, and incompatible data is often lost. X ML data is stored in text format. This makes it easier for XML to expand or upgrade to a new operating system, new exploits, or new browser without losing data.

(5) XML makes your data more useful

Because XML is independent of hardware, software, and leverage programs, XML makes your data more available and useful. D ifferent consumers have access to your data, not just on HTML pages, but also from XML data sources. XML makes your data available for a variety of browsing devices (handheld computers, voice devices, news browsers, etc.) and for the blind or other disabled.

(6) XML is used to create a new Internet language

Many new Internet languages are created through XML, including:

• XHTML - The latest HTML version
• WSDL - used to describe available web services
• WAP and WML - the markup language for handheld devices
• RSS - The language used for RSS feeds
• RDF and OWL - used to describe resources and oncerity
• SMIL - A multimedia designed to describe needles for the web

You can also practice and master it with XML instances

and XML quiz to assess your learning status