Using the WWW

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Using the WWW

• Miroslav Milinovic
• Croatian Academic and Research Network - CARNet
• Zagreb, Croatia

5th CEENet Workshop on Network Technology,
Budapest, Hungary, August 1999.
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Using the WWW (Part 1)Introduction to WWW
information service
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Content

• Computer network ? Information network
• WWW - important concepts (HTML, URL, HTTP)
• How WWW works?
• WWW client - browser
• HTML file Web page
• Netscape browser
• Client - server communication
• Server status codes
• Active Web pages
• Internationalization
• Security

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Computer network
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Information network
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WWW - World Wide Web

• Distributed, multimedia information service based
  on hypertext
• Distributed
• information located on hosts around the world
• Multimedia
• information includes text, graphics, sound, video
• Hypertext
• hypertext techniques used to enable access to the
  information

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WWW - important concepts

• Uses Client/Server Architecture
• client programs known as browsers
• Netscape, MS IE, Amaya, Hot Java, Tango, Lynx,
  ...
• Provides access to Internet resources
• provides access to WWW resources as well as
  FTP, NEWS, Gopher, ...
• brings together whole range of services

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WWW - important concepts

• WWW resources - documents are prepared using
  simple standard markup language which defines
  document
• content, presentation, links to the other
  documents
• Documents have a unique identifier
• depends on their location on a particular host
• Clients can communicate with any server
• using correct protocol

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WWW - important concepts

• HTML - HyperText Markup Language
• language for preparing the WWW documents
• URL - Uniform Resource Locator
• resource address unique identifier
• HTTP - HyperText Transport Protocol
• defines communication between WWW client and
  server

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HTML

• HTML is the native language of the WWW
• HTML file Web page
• standards
• HTML 1.0, 2.0, 3.0., 3.2, 4.0,
• browser extensions (Netscape, MS IE, ...)
• other (VRML, DHTML, SMIL, MathML, CSS, XML, XSL,
  ...)
• XHTML 1.0 (in draft)

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URL - locating Internet resources

• URL is unique identifier for Internet resources
• indicates
• means of access
• location
• simple syntax
• protocol//host_nameport_num/path/file_name
  
• example
• http//www.ceenet.org/constitution.html

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Internet resources identification

• URI - Uniform Resource Identifier
• URL - Uniform Resource Locator
• PURL - Persistent URL
• URN - Uniform Resource Name
• URC - Uniform Resource Characteristics
• data about the networked resource
• metadata data about data

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HTTP

• application-level protocol
• stateless
• supports
• use of URLs
• Internet media types (MIME types
  RFC2045-RFC2049)
• allows access to different data formats
• standards
• HTTP 1.0 (RFC 1945), HTTP 1.1 (RFC 2068, 01.97.)

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How WWW works?
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How WWW works?
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WWW client - browser

• retrieve (display if possible) various resources
• can be
• text-only (Lynx, ...)
• graphic (Netscape, ...)
• there are some differences in displaying HTML
  documents between different clients
• can display a variety of formats
• TEXT, GIF, JPEG, ...

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WWW client - browser

• has multiprotocol support
• HTTP, FTP, GOPHER, NNTP, SMTP, POP, ...
• can automatically launch helper application
  (viewer)to handle some data formats (sound,
  video, postscript, MS applications, ...)
• plug-in extensions can be used to extend
  browser capabilities (3D animation, various
  graphics formats, ...)

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HTML file Web page
HTML source
Web pagedisplayed by browser
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Netscape browser
Title line
Menus
Icons
URL
HTML document
Hyperlink
Status line
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Client - server communication

• Simple client request (entered manually)
• telnet www.srce.hr 80
• Trying 161.53.2.69...
• Connected to regoc.srce.hr.
• Escape character is ''.
• GET /index.html HTTP/1.0
• ACCEPT /
• USER-AGENT manually entered HTTP
• (blank line)

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Client - server communication

• Server reply
• HTTP/1.0 200 OK
• Date Tue, 29 Jul 1997 125615 GMT
• Server Apache/1.1.3
• Content-type text/html
• Content-length 2320
• Last-modified Fri, 22 Nov 1996 100727 GMT
• (blank line)
• (content - document source)

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Server status codes

• Status codes are three digit numbers grouped as
  follows
• 1xx - informational
• 2xx - client request successful
• 200 - OK
• 3xx - request redirected
• 4xx - client errors (request incomplete)
• 403 - Forbidden
• 404 - Not found
• 5xx - server errors

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Active Web pages

• enhanced Web
• two way interaction
• page animation
• browser intelligence
• desktop integration
• better multimedia
• access to other systems
• common examples
• forms (feedback processing)
• active maps (clickable maps)
• (database) gateways

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Active Web pages

• techniques
• CGI - Common Gateway Interface
• WWW server communicates with other programs (CGI
  scripts)
• SSI - Server Side Includes (.shtml)
• API - Application Programming Interface
• Cookies (making a browser remember)
• scripting languages (embedded in HTML document)
• Javascript, VBscript,
• DHTML
• Java (applets, servlets)
• ActiveX

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Active Web pages

• Who is doing the job?
• browser downloads and automatically executes
  program (Java applet)
• OR
• HTML document is generated on the server machine
  (by CGI script)

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Active Web pages
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Internationalization

• originally
• plain ASCII (Latin 1) English language
• HTML internationalization (RFC 2070)
• UNICODE language attribute in HTML
• HTTP 1.1
• enables charset and language negotiation

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Security

• plain WWW is not secure!
• security on
• content level
• PGP, data encription
• channel level
• SSL (Secure Socket Layer)
• message level
• SHTTP, PEP, ...

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Questions ?
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Using the WWW (Part 2)Searching the Internet
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Content

• Internet information space
• Searching with the WWW
• Searching the WWW
• Search Engines
• Metasearch Engines
• Subject Catalogs
• Other tools
• Conclusion on search tools
• Selecting a tool
• A Strategy?

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Internet information space

• is NOT unified
• many subjects
• different formats
• different resources (information services)
• various tools and techniquesfor searching and
  information retrieval
• some information is not (yet)
• published electronically
• available on the Net

Internet
printed
WWW
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Searching with the WWW

• searching tools
• many different tools
• various concepts
• specialized for chosen resources
• WWW, gopher, Netnews, FTP, databases, ...
• global or local scope
• main problems quality and currency
• there is NO perfect tool
• user needs a strategy

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Searching the WWW

• Search Engines
• Search Engines
• Metasearch Engines (Unified Search Interfaces)
• Subject Catalogs (Virtual Libraries)
• Other tools
• Multiple Search Interfaces
• Information Gateways
• Portals

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Search Engines

• automated systems
• specially designed programs
• robots, crawlers, spiders
• fetch WWW documents
• index those documents to build database
• provide interface for user to search the database
• query syntax
• searching features
• presentation of the results - hits (format,
  ranking)

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Search Engines
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Search Engines

• examples
• Alta Vista - http//altavista.digital.com/
• excite! NetSearch - http//www.excite.com/
• InfoSeek - http//www.infoseek.com/
• HotBot - http//www.hotbot.com/
• Lycos Search - http//www.lycos.com/
• WebCrawler - http//www.webcrawler.com/
• Nothern Light Search - http//www.northernlight.co
  m/
• Google - http//www.google.com/
• Ask Jeeves! - http//www.ask.com/
• local (regional) search engines

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Search Engines

• query syntax and searching features
• upper and lower case letters
• John December
• island
• phrases (text in quotes - ...)
• NASA space shuttle program
• John December
• Boolean operators (AND, OR, NOT) and parentheses
  (...)
• vegetable AND green
• fruit NOT apple
• keyword control (, -)
• film noir -pinot noir
• pyton -monty

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Search Engines

• query syntax and searching features
• proximity search (NEAR)
• Internet NEAR training (Alta Vista)
• keyword truncation ()
• alumium
• comput
• cascade search (Infoseek)
• resource control (AltaVista, HotBot, Infoseek)
• titleInternet training
• natural language searching (Ask Jeeves!)
• ...

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Search Engines

• important characteristics
• database (quantity quality)
• query language
• response time
• ranking (hits)
• output (format, available info)
• additional features (cascade search, refine, )
• ...

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Search Engines

• advantages
• vast number of documents (over 100 million)
• highly efficient searching and retrieval
• automated production
• disadvantages
• no quality control
• no classification
• hits can be out of context
• dead or out-of-date links, junk

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Metasearch Engines

• Unified Search Interfaces
• automated systems
• DO NOT build databases of their own
• query other search engines
• provide unified interface for user to search a
  number of databases (search engines) with one
  query

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Metasearch Engines

• examples
• All4one - http//all4one.com/
• Mamma - http//www.mamma.com/
• MetaCrawler - http//www.metacrawler.com/
• SavvySearch - http//www.savvysearch.com/

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Metasearch Engines

• important characteristics
• number and selection of search engines covered
• query language
• response time
• ranking (hits)
• results (hits) merging
• output (format, available info)
• additional features
• ...

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Metasearch Engines

• advantages
• same as search engines
• make use of search engines easier
• disadvantages
• same as search engines
• unified query for all search engines means loss
  of additional capabilities of particular search
  engine
• searching is slower

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Subject Catalogs

• Virtual Libraries, Subject Directories
• collections of Internet resources descriptions
• names, URLs, abstracts, ratings, ...
• organized within hierarchical subject scheme
• heuristic (subject based)
• UDC, Dewey, ...
• manually maintained
• internal search

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Subject Catalogs

• examples
• Yahoo - http//www.yahoo.com/
• EINet Galaxy - http//galaxy.einet.net/
• Magellan - http//magellan.excite.com/
• NetGuide - http//www.netguide.com/
• BUBL - http//bubl.ac.uk//link/
• WWlib - http//www.scit.wlv.ac.uk/wwlib/
• WWW.HR - http//www.hr/wwwhr/

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Subject Catalogs

• important characteristics
• size
• classification method
• available info (about classified resources)
• ranking
• (internal) searching
• additional features
• ...

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Subject Catalogs

• advantages
• classified into subject areas
• manually reviewed resources (no junk)
• internal search
• disadvantages
• manual maintenance
• out-of-date information
• catalogue (some parts) is not professional

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Other tools

• Multiple Search Interfaces
• simple Web pages with interfaces to number of
  search tools
• enable user to choose among listed tools
• DO NOT build databases of their own
• DO NOT act as Metasearch Engines
• examples
• All-in-One - http//www.allonesearch.com/
• Easy Searcher - http//www.easysearcher.com/

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Other tools

• Information Gateways
• dedicated to one subject (e.g. Social Sciences)
• examples
• SOSIG - http//sosig.ac.uk/
• OMNI - http//www.omni.ac.uk/
• And ...
• electronic dictionaries, encyclopedias, guides,
  software collections, map collections,
  databases, tools for searching non-www
  resources,

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Conclusion on search tools

• each tool has advantages and disadvantages
• new systems appear, old stagnate
• CAUTION tools are text oriented
• non-WWW resources are also covered
• quality and currency
• precision .vs. recall
• cooperation between tools is a necessity
• winner portal
• hybrid tool (Search Engine with Catalog)
• brings together many (all) network services

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Selecting a tool

• Search Engines
• when you have good (precise) keywords (narrow
  topic)
• Subject Catalogs
• for look and feel
• when you dont have good keywords (broad topic)
• Information Gateways or other specialized tools
• for quality (if you can find one)
• Multiple Search Interfaces
• useful to see what is available
• Portals
• tools for the future

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A Strategy?

• no searching system is prefect
• be flexible and try different tools
• compare results and gain experience
• learn vocabulary, read HELP and FAQ
• be focused (dont wander around)
• concentrate on problem, not on tool (query)
• use stepwise approach
• refine query (keywords)

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Questions ?