Web 2.0 Patterns and Technologies - Web Technologies (1019888BNR)

2 December 2005
Web Technologies
Web 2.0 Patterns and Technologies
Prof. Beat Signer
Department of Computer Science
Vrije Universiteit Brussel
http://www.beatsigner.com

Beat Signer - Department of Computer Science - bsigner@vub.ac.be 2December 2, 2016
Web 2.0
 The term Web 2.0 was
introduced by Tim O'Reilly
at the Web 2.0 conference
in 2004 to describe a new
generation of web apps
 user-generated content
 data as a driving force
- infoware rather than simply software
 collective intelligence via social resource and knowledge sharing
 the Web as a platform for software applications
 Not a new technology but a change in how developers
and users build applications on the Web
 user-generated content already existed earlier (e.g. Amazon)
[http://en.wikipedia.org/wiki/File:Web_2.0_Map.svg]

Main Web 2.0 Ingredients
 Social Web
 end user as a participant and content creator
 democracy
 Rich Internet Applications (RIAs)
 bring the desktop to the browser
 highly interactive applications (e.g. with drag and drop)
 based on AJAX, Flash, etc.
 Service Oriented Architectures (SOAs)
 enable the sharing of information and services between different
Web 2.0 applications
 Web Services, RSS, mashups, etc.

Web 2.0 Interaction
Service-oriented
Architecture (SOA)
information access
content creation
user-to-user
interaction
Web
collective intelligence

Web 1.0 vs. Web 2.0
Web 1.0 Web 2.0
publishing participation
reading reading and writing (participatory Web)
content management systems wikis
personal homepages blogs
simple request/response interaction Rich Internet Application (RIA)
screen scraping (extract data from HTML) service-oriented architectures
taxonomies (classification) folksonomies (tagging)
companies communities
single user social networks
bookmarking collaborative tagging / social bookmarking
... ...

Web 2.0 and the Long Tail
 The term long tail has
been introduced by Chris
Anderson in 2004
 article about Amazon etc.
- 'Touching the Void' and
'Into Thin Air' example
 Main observations
 the tail is longer than expected and now economically within reach
 the niches form a significant market when aggregated
 new economic model: combine infinite shelf space with shared
real-time public opinions and buying trends
 Major part of Internet content made up by small sites
 provide tools to address the long tail and not just the head
Joe Simpson, 1988 Jon Krakauer, 1997

Video: The Machine is Us/ing Us

Web 2.0 Examples
 Wikis
 Blogs
 Media sharing sites
 Folksonomies
 Social networking sites
 Web-based communities
 Mashups
 Web applications
 ...

Wikis
 The first wiki was the
WikiWikiWeb in 1995
 Ward Cunningham
 inspired by HyperCard
 Any user can create new
wiki pages or edit existing
pages
 no special software required on the client side (only a browser)
 Democracy-based control of the content
 revision history, discussion, ...
 Various wiki software
 MediaWiki, DokuWiki, ...

Wikipedia
 Open authoring model
 registered and anonymous
users may contribute
 some users (editors)
have special rights
 Each article has
 a history page showing
all of its changes
 a discussion page
 Issues
 reliability never guaranteed since no central authority
 vandalism
 ...

Blogs
 A blog (weblog) is a
chronologically ordered
list of information
 personal diary
 specific subjects
- e.g. celebrities
 Tool for delivering news
and getting in touch with a large community of users
 nowadays often used as a powerful channel in politics
 much harder to control than print or broadcasting media
 Popular blogs often generate revenue by advertising
 access to content is often free

Flickr
 Image hosting and sharing
website
 Image repository that is
often used by bloggers
 Managing images
 collaborative tagging
- user-generated taxonomy (folksonomy)
- one of the first websites that implemented tag clouds
 grouping in sets, collections and higher order collections
- note that an image may be added to multiple sets
 Offers a powerful Web Service API
 can easily be integrated with third-party applications

Folksonomies
 Folksonomy = 'folk' +
'taxonomy'
 user-generated taxonomy
 Social tagging
 collaboratively creating and
managing tags
 bottom up approach
- no fixed terminology
 Applications
 Annotea: shared Web annotations and bookmarks
 Delicious: social bookmarking web service
 Tag cloud visualisation

Facebook
 Social networking site
 Connect to friends and
share information
 info about current status
 post messages on a user's
public wall
 send individual messages
 share photos
 Easy to add individual applications
 Copyright issues
 what happens with content that has been uploaded to Facebook?
 Privacy issues

Twitter
 Micro-blogging and social
networking service
 Small messages (tweets)
can be posted to a user
profile
 often added via SMS
 reach millions of users from
any place around the world
within seconds
- used in protests and politics, emergencies, ...
 Can we get too connected?

Instagram
 Mobile photo and video
sharing
 'instant camera' and 'telegram'
 Simple digital filters can
be applied
 Uses hashtags to dis-
cover photos
 Users can like and com-
ment on photos as well as
follow other users

Second Life
 Virtual 3-dimensional
world by Linden Lab
 special client software
 User represented by
an avatar
 Linden dollar (L$) as a
currency
 buy land
 buy and sell goods and services to other users
 Applications
 education, business meetings, arts, ...

Academia.edu
 Social networking website
for researchers
 Sharing and rating of
resources
 research papers, conference
presentations, CVs, etc.
 Find researchers with similar research interests
 Other professional social networking websites
 LinkedIn, Xing, ...
 How to deal with profile information on different sites?
 open standards for social networking

SlideShare
 Social networking website
to share presentations
 High quality educational
material
 Various APIs for inte-
gration with other social
networking websites
 Content may spread virally through social networks
and blogs

Delicious
 Social bookmarking
service
 store bookmarks and access
them from different browsers
 share and discover book-
marks
 Non-hierarchical classi-
fication based on tags
 Offers various APIs to access the bookmarks

Mashups
 Combine content or func-
tionality from existing web-
sites, web services and
RSS feeds
 Various mashup tools
 Yahoo Pipes, IBM Mashup
Center, ...
 e.g. for developers vs. end users
 Mashup example
 composition of Google Maps and realtime information about the
position of airplanes
- http://www.flightradar24.com

Google Docs
 Free web-based office
tools
 word processor, spreadsheet
application, ...
 Mobile access via mobile
phone
 Software as a service (SaaS)
 Data safety and privacy issues

Google AdSense
 Highly customised delivery
of advertisements
 shows advertisements delive-
red via Google AdWords
 New models for payment
 pay-per-click in addition to
pay-per-impression
 Any website owner can enroll
 sometimes very complementary information
- e.g. blog with reviews about specific products together with Google
advertisements for these products

Video: The Kindness of Strangers

Social Implications of Web 2.0
 Data ownership and copyright issues
 Collective intelligence (wisdom of crowds)
 Shift of power from controlled media to
collaborative communities
 New models for crediting an individual's
content that is accessed by other users or
composed in mashup applications
 Everybody has a (big) voice
 e.g. reach millions of users within seconds via Twitter

Common Web 2.0 Patterns
 The presented Web 2.0 applications have some common
underlying patterns
 service oriented architectures (SOAs)
 software as a service
 asynchronous partial updates
 mashups
 self-organising communities
 collaborative tagging
 viral marketing
 ...

The Programmable Web
 Based on HTTP
 Data often encoded in XML
 Potential alternative data formats
 HTML
 plain text
 JavaScript Object Notation (JSON)
 binary formats

Rich Internet Applications (RIAs)
 Bring the desktop to the browser
 Highly responsive (good performance)
 asynchronous and partial content updates
 Rich Graphical User Interface (GUI)
 various RIA toolkits and environments introduced earlier
- Adobe Flash, Apache Flex and AIR
- Microsoft Silverlight
- Sun JavaFX
- JavaServer Faces (JSF)
- Mozilla XUL (XML User Interface Language)
- ...

Asynchronous Partial Updates
Client Server
 Rather than updating an entire resource (e.g. webpage),
we can asynchronously update parts of a resource
 Updates initiated by the client (or the server) based on
user interaction, state change, timeout, …
Service Service

Asynchronous Partial Updates …
 Updates cannot be initiated by the server if HTTP is used!
 have to use polling or long polling (e.g. Comet model)
 There are different possibilities how the partial update of
resources can be realised over the Web
 AJAX
 Action Message Format (AMF)
- used by Apache Flex
 REST-based implementations
 …

AJAX
 Asynchronous JavaScript and XML
 AJAX is not a technology by itself but a group
of existing technologies (term coined in 2005)
 HTML and CSS for the visualisation
 JavaScript in combination with DOM to dynamically change the
presented information and process messages on the client side
 method to asynchronously exchange data between the client
(browser) and the server
- often via the XMLHttpRequest (XHR) JavaScript object
- data can be in different formats including XML, plain text, JavaScript Object
Notation (JSON), ...
 client-side AJAX engine deals with asynchronous message
handling

XMLHttpRequest Object
 The XMLHttpRequest (XHR) object has several
important properties
 onreadystatechange
- registers a JavaScript function that will handle the response from the server
 readyState
- represents a response status from the server
• 0 (unititialised): object has been created but is uninitialised
• 1 (open): object has been created but send method not yet called
• 2 (sent): send method has been called and the HTTP response headers have been received
• 3 (receiving): some data (body) has been received but response not yet available
• 4 (loaded): all data has been received and the response is available
- a function registered via onreadystatechage is executed each time readyState changes
 responseText, responseBody and responseXML
- contains the server's response in different formats

AJAX Example
<html>
<body>
<script type="text/javascript">
function createXMLHttpRequest() {
if (typeof XMLHttpRequest != "undefined") {
return new XMLHttpRequest();
}
else if (typeof ActiveXObject != "undefined") { // code for IE5 and IE6
return new ActiveXObject("Microsoft.XMLHTTP");
}
else {
throw new Error("XMLHttpRequest object not supported!")
}
}
function getTime() {
xhr = createXMLHttpRequest();
xhr.onreadystatechange=function() {
if (xhr.readyState == 4 && xhr.status == 200) {
document.testForm.time.value=xhr.responseText;
}
}
xhr.open("GET","time.php",true);
xhr.send(null);
}
</script>

AJAX Example ...
 createXMLHttpRequest() deals with different browser
versions
 For more advanced AJAX examples see
 http://www.w3schools.com/Ajax/
 Getting Started with Ajax
 http://refcardz.dzone.com/refcardz/
getting-started-ajax
<form name="testForm">
Input: <input type="text" name="input" onkeyup="getTime();" />
Time: <input type="text" name="time" />
</form>
</body>
</html>

Google Search (Suggest) AJAX Example

AJAX
 Advantages
 reduced load time and higher responsiveness
 application state can be maintained across multiple pages since
the main container page is not reloaded
 Disadvantages
 not possible to bookmark any particular state of an application
 content may not be crawled by certain search engines since they
do not execute JavaScript code
 cannot be used in browsers with disabled JavaScript functionality
 Various libraries simplify the AJAX development
 e.g. the jQuery JavaScript library
 Web Socket API might also be used for asynchronous
updates

Service-Oriented Architecture (SOA)
 Architecture that modularises functionality as
interoperable services
 loose coupling of services
 service encapsulation
 interoperability between different operating systems and
programming languages
 mashup of services
 ...
 Software as a service (SaaS)
 software is offered as a service and may itself be a composition of
third-party services

Representational State Transfer (REST)
 REST is an architectural style for distributed hypermedia
systems requirering the following constraints
(1) separation of concerns between client and server
 client and server can be developed and replaced independently
(2) uniform interface
 identification of resources (e.g. URIs on the Web)
 manipulation of resources on the server via representation on the client side
 self-describing messages (e.g. MIME type on the Web)
 hypermedia for application state change (e.g. hypertext links to related
resources)
(3) stateless
 no client state is stored on the server side
(4) cacheability
 responses must explicitly or implicitly define whether they are cacheable

Representational State Transfer (REST) ...
(5) layering
 intermediary servers (proxies) can be transparently added between the client
and the server
(6) code on demand (optional)
 the server can send application logic (code) to the client (e.g. Java Applets)
 A service that conforms at least to the first five
constraints is called a RESTful service
 The Web is an implementation of a system conforming to
the REST architectural style
 however, RESTful services can also be implemented over
protocols other than HTTP

Web Services
 Web-based client-server communication
over HTTP
 Two main types of Web Services
 Big Web Services
- Universal Description, Discovery and Integration (UDDI)
- Web Services Description Language (WSDL)
- Simple Object Access Protocol (SOAP)
 RESTful Web Services
- better integrated with HTTP and web browsers
- makes use of GET, POST, PUT and DELETE HTTP methods

Big Web Services
Service
Provider
Service
Requester
Service
Broker
UDDI
WSDL
SOAP
SOAP
WSDL

Big Web Services ...
 Universal Description, Discovery and Integration (UDDI)
 yellow pages for WSDL
 "global" registry describing available business services
 very complex
 Microsoft and IBM shut down their public UDDI registries in 2006
 Web Service Description Language (WSDL)
 XML application to describe a Web Service's functionality
 complex
 Simple Object Access Protocol (SOAP)
 defines an envelope for transporting XML messages
 The Web Service Stack contains many other protocols
 BPEL, WS-Security, WS-Reliability, WS-Transaction, ...

SOAP
 Successor of XML-RPC (discussed earlier)
 Introduced in 1998 as Simple Object Access Protocol
 Dave Winer, Don Box, Bob Atkinson and Mohsen Al-Ghosein
 since version 1.2 the name is no longer treated as an acronym
 XML-based communication protocol
 A SOAP message consists of an <Envelope> element
which contains
 an optional <Header> element
 a <Body> element
- remote procedure call or response information
 SOAP requests are often sent via HTTP POST requests

SOAP Request Message Example
 predefined SOAP attributes
- encodingStyle: defines the used data types
- mustUnderstand: if set to 1 then the server has to understand the header
- actor: can be used to delegate the header to an intermediary receiver (proxy)
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
<soap:Header>
<t:username xmlns:t="http://wise.vub.ac.be/transaction/"
soap:mustUnderstand="1">pellens</t:username>
</soap:Header>
<soap:Body xmlns:c="http://wise.vub.ac.be/courses/">
<c:getCourseInfo>
<c:courseID>4011474FNR</c:courseID>
</c:getCourseInfo>
</soap:Body>
</soap:Envelope>

SOAP Response Message Example
 note that also a response message can have a <Header> element
 the body contains a <Fault> element if something went wrong on
the server side
<soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
<soap:Body>
<c:getCourseInfoResponse xmlns:c="http://wise.vub.ac.be/courses">
<c:title>Web Information Systems</c:title>
<c:description>The goal of this course is to teach students the concepts and
technologies for realising Web Information Systems (WIS). This ranges from basic
network technologies and protocols to high level frameworks for the design and
...
</c:description>
</c:getCourseInfoResponse>
</soap:Body>
</soap:Envelope>

SOAP ...
 Advantages
 platform and language independent
 SOAP over HTTP results in less problems with proxies and
firewalls than other remote procedure call solutions (e.g. CORBA)
 there exist a lot of tools and language bindings that automatically
create the required client and server-side functionality
- e.g. Java API for XML Web Services (JAX-WS)
 Disadvantages
 slower than non-verbose protocols (e.g. CORBA)
 Big Web Services are not simple
 HTTP is reduced to a simple transport protocol for a large amount
of XML metadata payload
- does not make use of the rich functionality offered for HTTP envelopes
 no mechanism for the caching of results

RESTful Web Services
 A RESTful web service (or RESTful Web API) is a simple
web service implemented using HTTP
 The definition of RESTful web service includes
 the URI of the web service (e.g. http://wise.vub.be/course/)
- different resources identified by unique URIs
 the type (MIME) of data supported by the service
- e.g. application/json, application/xml, ...
 supported set of operations via HTTP methods
- e.g. GET, POST, PUT, DELETE
 One-to-one mapping between create, read, update, and
delete (CRUD) operations and HTTP methods
 POST (create), GET (read), PUT (update) and DELETE (delete)

RESTful Web Service Example
POST /users HTTP/1.1
Host: wise.vub.ac.be
Content-Type: application/xml
<user>
<name>Roels</name>
</user> create
GET /users/Roels HTTP/1.1
Accept: application/xml read
PUT /users/Roels HTTP/1.1
Content-Type: application/xml
<user>
<name>Signer</name>
</user> update
DELETE /users/Signer HTTP/1.1
Accept: application/xml delete

Really Simple Syndication (RSS)
 Format that is used to read and write frequently updated
information on the Web
 e.g. blog entries
 specific channels on news sites
 ...
 Special RSS readers or aggregators
 Two main RSS variants
 simple fork (Dave Winer)
- RSS 0.92, RSS 0.93, RSS 0.94 and RSS 2.0
 RDF fork
- RSS 1.0
 RSS feeds are represented as XML documents

RSS Example
 many other elements
 <language>, <copyright>, <pubDate>, ...
<?xml version="1.0" encoding="ISO-8859-1" ?>
<rss version="2.0">
<channel>
<title>W3Schools Home Page</title>
<link>http://www.w3schools.com</link>
<description>Free web building tutorials</description>
<item>
<title>RSS Tutorial</title>
<link>http://www.w3schools.com/rss</link>
<description>New RSS tutorial on W3Schools</description>
</item>
<item>
<title>XML Tutorial</title>
<link>http://www.w3schools.com/xml</link>
<description>New XML tutorial on W3Schools</description>
</item>
...
</channel>
...
</rss>

Atom
 Two related standards
 Atom Syndication Format
- similar to RSS
- supports more content formats (e.g. videos) than RSS
 Atom Publishing Protocol (APP)
- HTTP-based approach for creating and editing Web resources
- similar to the RESTful web service example shown earlier
 Many web service interfaces are based on
the Atom protocol
 Microsoft Windows Live
 OpenSocial
 …

Homework
 Watch the video 'The Kindness of Strangers'
 http://www.ted.com/talks/lang/eng/jonathan_zittrain_the_web_is_
a_random_act_of_kindness.html

Exercise 8
 AJAX and Google Maps

References
 James Governor et al., Web 2.0 Architectures,
O'Reilly Media, May 2009
 Chris Anderson, The Long Tail, Wired 12(10), 2004
 http://www.wired.com/wired/archive/12.10/tail.html
 Michael Wesch, The Machine is Us/ing Us
 http://www.youtube.com/watch?v=NLlGopyXT_g
 Jonathan Zittrain, The Kindness of Strangers,
TEDGlobal 2009, Oxford, UK, July 2009
 http://www.ted.com/talks/lang/eng/jonathan_zittrain_the_web_is_
a_random_act_of_kindness.html
 Live Flight Tracker
 http://www.flightradar24.com

References
 James Surowiecki, The Wisdom of Crowds,
Anchor, August 2005

2 December 2005
Next Lecture
Semantic Web and Web 3.0

Web 2.0 Patterns and Technologies - Web Technologies (1019888BNR)

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