Institute for Visualization and Perception Research 1 © Copyright 1998 Haim Levkowitz World-Wide Web Introduction to the World-Wide Web Setting up a Web server Authoring for the Web... Gateways and forms Access control and security

Institute for Visualization and Perception Research 2 © Copyright 1998 Haim Levkowitz History... CERN, Geneva, 1989 Def HTTP client/server protocol Sample server Prog. lib. wwwlib 1992: callable interface in public domain ==> Development Web browsers New features Now browsers & servers for all major architectures

Institute for Visualization and Perception Research 3 © Copyright 1998 Haim Levkowitz Original goals Link distinct documents Success Facilitate collaborative authoring Not so much, yet

Institute for Visualization and Perception Research 4 © Copyright 1998 Haim Levkowitz Introduction to the World- Wide Web Components of Web architecture... What's the Web good for?... Basic Web Concepts... WWW Servers and Browsers... Searching on the Web …

Institute for Visualization and Perception Research 5 © Copyright 1998 Haim Levkowitz Components of Web architecture … HTML: Hyper Text Markup Language HTTP: Hyper Text Transfer Protocol CGI: Common Gateway Interface Web clients Web servers Databases Contents Software applications CGI TCP/IP-based network

Institute for Visualization and Perception Research 6 © Copyright 1998 Haim Levkowitz Powerful linking abilities... Highlight words/pictures ==> Link/point to other Documents Sound files Movie clips From any point to any point

Institute for Visualization and Perception Research 7 © Copyright 1998 Haim Levkowitz Most graphical Internet service... Need browser w/GUI Click on link to follow

Institute for Visualization and Perception Research 8 © Copyright 1998 Haim Levkowitz What's the Web good for?... Museums Newspapers, magazines Business Investment information Libraries, universities Governments Individuals

Institute for Visualization and Perception Research 9 © Copyright 1998 Haim Levkowitz Basic Web Concepts... Hyperlinking... The HTML Tagging Language... The URL Concept... What's a WWW Browser?... What's a WWW Server?... HTTP...

Institute for Visualization and Perception Research 10 © Copyright 1998 Haim Levkowitz Hyperlinking... Home page: central doc. in Web server Hyperlinks (underlined) Navigate: follow hyperlinks (surfing) Anywhere on Web servers in the world!...

Institute for Visualization and Perception Research 11 © Copyright 1998 Haim Levkowitz Anywhere on Web servers in the world!...

Institute for Visualization and Perception Research 12 © Copyright 1998 Haim Levkowitz The HTML Tagging Language... Hypertext Markup Language HTML Documents Describe structure of doc & hyperlinking info No exact formatting Example...

Institute for Visualization and Perception Research 13 © Copyright 1998 Haim Levkowitz Example....

Institute for Visualization and Perception Research 14 © Copyright 1998 Haim Levkowitz The URL Concept... Each hyperlink, 2 components: Anchor text/graphics Trigger hyperlink when clicked Universal Resource Locator (URL)...

Institute for Visualization and Perception Research 15 © Copyright 1998 Haim Levkowitz Universal Resource Locator (URL)... What to do when HL activated Protocol to reach Target server Host system (server name) where doc is Directory path Filename E.g., master list of all public WWW server in world Geographical.html (absolute)

Institute for Visualization and Perception Research 16 © Copyright 1998 Haim Levkowitz What's a WWW Browser?... Client/server environment Browser Use URL Retrieve Web document from Web server Interpret HTML Present document to user Bitmap graphics ==> more than char. based E.g., hyperlink: color/underline vs. reverse video Example...

Institute for Visualization and Perception Research 17 © Copyright 1998 Haim Levkowitz Example... Protocol depends on server Some browsers can access WAIS servers Can start up telnet sessions Can save, , print, search, see HTML source

Institute for Visualization and Perception Research 18 © Copyright 1998 Haim Levkowitz What's a WWW Server?... SW used with WWW Client asks for page; server grabs & returns Special scripts Gateways to other info resources E.g., input from forms Custom scripts to process

Institute for Visualization and Perception Research 19 © Copyright 1998 Haim Levkowitz HTTP... HyperText Transfer Protocol Request browser --> server ==> new connection Open connection Transfer document Close connection Data types between server and browser Text (text/html, text/plain,...) Image (image/gif, image/tiff,...) E.g., start xv to display (Preferences: Helper App's)

Institute for Visualization and Perception Research 20 © Copyright 1998 Haim Levkowitz WWW Servers and Browsers... Browsers... Servers...

Institute for Visualization and Perception Research 21 © Copyright 1998 Haim Levkowitz Browsers... Netscape Navigator/Communicator Internet Explorer Mosaic (historic importance) Lynx (dumb terminal) Amaya (free) Browser/editor ( Opera (not free)

Institute for Visualization and Perception Research 22 © Copyright 1998 Haim Levkowitz Mosaic... The first publicly available browser Made it happen!

Institute for Visualization and Perception Research 23 © Copyright 1998 Haim Levkowitz Netscape Navigator... Netscape Communications Corp. (former Mosaic Comm.)

Institute for Visualization and Perception Research 24 © Copyright 1998 Haim Levkowitz Lynx... Full-screen, character-based VT100 terms, emulators Arrow keys to navigate among HTML links (reverse video) Bookmarks Forms Interactive mode: post articles to newsgroups Non-interactive mode: filter HTML to formatted ASCII ftp://ftp2.cc.ukans.edu/pub/lynx/

Institute for Visualization and Perception Research 25 © Copyright 1998 Haim Levkowitz Many others Came and went Maybe 10% of today’s users

Institute for Visualization and Perception Research 26 © Copyright 1998 Haim Levkowitz Servers... NCSA CERN Apache (48% of all servers) Netscape Enterprise O’Reilly’s WebStar Other

Institute for Visualization and Perception Research 27 © Copyright 1998 Haim Levkowitz NCSA... Public domain, written in C, small, fast No licensing restrictions Compatible with most HTTP browsers Directory aliasing: doc's can be served from any physical directory structure Searches, HTML forms, clickable image maps, control user access. Compiled.html

Institute for Visualization and Perception Research 28 © Copyright 1998 Haim Levkowitz CERN... Public domain, written in C No licensing restrictions Compatible with most HTTP browsers Directory aliasing: doc's can be served from any physical directory structure Searches, clickable image maps, control user access Proxy & caching On firewall machines access to outside world from inside

Institute for Visualization and Perception Research 29 © Copyright 1998 Haim Levkowitz Work in progress... See User Interface Technology & Society Architecture Web Accessibility Initiative Other

Institute for Visualization and Perception Research 30 © Copyright 1998 Haim Levkowitz User Interface HTML Enhancements Style Sheets Document Object Model Mathematics Graphics Internationalization Fonts Amaya

Institute for Visualization and Perception Research 31 © Copyright 1998 Haim Levkowitz Technology & Society Digital Signature Initiative Metadata PICS Privacy Security Electronic Commerce

Institute for Visualization and Perception Research 32 © Copyright 1998 Haim Levkowitz Architecture HTTP Synchronized Multimedia XML Jigsaw Libwww

Institute for Visualization and Perception Research 33 © Copyright 1998 Haim Levkowitz Web Accessibility Initiative Accessibility of the Web Through five primary areas of work: Technology Guidelines Tools Education & outreach Research & development

Institute for Visualization and Perception Research 34 © Copyright 1998 Haim Levkowitz Secure Transactions... Credit card numbers Signatures (electronic) Legally binding time stamps Secure HTTP development Authority of transactions Confidentiality of info exchanged ndards/drafts/shttp.txt

Institute for Visualization and Perception Research 35 © Copyright 1998 Haim Levkowitz Uniform Naming... URL: no uniquely identify doc Only instance of doc No account for mirrored doc's, versions out of date URN: Universal Resource Name Unique doc identifier Like ISBN for books Return URL of closest copy? URC: Universal Resource Citation (just a diff name)

Institute for Visualization and Perception Research 36 © Copyright 1998 Haim Levkowitz Commercialization... Bundle browser w/systems License browsers + sell ==> Web onto more desktops Info providers + publishers Secure web ==> electronic commerce

Institute for Visualization and Perception Research 37 © Copyright 1998 Haim Levkowitz Searching on the Web... Catalogs, directories Manual E.g., Yahoo Indices, search engines Automatic E.g., AltaVista

Institute for Visualization and Perception Research 38 © Copyright 1998 Haim Levkowitz Search Engines... "Robots," "worms," "spiders," "crawlers,” meta searchers No ultimate search tool on the Web Different search strategies ==> Different results Partial list... More info...

Institute for Visualization and Perception Research 39 © Copyright 1998 Haim Levkowitz Partial list... Metacrawler... Alta Vista... WebCrawler... Lycos InfoSeek Copernic

Institute for Visualization and Perception Research 40 © Copyright 1998 Haim Levkowitz Comparison... IEEE Internet Computing, July/August 1998, pp , ach.htm /Compare/Search/ (old)

Institute for Visualization and Perception Research 41 © Copyright 1998 Haim Levkowitz More info... "New Spiders Roam the Web" piders.html "WWW Robots, Wanderers, and Spiders" ml Netscape Web page search.html Click Net Search button in Netscape

Institute for Visualization and Perception Research 42 © Copyright 1998 Haim Levkowitz Internet Research Tool Kit Links to most search & research tools rch_links.html