Indexing and search enginesPresentation Transcript
Indexing and Search Engines Cse(n2) By Jasleen Kaur R. no-115340 Cse(n2)
OVERVIEW Introduction Types of Searching Parts of a Local Search Engine Working of a Local Search Engine Choosing a search engine Conclusion References
Introduction – Searching and Search Engines A good site is one in which ‘content is king’ A lot of information makes a site huge, complex and navigation difficult Search is the users lifeline for mastering complex websites Search feature is essential for users when they revisit a site, looking for specific info
Introduction – Searching and Search Engines Search is also users escape hatch when they are stuck in navigation. When they cant find a reasonable place to go next, they often turn to the sites search function. This is why site search is an important feature of any site of reasonably size
Types Of Searching• A search can be of various types: Internet Search: Search Engines like Yahoo, Infoseek crawl the web gathering web pages or info on web pages, index them and retrieve them when the specific term is found Database search: Databases store their information neatly organized into fields. A search Interface is provided for this.
Types Of Searching With databases one can set up complex queries to find the search words in all applicable fields. But this makes them slower to respond, requires more memory, and requires programming. Database search is not oriented towards text search and relevance ranking: they are great for listing of inventory or directory of the institute
Types Of searching Intranet search: Search is restricted to a site or a group of sites. Text search engines store this information in one index and can find words in any field for a record. Many high-end search engines can also store field information, so searches can be limited to a specific field as well.
Parts of a Local Site Search Tool Search Indexer − The program that recognizes and creates an index of all the documents on the site. The index is stored in a file called as the index file, where the search engine will find them. Search Index File − Created by the Search Indexer program, this file stores the data from the site in a special index or database, designed for very quick access.
Parts of a Local Site Search Tool Search Form − HTML interface to the site search tool, provided for visitors to enter their search terms and specify their preferences for the search Search Engine − The program (CGI, server module or separate server) that accepts the request from the form or URL, searches the index, and returns the results page to the server
Parts of a Local Site Search Tool Results Listing − HTML page listing the pages which contain text matching the search term(s). These are sorted in some kind of relevance order, with the closest match at the top. The format of this is often defined by the site search tool, but may be modified in some ways.
Working of a Local Search Engine Stores Index Search Engine Words Looks in Index Sends Query Gets Matches Indexer Sends Formatted Gets Results words User Selects Search Form required page Results Page User views Retrieved Page Web Site Documents Retrieved Page
Types of Search Engines CGI Programs − The Common Gateway Interface (CGI) standard allows a web server to communicate with external programs. CGI Programs run as Search Engines. Server Plug-Ins − For better data interchange, less overhead and more flexibility, web server companies have defined APIs (Application Programmer Interfaces) to their servers. This allows third-party developers to create modules for the servers which run inside the server process
Types of Search Engines Search Servers Some search engines run as separate servers. The form data is passed as part of − the URL, just like a URL, but the search engine application runs as a separate HTTP server on a different machine. This reduces the load on the main web server. Remote Searching It is also possible to outsource search to a remote site search service. The indexer − and search engine run on the remote server. using a web indexing robot, or spider, they follow links on the site and read the pages, then store every word in the index file on that server. When it comes time to search, the form on the site Web page send a message to the remote search engine which sends results back to the site.
Choosing a Site Search Tool Technical Considerations Indexing Features Searching Capabilities Results display Costs, licensing and registration requirements Unique features (if any)
Features of search engines: Technical ConsiderationsServer platforms Unix, NT, Win95/98/NTsupportedWeb servers NCSA HTTPD, CERN HTTPD, OMNIsupported HTTPD, XITAMI, APACHE, PWS, IISScalability Indexing support for multiple web servers within an intranetTechnical support: E- Mail , Mailing list , Documentation on Web siteMain programmodulesSource codeavailabilityEase of Installation Often related to the technical expertiseand Maintenance available
Features of search engines: Indexing featuresFile/document formats supported HTML, ASCII, PDF, SQL, Spread sheets, WYSIWYG (MS-Word, WP, etc.)Indexing level support File/directory level, multi-record filesStandard formats recognised MARC, Medline, etcCustomisation of documentformatsStemming If yes, is this an optional or mandatory feature?Stop words support If yes, is this an optional or mandatory feature?
Features of search engines: Indexing featuresMeta tags indexing If meta tag indexing is allowed, what kind of meta tags can be usedSupport for compression Does the indexer support file compression?Field level searching Requires more space and timeIndexing ALT text/comment text Shows if the search engine indexes ALT text associated with images or text in comment tags.Database updation Does the indexer support incremental updations?
Features of search engines Search CapabilitiesBoolean Use of Boolean operators AND, OR and NOT asSearching search term connectorsNatural Allows users to enter the query in natural langaugeLangaugePhrase Users can search for exact phraseTruncation Variations of search terms and plural forms can be/wild card searchedExact match Allows users to search for terms exactly as it is enteredDuplicate Remove duplicate records from the retrieved recordsdetectionProximity With connectors such as With , Near, ADJacent one can specify the position of a search terms w.r.t to orhers
Features of search engines Searching featuresField Searching Query for a specific field value in the databaseThesaurus searching Search for Broader or Narrower or Related terms or Related conceptsQuery by example Enables users to search for similar documentsSoundex searching Search for records with similar spelling as the search termRelevance ranking Ranking the retrieved records in some orderCustomization (CGIprgs)Search set manipulation Saving the search results as sets and allowing users to view search history
Features of search engine Results DisplayFormats supported Can it display in native format or just HTML; Display in different formats, Display number of records retrievedRelevancy ranking If the retrieved records are ranked, how the relevance score is indicatedKeyword-in- KWIC or highlighting of matching searchcontext termsCustomization of Allow users to select different displayresults display formatsSaving options Saving in different formats; number of records that can be saved at a time
Choosing the right searchengine• Checklist of factors to be considered while selecting the search engine: – Size of the website – Technical expertise available (local and/or from the supplier / developer) – System platforms available – Information sources and services to be supported – Document collection: type, volume (now and in future) – Indexing, search and display requirements
Choosing the right searchengine• Checklist of factors to be considered while selecting the search engine: – User community to be served – Differentiate between the need for indexing the web site pages and the need for indexing databases / document collections (text, bibliographic, DBMS, etc.) – Support for the concept of a "record" by the search engine. – Support for structured fields and metadata – Cost
Choosing the right searchengine• Steps in the selection and procurement of search engines: - Conduct a needs analysis. - Talk to other libraries - Attend trade shows and talk to vendors - Read the literature that reviews searchengines. - Compile a list of possible products..
Choosing the right searchengine• Steps in the selection and procurement of search engines: – Compare the functionality of each product to the criteria you developed through needs analysis – Narrow your list down to three possible products. – Spend additional time learning about each product. – Invite the vendors in for demonstrations. – Ask for references and follow up with each reference – Select product and implement. – Follow up with end users. – Continue an on going review with end users.
Choosing the right searchengine• Some Suggestions – The search system development or selection should be based primarily on the local needs – Consider using freeware search engines, if your requirements are met by these. – For large, highly developed intranet sites, you may like to consider commercial search engines – Consider if the webserver you are using supports indexing and search, and if this is adequate for you.
Choosing the right searchengine – The IT Professionals should make an effort to keep themselves abreast of the current web technologies – The features available within a tool should be made use of properly to get maximum benefits – Carefully consider interrelations between the three major components: document resources, users and the search engines.
Conclusion Since search is such a common activity, the search box should appear on every page of your web site. The initial target of the basic search should be the contents of the entire web site. The basic search should allow for Boolean commands ("and," "or"), although this does not need to be explained.
Conclusion A quality search process begins with quality metadata. Its that old principle: Garbage in, garbage out. Metadata is about giving a structure the the content. For example, if every document is assigned keywords or or classified by Geography, the reader will get a much more accurate return from his or her search. Search engines are the mortar of the Intranet. As important as they are, their implementation must be given high priority with the necessary time allotted for research and development
List of some Popular Search Engines Google http://www.google.com Yahoo http://www.yahoo.in Bing http://www.bing.in Amazon http://www.amazon.com
Free and commercial searchengines• Commercial search engines – AltaVista (www.altavista.digital.com/) – Fulcrum (www.fulcrum.com/ ) – Infoseek (software.infoseek.com) – Open Text (www.opentext.com/) – Oracle (www.oracle.com/) – PLS (www.pls.com/) – Verity (www.verity.com/)