Design and Selection Issues

:Design and Selection Issues 

Analysis An analysis has to be conducted in order to establish the requirements of a system, and to learn the various options available 

 Design Selection Next comes the design phase, which eventually leads to having a specific system to match the requirements. 

 Implementation Next comes the implementation stage, which leads into the operating stage during which the system fulfils its objectives and is modified from time to time to match the minor changes in requirements 

 End & Replacement Eventually the system becomes less effective, for a number of reasons including mechanical faults, arrival of new technologies and major changes in the requirements and in the environment. This stage leads to decay, which finally leads to replacement of the system – starting at step 1 again   

Web Search Engine

: Web Search Engine 

 Search engines are special tools (computer programs) on the web which are designed to help people search for and retrieve information stored on websites 

 Web search engines often help people find information on the web, but they do not guarantee access to the resources they retrieve 

 Search engines normally are free to use by anyone as search tools

Digital Libraries

: Digital Libraries

  A digital library is a digital service normally available on the web that provides search, access, and delivery of organized digital collections of text, image, audio or video files 

 Digital libraries are different from typical online retrieval systems in that they are often free and can be accessed by virtually anyone through the web

Online Retrieval Systems

Online Retrieval Systems 

 Online retrieval systems appeared in the early years of computer application in information retrieval (60s & 70s) 

 Examples of these systems were Dialog, Ovid and RBS. 

 Online retrieval systems are designed to work on many large live databases containing millions of records and some times their documents

  Compared to other systems, online retrieval systems provide very advanced search and retrieval features

  Online retrieval systems are usually fee- or subscription-based services; and they provide access to  peer viewed, quality (often scholarly) information sources

Online Public Access Catalogs (OPACs)

 Online Public Access Catalogs (OPACs) 

 OPACs are typical example of limited features of information retrieval systems 

 An OPAC is mainly used to search for and retrieve information from and about published documents (books, journals, Theses, CDs, DVDs, etc)

  Mainly used by libraries but can be useful for any organization with a collection of published information sources 

 Provide very limited bibliographic entry searches such as title, author (creator), publisher, etc

  OPACs usually have less sophisticated search and retrieval that other categories of information
retrieval system

Kinds of popular information retrieval systems

 Kinds of popular information retrieval systems ➢ Major information  retrieval  systeme 

.  OPACs 

. Online Retrieval Systems 

. Digital libraries.

 . Web search engines

Functions of information an retrieval system:

 Functions of information an retrieval system:

  Identify information (sources) relevant to the interests of targeted user community 

 Analyze the content of information sources (documents) 

 Represent the contents of analyzed sources in a way that matches users’ queries. Currently, this is done by automatically creating one or more index files 

 Analyze users’ queries and represent them in a form that will be suitable for matching databases. Currently, this is made in a number of ways, through the design of sophisticated search interfaces including those that can provide some help to users for selection of appropriate search terms, by using dictionary and thesauri, automatic spell checkers, a predefined set of search statements, and so forth 

 Match search statement(s) with information (documents) in databases. Information retrieval models (will be discussed later) are usually adopted by IRS developers to enable their IRS do the matching between search statements (user queries) and document terms (metadata, descriptors, subject headings, etc.,) 

 Retrieve information (documents). At the end, IRS should retrieve relevant documents that satisfy user needs. Different tools & techniques are used by IRS to determine relevancy