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The Web and HTTP-based Systems

HTTP and The Web_122221A
[HTTP and The Web - Mozilla]


    - Web Components

    Web Components is a set of features that provides a standard component model for the Web, allowing individual HTML elements to be encapsulated and interoperated. The main techniques used to create them include:

    • Custom Elements: API for defining new HTML elements
    • Shadow DOM: Encapsulated DOM and styles, with composition
    • HTML templates: HTML fragments that are not rendered but stored until instantiated via JavaScrip


    - Hypertext Transfer Protocol (HTTP) 

    The Hypertext Transfer Protocol (HTTP) is an application-layer protocol in the Internet Protocol Family model for distributed, collaborative, hypermedia information systems. HTTP is the basis for data communication on the World Wide Web, where hypertext documents include hyperlinks to other resources that users can easily access, such as by clicking a mouse or tapping the screen in a Web browser.

    HTTP (Hypertext Transfer Protocol) is a set of rules for transferring files such as text, images, sound, video, and other multimedia files over a network. Once users open their web browsers, they are using HTTP indirectly. HTTP is an application protocol that runs on top of the TCP/IP protocol suite, which forms the basis of the Internet. 


    - Hypertext Markup Language (HTML)

    Hypertext Markup Language, or HTML, is a standard markup language designed for documents displayed in web browsers. It is often aided by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript. 

    Hypertext Markup Language (HTML) is the most basic building block of the Web. It defines the meaning and structure of web content. Technologies other than HTML are often used to describe the appearance/presentation (CSS) or functionality/behavior (JavaScript) of web pages.

    "Hypertext" refers to the links that connect web pages to each other within a single website or between websites. Links are a fundamental aspect of the web. By uploading content to the Internet and linking it to pages created by others, you become an active participant on the World Wide Web.

    A web browser receives an HTML document from a web server or local storage and renders the document as a multimedia web page. HTML semantically describes the structure of a web page and initially included hints of its appearance.

    HTML uses "tags" to annotate text, images, and other content for display in a web browser. HTML tags include special "elements" such as <head>, <title>, <body>, <header>, <footer>, <article>, <section>, <p>, <div>, <span>, <img>, <aside>, <audio>, <canvas>, <datalist>, <details>, <embed>, <nav>, <output>, <progress>, <video>, <ul>, <ol > , <li> and so on.

    HTML elements are separated from other text in the document by "tags," which consist of the element name surrounded by "<" and ">". The names of elements within tags are case-insensitive. That is, it can be written in uppercase, lowercase, or a mixture. For example, the <title> tag could be written as <Title>, <TITLE>, or any other way. However, the convention and recommended practice is to write labels in lowercase.

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    - Cascading Style Sheets (CSS) 

    Cascading Style Sheets (CSS) is a style sheet language used to describe the presentation of documents written in markup languages such as HTML or XML (including XML dialects such as SVG, MathML, or XHTML). CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript. 

    CSS aims to achieve a separation of content and presentation, including layout, colors, and fonts. This separation improves content accessibility; provides more flexibility and control in the specification of presentation features; enables multiple web pages to share formatting by specifying related CSS in separate .css files, which reduces complexity and repetition of structural content; and enabling .css files to be cached to improve page load speed among pages sharing that file and its formatting. 

    The separation of format and content also allows the same markup page to be rendered in different styles for different rendering methods, such as on-screen, in print, by speech (via a speech-based browser or screen reader), and Braille-based Haptic devices. CSS also has rules for alternate formatting if the content is accessed on a mobile device. 

    Name concatenation comes from a specified precedence scheme to determine which style rule to apply if more than one rule matches a particular element. This cascading priority scheme is predictable. 

    The CSS specification is maintained by the World Wide Web Consortium (W3C). The Internet media type (MIME type) text/css has been registered for use with CSS by RFC 2318 (March 1998). W3C provides a free CSS Validation service for CSS documents. 

    In addition to HTML, other markup languages support the use of CSS, including XHTML, plain XML, SVG, and XUL. 


    - JavaScript

    JavaScript, often abbreviated to JS, is a programming language that ranks alongside HTML and CSS as one of the core technologies of the World Wide Web. By 2022, 98% of websites will use JavaScript on the client side for page behavior, often in combination with third-party libraries. All major web browsers have a dedicated JavaScript engine to execute code on the user's device. 

    JavaScript is a high-level, often just-in-time compiled language that conforms to the ECMAScript standard. It has dynamic typing, prototype-based object orientation, and first-class functionality. It is multi-paradigm, supporting event-driven, functional, and imperative programming styles. It has application programming interfaces (APIs) for manipulating text, dates, regular expressions, standard data structures, and the Document Object Model (DOM). 

    The ECMAScript standard does not include any input/output (I/O), such as networking, storage, or graphics facilities. In fact, a web browser or other runtime system provides a JavaScript API for I/O. 

    JavaScript engines were originally used only in web browsers, but are now a core component of some servers and various applications. The most popular runtime system for this usage is Node.js. 

    Although Java and JavaScript are similar in name, syntax, and their respective standard libraries, the two languages are distinct and differ significantly in design. 


    - Web APIs

    A Web API is an application programming interface (API) for a web server or web browser. As a web development concept, it may relate to the client side of a web application, including whatever web framework is in use. A server-side web API consists of one or more endpoints exposed publicly to a defined request-response messaging system, usually expressed in JSON or XML via an HTTP-based web server. Server API (SAPI) is not considered a server-side web API unless it is publicly accessible by a remote web application. 



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