INFS 427: AUTOMATED INFORMATION RETRIEVAL (1 st Semester, 2018/2019)

Transcription

1 INFS 427: AUTOMATED INFORMATION RETRIEVAL (1 st Semester, 2018/2019) Session 01 Introduction to Information Retrieval Lecturer: Mrs. Florence O. Entsua-Mensah, DIS Contact Information: College of Education School of Continuing and Distance Education 2014/ /2017

2 Session Overview This lecture session sets the pace for studying automated information retrieval systems. It introduces leaners to the concept of information retrieval, and the systems that are used to automate the information retrieval process. Florence O. Entsua-mensah (Mrs), DIS/SCDE Slide 2

3 Session Outline The key topics to be covered in the session are: Topic One: Understanding Information Retrieval Topic Two: Information Retrieval System Florence O. Entsua-Mensah (Mrs) 3

4 Recommended Reading Chowdhury, G. G. (2010). Introduction to modern information retrieval. London: Facet publishing. Read Chapter One. Florence O. Entsua-mensah (Mrs), DIS/SCDE Slide 4

5 Topic One UNDERSTANDING INFORMATION RETRIEVAL Florence O. Entsua-mensah (Mrs), DIS/SCDE Slide 5

6 Defining Information Retrieval (IR) IR is finding material (usually documents) of an unstructured nature (usually text) that satisfies an information need from within large collections (usually stored on computers). IR includes: Web search Searching your laptop Searching large cooperate databases Florence O. Entsua-Mensah (Mrs) 6

7 Definition of IR Information retrieval The technique & process of searching, recovering, & interpreting information from large amounts of stored data (MScience & Technology Dictionary) It relates to the organization of, processing of, and access to information of all forms and formats (Chowdhury, 2010)

8 Basic assumptions of IR Collection: A set of documents Assume it is a static collection for the moment Goal: Retrieve documents with information that is relevant to the user s information need and helps the user complete a task. Precision : Fraction of retrieved documents that are relevant to the user s information need. Recall : Fraction of relevant docs in collection that are retrieved. (Manning, Raghavan, & Nayak, 2015) Florence O. Entsua-Mensah (Mrs) 8

9 The Classical Search Model (Manning, Raghavan, & Nayak, 2015) Florence O. Entsua-Mensah (Mrs) 9

10 Topic Two (2) INFORMATION RETRIEVAL SYSTEM (IRS) Florence O. Entsua-mensah (Mrs), DIS/SCDE Slide 10

11 The nature of an IR system Structured vrs unstructured data Structured data (e.g., students database): Data elements are related Designed to retrieve specific facts or records, based on a common attribute of the data elements (e.g., student ID or gender.). IR deals with unstructured data: No clearly defined data elements All types of documents; e.g., abstracts or full text documents such as newspapers, dictionaries, encyclopaedias, handbooks, audio, video, images etc.

12 The purpose of an IR system To organize documents/records in a way that facilitates easy access or retrieval of relevant information by its users. IR systems retrieve bibliographic items or exact match of texts of queries from full text databases or multimedia information.

13 Elements of an IRS

14 The IR Process Documents in an IRS are processed into an index (Indexing process) A user formulates his problem/information need in a query (Query formulation) The IR software compares/matches the query to the index (Matching process) The user is presented with a set of retrieved documents which he judges for relevance or appropriateness in meeting his need (Feedback) The query can be modified if the retrieved documents are irrelevant

15 Characteristics of an effective IR system Must be equipped for: Prompt information dissemination Information filtering (exclude unwanted information) Active switching of information (Such as switching from web search to access) Receiving information in a desired format Browsing Getting information in an economical way Current literature Accessing other information systems Interpersonal communication Personalized help, and must be User friendly, i.e., must consider the convenience of the user(liston and Schoene (as cited by Chowdhury, 2010)

16 Types of IR systems 1. OPAC Searching library catalogues online checking availability of library resource. 2. Online database Provide access to peer reviewed scholarly information resources Are subscription or fee-based services 3. Digital libraries and web information service Information is stored in digital formats Often free and accessed via the web 4. Web search engines Free search tools for web information retrieval

17 Everyday uses of IR systems Search for information from library OPACs Access information from bibliographic or full text databases e.g. Web of Science, LISA Access to e-books & e- journals (World public library at Emerald at Access information from services and mobile phones Search information on company or institutional intranets Access web information via URLs, search engines, and subject gateways (provide links to more academic, reliable information). Access information from social networking sites.

18 Summary In this session we have learnt what information retrieval is generally concerned with. The session also discussed the nature and characteristics of information retrieval systems. Florence O. Entsua-Mensah (Mrs) 19

19 References Chowdhury, G. G. (2010). Introduction to modern information retrieval. London: Facet publishing Florence O. Entsua-Mensah (Mrs) 21