HTML5 notes (1)-HTML5 Definition

Preface

HTMl5 has become increasingly popular since last year. I also pay attention to and learn something from time to time. I made some notes and made some thoughts in this process. Therefore, I have noted down some technical background that is "objective, it is more about your own "subjective" views, hoping to further communicate with other learners, and hope to have a higher level of understanding in the future.

What is HTML?

When I look at the introduction of a new technology, I like to read articles that follow the logic of "what is it" and "what is it not. But I am not capable of writing this...

HTML is first a set of specifications and definitions developed by W3C, rather than specific implementations. Just like TCP/IP is a set of protocols, and there are many implementations of TCP/IP protocols in the world: You can use C/C ++ to implement it, it can also be implemented in other languages such as Java. A browser is the most common application that implements and supports HTML, but it is neither unique (Other widgets such as Yahoo ), it not only includes HTML (such as plug-ins and various extensions ). HTML often does not appear independently. The most popular technology nowadays is HTML + CSS + JavaScrip + AJAX.

HTML provides a technology that allows web programmers around the world to write web pages in a unified syntax specification, it presents text, graphics, animations, sounds, tables, links, and other content as a carrier to bring a unified Internet experience to Internet users.

Currently, most of the popular web pages in the world are written in html4. HTML5 is an upgraded version of the former. HTML5 was not identified from the very beginning. In the earlier W3C XHTML Working Group, they wanted to use XHTML 2.0 with more strict semantics and syntax, and it was also a radical version of thorough refactoring, to replace HTML4, but this plan was blocked internally. Even Tim Berners-Lee, the author of the Internet and W3C, publicly posted a blog post to express their different views, so HTML5 was later supported as orthodox.

HTML5 includes the content

Most of the time we mention HTML5, the meaning may not be exactly the same. I use my own words to express HTML5 in a narrow sense and HTML5 in a broad sense.

In a narrow sense, HTML5 often refers to HTML itself, or even only to XML-based HTML tags and their related syntax. If you take some training courses, you will find that this is the content and example that the teacher has been teaching most of the time. HTML5 is the biggest highlight of HTML4 in the following aspects:

1. Added support for labels such as Canvas, Video, and Audio, and enhanced the display capabilities of multimedia, painting, and even animation.
2. Added some more semantic labels or interfaces, such as aside, header, and footer.
3. Modified or discarded some HTML tags and semantics, such as the form features, Marquee, and frameset.
4. We recommend that you move the color, size, and alignment typographical attributes to CSS. HTML5 is mainly responsible for the layout of webpages.

In a broad sense, HTML5 includes the front-end technology of Web pages, namely, HTML5 + CSS3 + JavaScript + Web Application API in a narrow sense, and may also support SVG and plug-ins. Among them, the Web Application API includes some of the most important and exciting features of HTML5 (since it is an API interface, it indicates that this is only a set of standard definitions, and each browser has different implementations):

1. Server-Sent Events: Message Events initiated by the Server (for the time being, translate them...) to easily implement updates initiated by the Server, similar to the Push mechanism. Note that it is unidirectional.
2. Web SQL Database: the client can save data in the local Database in the form of SQL (somehow the Web Application workgroup says they are not maintaining this part of the document)
3. Web Sockets: the client can use the WebSocket protocol to communicate with the host in two directions, which is more powerful, efficient, and reduces traffic than XmlHttpRequest.
4. Web Storage: The local Storage capability of the client, including Session-related (such as the status of webpage orders) and global data (such as map data and game level information)
5. Web Workers: allows the client side to run some time-consuming pure computing operations in a thread-like manner in a non-UI thread like other advanced programming languages such as C ++, and uses the Message mechanism for communication.

About Web Application API

This is my personal opinion: the prototype of Web Application API actually exists in the HTML4 era, yahoo, Apple, and other companies define some extended interfaces based on different platforms in their respective Widget specifications. The purpose is to upgrade websites to applications, it is compatible with W3C HTML specifications and has some features of Native apps. It is as easy to deploy and seamlessly upgraded as HTML web pages, it also has powerful features of local applications.

This is also the main purpose of developing Web Application APIs: both cross-platform and powerful features.

Web Application APIs may also be part of the HTML5 specification. However, during the compilation process, the developers found that they would make HTML5 very large. In addition, these features are relatively independent, they can be defined as interfaces rather than syntaxes, so they are written in a unified set of Web Application 1.0. Therefore, they are not part of HTML5 strictly.

Therefore, from this perspective, HTML5 is actually not a brand new technology, but HTML5 is actually "extended HTML4 + several standard encapsulated operating system interfaces ".

Summary

Therefore, in my opinion, HTML, as a set of standards and norms independent from the platform, has contributed the greatest part in its cross-platform support from major vendors in the development process, this allows Internet users around the world to gain a relatively unified Internet experience without having to worry about the technical details behind it. At a higher level, it is like a unified voltage, unit standard, or even a unified economic and political system in the real world. People all over the world are based on this platform, in order to achieve the flattening of knowledge and the regionalization of communication.