Transcript - Muhazam
EEC4113 Data Communication & Multimedia System Chapter 12: Application Layer – Text-Based Multimedia by Muhazam Mustapha and contributions by class members, October 2010 Learning Outcome • At the end of this chapter, the students are expected to have the knowledge about – Type Declaration: File Formats, Headers, MIME – Text Data Transfer: Web Services, RSS Feed – Web 2.0 Chapter Content • Type Declaration • Text Transfer • Web 2.0 Type Declaration Text-Based Multimedia • Multimedia consists of huge files of images, video and audio • However, there are tricks that enable multimedia to be shared as text • The scheme involves transferring of links and type declarations Type Declaration • Files or data transfers that involves binary data need some way to inform the reader about its content • The scheme is called file formatting, which involves 2 parts: – Header Information – Actual Data Header Information • Also called metadata • The content of header explains the data that follows it • For example, a JPEG image file may include in its header about: – No. bits per pixel, or per color – Image horizontal and vertical dimension – Compression quality level Header Information • Data communication also involves header information • In protocols definition we often find metadata proceeding the actual data • For example, in an HTTP transfer header, we can include: – The type of data being transferred – The size of the data being transferred – The last modification date of the data, etc RIFF Type • Resource Interchange File Format • Created by Microsoft and IBM for standardizing file format definition • It starts with a text tag at the beginning • Then it follows by pairs of metadata and its size in bytes • Example of file types defined using RIFF: .WAV, .AVI, .CDR, etc RIFF Type •Example of header definition in WAV file: Byte Location 0 4 8 12 16 ... ... Size 4 4 4 4 4 Content ChunkID: ‘RIFF’ ChunkSize FormatID: ‘WAVE’ Subchunk1ID: ‘fmt’ Subchunk1Size: 16 for PCM format MIME Type • Multi-purpose Internet Mail Extensions • It is type declaration of data, earlier meant for email attachment, but now has been used for web transfer as well • It consists of pairs of file extension and its description – some examples: – .au audio/basic – .html text/html – .jpg image/jpeg Text-Based Transfer Text Transfer • Text transfer over the internet nowadays usually involves the standardized process called web service • In its simplest form, web service is any kind of information can be obtained by referring to a URL • Normally web service refers to a text information (not web site layout) obtained from a URL • Two web service standards: SOAP, REST SOAP • Simple Object Access Protocol • Also called RPC – Remote Procedure Call • It is an XML formatted data used to transfer information in web service on HTTP protocol • The standard definition is huge and extensive involving: – Process model – Extensibility Model – Protocol Binding – Message Construct SOAP • It consists of an envelope (surrounding XML) and the data content • Even though it is extensive and hard to learn, use of SOAP is easy and transparent due to large support by programming platforms like .NET, Zend (PHP), J2EE (Java), etc SOAP •Example: POST /InStock HTTP/1.1 Host: www.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"> <soap:Header> </soap:Header> <soap:Body> <m:GetStockPrice xmlns:m="http://www.example.org/stock"> <m:StockName>IBM</m:StockName> </m:GetStockPrice> </soap:Body> </soap:Envelope> REST • REpresentational State Transfer • SOAP’s simpler but competing standard for web service and RPC provider • A web service conforming to REST standard is called RESTful • Its calls resemble normal web address linking • More popular in open source community • Examples of RESTful providers: Amazon.com, Yahoo!, YouTube, eBay, Facebook, etc REST •Examples of RESTful calls: (from URI of http://www.thomas-bayer.com/sqlrest/) <resource> <CUSTOMERList xlink:href="http://www.thomasbayer.com/sqlrest/CUSTOMER/">CUSTOMER</CUSTOMERList> <INVOICEList xlink:href="http://www.thomasbayer.com/sqlrest/INVOICE/">INVOICE</INVOICEList> <ITEMList xlink:href="http://www.thomasbayer.com/sqlrest/ITEM/">ITEM</ITEMList> <PRODUCTList xlink:href="http://www.thomasbayer.com/sqlrest/PRODUCT/">PRODUCT</PRODUCTList> </resource> Text-Based Multimedia in Practice (RSS Feed) RSS Feed • RSS: Really Simple Syndication or Rich Site Summary • It is called syndication because one web site helps to promote the content of other web sites RSS Feed Slides contributed by: MUHAMMAD DZULFAHMI BIN MOHD DZULKIFRI, MUHAMMAD FAUZAN BIN A RAHIM RSS Feed • Has been around for more than a decade • Only recently the standard has been embraced by bloggers, webmasters and large news portals as a means of distributing information, in a standardized format • Defined standard for syndicating headlines and other content • Constructed using XML or extensible Markup Language, which is a markup language similar to HTML RSS Feed Common uses: – Blogs – summaries of daily blog posts – Newsletters – synopses of newsletters alerting users that a new newsletter is available – Weather Alerts – notification of severe weather – Press Announcements – new product announcements – Specials or Discounts – weekly deals or discount offers for customers – Calendars – listings of upcoming events, deadlines or holidays RSS Feed Common industry uses: – Service Industry – notification of viruses or security alerts – Real Estate – listings of open houses or new homes on the market – Schools – homework listings – Restaurants – lunch or dinner specials – Law Enforcement – announce sexual predators in area RSS Feed Subscription: – RSS Feed can be obtained from the website that provides them – The provider will have the specific instruction to get the script to be inserted into the web pages by the web master of the website that subscribes from them – Example of RSS Feed script provided by Google (GModules): • <script src="http://gmodules.com/ig/ifr?url=http://feeds.labnol.org/lab nol&synd=open&w=320&h=200&title=&a mp;border=%23ffffff%7C3px%2C1px+solid+%23999999&am p;output=js"> </script> RSS Feed Screen shot: RSS Feed sponsored link Web 2.0 Web 2.0 • Presumed the next generation of web content • Web 2.0 are webs having the following features: – Visitors can actively contribute to content – Extensive use of web services and API – Extensive use of templates – Extensive use of authoring tools online – Dynamic content by web programs Web 2.0 • Examples of Web 2.0 are: – Facebook – YouTube – Twitter – Blogs – Wikis • One particularly impressive work done by Google to integrate almost all Web 2.0 features into one application is Google Wave Google Wave • Google Wave is an online software application product from Google • Google Wave is designed as a new Internet communications platform • hosted XML documents that allow seamless and low latency concurrent modifications • It was first announced at the Google I/O conference on May 27, 2009. • On May 19, 2010, Google Wave was released to the general public. Google Wave Slides contributed by: MOHD RAHIMI BIN ABDULLAH, MUHAMMED NAFEESH BIN ABDUL RAHMAN Google Wave • Snapshot Google Wave • Google Wave API – Extensions: Build robot extensions to automate common tasks or build gadget extensions to provide a new way for users to interact – Embed: Make your site more collaborative by dropping in a wave Google Wave • Extensions: – Gadgets: A gadget is an application users can participate with, many of which are built on Google’s OpenSocial platform. A good comparison would be iGoogle gadgets or Facebook applications – Robots: Robots are automated participants within a wave. They can talk with users and interact with waves. They can provide information from outside sources (i.e. Twitter, stock quotes, etc.). – The latest version of robots API is 2.0 Google Wave • Protocol – Google Wave provides federation using an extension of XMPP, the open Wave Federation Protocol – Being an open protocol, anyone can use it to build a custom Wave system and become a wave provider