HTML5 and the Open Web Platform - Lecture 03 - Web Information Systems (WE-DINF-11912)

2 December 2005
Web Information Systems
HTML5 and the Open Web Platform
Prof. Beat Signer
Department of Computer Science
Vrije Universiteit Brussel
http://www.beatsigner.com

October 10, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 2
Hypertext Markup Language (HTML)
 HTML is an application of the Standard Generalized
Markup Language (SGML)
 simple human-readable markup language with a number of
markup tags that can be manipulated by any text editor
 Various markup tags to define the structure and
presentation of a HTML document (webpage)
 root element (<html>), header (<head>), body (<body>) and
title (<title>)
 headings (<h1>, ... <h6>) and paragraphs (<p>)
 tables (<table>, <tr> and <td>) and lists (<ol>, <ul> and <li>)
 images (<img>)
 ...

Hypertext Markup Language (HTML) ...
 HTML documents are transformed into a Document
Object Model (DOM) by the browser
 tree of elements (and attributes) with textual content
 HTML DOM defines objects and properties for HTML elements
- document node, element nodes, text nodes, attribute nodes
and comment nodes
 standard to create, read, update and delete HTML elements
 Hyperlinks to connect different HTML documents
 anchor tag (<a href="...">)
 only embedded hyperlinks are supported

HTML Example
<!DOCTYPE html
PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Vrije Universiteit Brussel</title>
</head>
<body>
<h1>News</h1>
<p>Internationalisation was this years theme of the academic opening of
the <a href="http://www.vub.ac.be">Vrije Universiteit Brussel</a>.
</p>
<p>The Vrije Universiteit Brussel will organise the new International
Business Arbitration post-graduate course from the new academic year
onwards.<img src="course.jpg" width="120" height="100" alt="Course">
</p>
...
</body>
</html>

HTML DOM Example
News
html
head body
document
title
Vrije Univer ...
h1 p p …
…
Internationa ... a
Vrije Uni ...
href
http:// ...
document node
element node
attribute node
text node
root node

History of HTML
 HTML 1.0 (1993)
 HTML 2.0 (1995)
 at that time the Netscape Navigator offered much more
functionality than the HTML standard
- "browser war" between Netscape and Internet Explorer
 HTML 3.2 (1997)
 first version that was developed exclusively by the Word Wide
Web Consortium (W3C)
 introduced tables
 introduced a lot of new elements for the visual appearance of a
document (that was not the original idea of HTML!)
- e.g. <font> element or color attribute
- most elements now deprecated and cascading style sheets should be used

History of HTML ...
 HTML 4.0 (1997) and HTML 4.01 (1999)
 internationalisation (Unicode)
 introduction of Cascading Style Sheets (CSS)
 In 1998 the W3C decided to not further evolve HTML!
 XHTML 1 (2000) and XHTML 1.1 (2001)
 XML version of HTML (draconian error handling)
 XHTML 2.0 (never finished, discontinued in 2009)
 revolutionary changes  breaking backwards compatibility
 Web Hypertext Application Technology Working Group
(WHATWG) founded in 2004 (led by Ian Hickson)
 Web Forms 2.0 and Web Applications 1.0  HTML5

History of HTML ...
 In 2006 the W3C decided to work on HTML again
 based on WHATWG's Web Applications specification
 HTML5 specification is currently developed
simultaneously by the WHATWG and the W3C
HTML Working Group
 HTML – Living Standard, WHATWG
 HTML5 – A Vocabulary and Associated APIs for HTML and
XHTML, W3C Working Draft
 Roadmap
 HTML5 Proposed Recommendation on September 16, 2014
 HTML5 W3C Recommendation predicted for the end of 2014
(originally 2022)

HTML5
... HTML5 does not belong to a company or a specific
browser. It has been forged by a community of people
interested in evolving the web and a consortium of
technological leaders that includes Google, Microsoft, Apple,
Mozilla, Facebook, IBM, HP, Adobe, and many others. The
community and consortium continue to collaborate on
universal browser standards to push web capabilities even
further. The next generation of web apps can run high-performance
graphics, work offline, store a large amount of
data on the client, perform calculations fast, and take
interactivity and collaboration to the next level. ...
Why HTML5 Rocks, http://www.html5rocks.com

HTML5 Design Principles
 Compatibility
 evolve the language for easier authoring of web applications
 Utility
 solve real problems (pragmatic approach)
 separation of content and presentation (CSS)
 Interoperability
 interoperable browser behaviour
 identical error handling across browsers resulting in the same
DOM tree for broken HTML
 Universal Access
 features should preferably work across different platforms
(cross-platform), devices and media
 design features should be accessible to users with disabilities

HTML5 Design Principles ...
 Simple is better
 new doctype: <!DOCTYPE html>
 HTML5 APIs
 ...
 Avoid external plug-ins
 plug-ins are often not nicely integrated with HTML documents
 plug-ins can be disabled or blocked (e.g. Adobe Flash on iPad)
 plug-ins may crash
 ...

HTML5 and Open Web Platform APIs
Sergey Mavrody, January 2013

Current HTML5 Browser Support
When can I use..., http://caniuse.com/#cats=HTML5

JavaScript/ECMAScript
 Growing use of JavaScript frameworks and AJAX
 JavaScript engine race
 in 2006 Adobe donated their just-in-time (JIT) compilation engine
and ECMAScript virtual machine to the Mozilla project
 healthy competition among browser vendors
- bring JavaScript performance closer to that of native desktop application code
Black Duck, 2011 http://www.whatbrowser.org

Browser Performance

Web Browsers (1990–2013)
WorldWideWeb
Internet Explorer
Trident Engine
Mozilla
Firefox
WebKit Engine
Opera
Presto Engine
Opera Mini
Chrome
Safari
Gecko Engine
http://en.wikipedia.org/wiki/File:Timeline_of_web_browsers.svg

HTML Markup
 Some elements have been added
 structural elements such as <article>, <section>, <header>,
<footer> or <nav>
 media elements including <video>, <audio> or <embed>
 a <canvas> drawing element
 Other elements have been removed
 <big>, <font>, <strike>, <u>, <center>, ...
 New form functionality (originally Web Forms 2.0)
 form elements such as <datalist> or <output>
 input types such as date, color, email, tel, range, ...
 native functionality for client-side validation (no scripting)
W3C Proposed Recommendation

Forms Example

Forms Example ...
<!DOCTYPE html>
<html>
<body>
<form action="submit.html">
Name (required) <input type="text" name="name" required autofocus>
Title <input type="text" name="title">
Shoesize <input list="range" min="10" max="30" name="shoesize">
Email (required) <input type="email" name="mail" required>
Webpage <input type="url" name="webpage">
Date of Birth <input type="date" name="birthday">
<input type="submit">
</form>
</body>
</html>

Video
 <video> element can be used to play videos
in HTML pages
 element has methods, properties and events
 no external plug-in (e.g. Adobe Flash) is required
 e.g. an HTML5 YouTube version (working without Flash) is
available at http://www.youtube.com/html5
 No single video format is supported by all browsers
 MP4, WebM and Ogg
<video width="640" height="480" controls="controls">
<source src="bullhead.mp4" type="video/mp4" />
<source src="bullhead.webm" type="video/webm" />
The video tag is not supported by your browser!
</video>

Video ...
 Current limitations
 no adaptive streaming
 no copy protection
 limited access to web cams and microphones but this is going to
change in the near future (via the Media Captue API)
 HTML5 Video vs. Adobe Flash
... Our future work with Flash on mobile devices will be focused on
enabling Flash developers to package native apps with Adobe AIR for all
the major app stores. We will no longer continue to develop Flash Player
in the browser to work with new mobile device configurations (chipset,
browser, OS version, etc.) following the upcoming release of Flash
Player 11.1 for Android and BlackBerry PlayBook. ...
Adobe Systems Incorporated, November 9, 2011

Video Support
When can I use..., http://caniuse.com/#feat=video

MP4 Support
 MPEG 4 files with H264 video codec and AAC audio codec
When can I use..., http://caniuse.com/#feat=mpeg4

WebM Support
 WebM files with VP8 video codec and Vorbis audio codec
When can I use..., http://caniuse.com/#feat=webm

Ogg Support
When can I use..., http://caniuse.com/#feat=ogv
 Ogg files with Theora video codec and Vorbis audio codec

Canvas 2D
 <canvas> tag can be used in combination with
JavaScript to draw on a webpage (raster graphics)
 define a canvas with an id and use it in the JavaScript code
 draw lines, shapes (with optional gradient filling) etc. or add text
<canvas id="drawingArea" width="200" height="200">
The canvas tag is not supported by your browser!
</canvas>
<script type="text/javascript">
var canvas = document.getElementById("drawingArea");
var context = canvas.getContext("2d");
context.fillStyle = "#0000FF";
context.fillRect(50,50,100,50);
context.moveTo(0,0);
context.lineTo(200,200);
context.stroke();
</script>

HTML5 Canvas and JavaScript Demo
http://www.youtube.com/watch?v=cnexWE5Rbx4

Canvas 2D Support
When can I use..., http://caniuse.com/#feat=canvas

Scalable Vector Graphics (SVG)
 Vector graphics alternative to Canvas 2D
 resolution independent
 define graphics in XML format (embeddable in HTML)
 good support for animations (declarative description)
 full control over each element via the SVG DOM API
 On the other hand, Canvas 2D offers better performance
W3C Recommendation
<!DOCTYPE html>
<html lang="en">
<head>...</head>
<body>
<svg xmlns="http://www.w3.org/2000/svg">
<circle id="myCircle" cx="50" cy="50" r="100" fill="blue" />
</svg>
</body>
</html>

SVG Support
When can I use..., http://caniuse.com/#cats=SVG

Web Graphics Library (WebGL)
 3D graphics API for JavaScript
 getContext("3d") might be used in the future
 currently getContext("webgl") or
getContext("experimental-webgl")
 GPU accelerated

Video: Google Body Browser (WebGL)

WebGL Support
When can I use..., http://caniuse.com/#feat=webgl

Web Storage
 localStorage and sessionStorage JavaScript
objects to store data (key/value) on the client
 localStorage has no time limit whereas sessionStorage is
deleted when the browser window is closed
- localStorage with same origin policy and sessionStorage per window
 replace cookies for large amounts of data
- cookies are limited in size (maximal 4 KB) and are sent with each request
W3C Recommendation
if (localStorage.counter) {
localStorage.counter = Number(localStorage.counter) + 1;
}
else {
localStorage.counter = 1;
}
document.write("Total of " + localStorage.counter + " visits");
</script>

Web Storage Support
When can I use..., http://caniuse.com/#search=web%20storage

Indexed Database API
 Low-level indexed storage capabilities
 other libraries to be developed based on top of the indexed core
 In contrast to the Web Storage API, an object store may
have an arbitrary number of indexes
 No space limit such as in the Web Storage API
 Likely going to become the future structured storage
 replacing the Web SQL API (which is now deprecated)
 Introduces the concept of transactions and cursors
W3C Candidate Recommendation

Indexed Database Support
When can I use..., http://caniuse.com/#search=indexed%20data

Drag and Drop
 Drag items and drop them anywhere in the browser
 define draggable elements via the draggable attribute
 define elements that can accept drops
 exchange information via the dataTransfer object
 Items can also be drag and dropped from the browser to
external applications

Drag and Drop ...
<!DOCTYPE html>
<html>
<head>

<script>
function drag(event) {
event.dataTransfer.setData("text/plain", event.target.id);
}
function drop(event) {
event.preventDefault();
var data=event.dataTransfer.getData("text/plain");
event.target.appendChild(document.getElementById(data));
}
function allowDrop(event) {
event.preventDefault();
}
</script>
</head>
<body>
<div id="div1" ondrop="drop(event)" ondragover="allowDrop(event)">
<img src="wise.gif" draggable="true" ondragstart="drag(event)" id="d1">
</div>
<div id="div2" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
</body>
</html>

Drag and Drop Support
When can I use..., http://caniuse.com/#feat=dragndrop

Web Workers
 When executing JavaScript in an HTML page, the
page becomes non-responsive until the script is finished
 Web Workers can be used to execute JavaScript code in
a background process (thread)
 to avoid the complexity of multi-threaded programming, Web
Workers have independent JavaScript contexts and can only
interact with each other via event-driven message passing
var worker = new Worker("myScript.js");
worker.onmessage = function(event) {
alert("The worker received this: " + event.data);
...
};
worker.postMessage("Hello worker!");
</script>
W3C Candidate Recommendation

Web Workers Support
When can I use..., http://caniuse.com/#feat=webworkers

Offline Web Applications
 Application cache is used for
 offline browsing where users can use the web application while
they are offline
 increased performance due to cache hits and reduced server load
 Managed via a cache manifest (on every page)
W3C Working Group Note
<!DOCTYPE html>
<html lang="en" manifest="/myApp.appcache">...</html>
CACHE MANIFEST
CACHE:
index.html
default.js
NETWORK:
dynamic.js
FALLBACK:
time.js fallback-time.js
#version 3

Offline Web Applications Support
When can I use..., http://caniuse.com/#feat=offline-apps

Other HTML5 Features
 Note that some other important HTML5 features
are introduced later in the course
 Web Sockets
 WebRTC
 Geoloaction
 Microdata
 …

When Can We Start to Use HTML5?
 HTML5 is not yet an official standard – but many HTML5
features are already implemented by browser vendors
 line between web apps and native apps gets blurry!
 Seamless transition from HTML 4.01 to HTML5
 backwards compatibility and fallback solutions
 It is time to start using different parts of HTML5!
... In a recent online survey con-ducted
by Contemporary Analysis,
on behalf of appendTo, a JavaScript
and HTML5 consulting company,
84% of developers planned on using
HTML5 in projects within the next
6 months. ...
When can I use..., http://caniuse.com/#cats=HTML5 Contemporary Analysis, September 2011

Problems with HTML
 Mix of content, structure and presentation
 no separation of concerns
 structure of content defines the presentation in the browser
 "Forgiving" browsers weaken the standard
 an HTML document with errors (e.g. missing tags etc.) will still be
rendered without any error messages
 HTML documents can be checked against the standard
- http://validator.w3.org
 most existing websites (>99%) contain errors
- exercise: can you find a webpage without any errors?
 Lack of support for multiple presentations

Cascading Style Sheets (CSS)
 Separation of presentation and content
 visualisation of HTML elements defined by styles
 enables multiple presentations of the same content
 media-specific style sheets via the media attribute
<html>
<head>
...
<link ref="stylesheet" type="text/css" href="default.css"
media="screen, tv" />
<link rel="stylesheet" type="text/css" href="alternative.css"
media="print, handheld" />
</head>
<body>
...
</body>
</html>

CSS Syntax
 The CSS syntax contains three parts
 a selector
- HTML element
 a property and a value
- surrounded by curly braces
- multiple properties are separated with a semicolon
 Example
selector {property1:value1;propertyn:valuen}
h1 {color:red;font-size:10px}
p {color:blue}

CSS Inclusion
 There are three ways how a style sheet can be inserted
 inline style
 internal style sheet
 external style sheet
 Inline style
 defined via the style attribute of the corresponding
HTML element
 still mixes content and presentation and should therefore be
avoided whenever possible
<h1 style="color:red;font-size:10px">Urgent Tasks</h1>

CSS Inclusion ...
 Internal style sheet
 used when single document has a unique style
 defined in the <head> section
<html>
<head>
...
<style type="text/css">
h1 {color:red;font-size:10px}
p {color:blue}
...
</style>
</head>
<body>
...
</body>
</html>

CSS Inclusion ...
 External style sheet (in *.css file)
 changes to the overall appearance of an entire website can be
managed in a single file
- removes a lot of redundancy
- saves a lot of time
- leads to more consistent websites
<html>
<head>
...
<link rel="stylesheet" type="text/css" href="default.css" />
</head>
<body>
...
</body>
</html>

Multiple Style Sheets
 Multiple styles will cascade into a single one
 properties/values are inherited from more specific style sheets
 Overriding priorities
(1) default browser style
(2) external style sheet
(3) internal style sheet
(4) inline style (highest priority)
 Note that if the link to the external style sheet in the
<head> section is placed after the internal style sheet, then the
external style sheet will override the internal one

Exercise 3
 Java Servlet Technology
 develop a servlet that processes data which has
been entered in an HTML form

References
 HTML – Living Standard, WHATWG
 http://www.whatwg.org/html
 HTML5 – A Technical Specification for Web Developers
 http://developers.whatwg.org
 HTML5 – A Vocabulary and Associated APIs for HTML
and XHTML, W3C Working Draft
 http://www.w3.org/TR/html5/
 HTML Design Principles, W3C Working Draft
 http://www.w3.org/TR/html-design-principles/
 HTML Canvas 2D Context, W3C Working Draft
 http://www.w3.org/TR/2dcontext/

References ...
 Simon Sarris, HTML 5 Canvas: A Web Standard
for Dynamic Graphics (refcardz #151)
 http://refcardz.dzone.com/refcardz/html5-canvas-web-standard
 HTML5 Canvas and JavaScript Demo
 http://www.youtube.com/watch?v=cnexWE5Rbx4
 Scalable Vector Graphics (SVG) 1.1
 http://www.w3.org/TR/SVG11/
 Web Storage, W3C Candidate Recommendation
 http://www.w3.org/TR/webstorage/
 Indexed Database API, W3C Working Draft
 http://www.w3.org/TR/IndexedDB/

References ...
 Gerard Gallant, HTML5: IndexedDB,
(refcardz #195)
 http://refcardz.dzone.com/refcardz/html5-indexeddb
 Web Workers, W3C Working Draft
 http://www.w3.org/TR/workers/
 Gerard Gallant, HTML5 Web Workers: Multithreaded
JavaScript for High-Performance Web Apps
(refcardz #177)
 http://refcardz.dzone.com/refcardz/html5-web-workers
 Web Audio API, W3C Working Draft
 http://www.w3.org/TR/webaudio/

References ...
 HTML Tutorial
 http://www.w3schools.com/html/
 Andy Harris, Core HTML (refcardz #64)
 http://refcardz.dzone.com/refcardz/core-html
 James Sugrue, HTML5: The Evolution
of Web Standards (refcardz #123)
 http://refcardz.dzone.com/refcardz/html5-new-standards-
web-interactivity
 Mark Pilgrim, HTML5: Up and Running - Dive Into the
Future of Web Development, O'Reilly Media, August
2010, ISBN-13: 978-0596806026

References ...
 Cascading Style Sheets (CSS) Snapshot 2010,
W3C Working Group Note
 http://www.w3.org/TR/CSS/
 Molly E. Holzschlag, Core CSS (Part I, II & III)
(refcardz #19, #25 and #34)
 http://refcardz.dzone.com/refcardz/corecss-part1
 http://refcardz.dzone.com/refcardz/corecss2
 http://refcardz.dzone.com/refcardz/corecss3
 CSS Tutorial
 http://www.w3schools.com/css/
 Offline Web Applications, W3C Working Group Note
 http://www.w3.org/TR/offline-webapps/

References ...
 Max Firtman, HTML5 Mobile Development,
(refcardz #186)
 http://refcardz.dzone.com/refcardz/html5-mobile-development
 W3C Markup Validation Service
 http://validator.w3.org

2 December 2005
Next Lecture
XML and XML Applications

HTML5 and the Open Web Platform - Lecture 03 - Web Information Systems (WE-DINF-11912)

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