Information Retrieval System Explained: Types, Comparison & Components

An information retrieval (IR) system is a set of algorithms that facilitate the relevance of displayed documents to searched queries. In simple words, it works to sort and rank documents based on the queries of a user. There is uniformity with respect to the query and text in the document to enable document accessibility.

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This also allows a matching function to be used effectively to rank a document formally using their Retrieval Status Value (RSV). The document contents are represented by a collection of descriptors, known as terms, that belong to a vocabulary V. An IR system also extracts feedback on the usability of the displayed results by tracking the user’s behaviour.

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When we speak of search engines, we mean the likes of Google, Yahoo, and Bing among the general search engines. Other search engines include DBLP and Google Scholar. 

In this article, we will look at the different types of IR models, the components involved, and the techniques used in Information Retrieval to understand the mechanism behind search engines displaying results. 

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Types of Information Retrieval Model

There are several information retrieval techniques and types that can help you with the process. An information retrieval comprises of the following four key elements:

  1. D − Document Representation.
  2. Q − Query Representation.
  3. F − A framework to match and establish a relationship between D and Q.
  4. R (q, di) − A ranking function that determines the similarity between the query and the document to display relevant information.

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There are three types of Information Retrieval (IR) models:

1. Classical IR Model — It is designed upon basic mathematical concepts and is the most widely-used of IR models. Classic Information Retrieval models can be implemented with ease. Its examples include Vector-space, Boolean and Probabilistic IR models. In this system, the retrieval of information depends on documents containing the defined set of queries. There is no ranking or grading of any kind. The different classical IR models take Document Representation, Query representation, and Retrieval/Matching function into account in their modelling. This is one of the most used Information retrieval models.

2. Non-Classical IR Model — They differ from classic models in that they are built upon propositional logic. Examples of non-classical IR models include Information Logic, Situation Theory, and Interaction models.

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3. Alternative IR Model — These take principles of classical IR model and enhance upon to create more functional models like the Cluster model, Alternative Set-Theoretic Models Fuzzy Set model, Latent Semantic Indexing (LSI) model, Alternative Algebraic Models Generalized Vector Space Model, etc.

Let’s understand the most-adopted similarity-based classical IR models in further detail: 

1. Boolean Model — This model required information to be translated into a Boolean expression and Boolean queries. The latter is used to determine the information needed to be able to provide the right match when the Boolean expression is found to be true. It uses Boolean operations AND, OR, NOT to create a combination of multiple terms based on what the user asks. This is one of the information retrieval models that is widely used. 

2. Vector Space Model — This model takes documents and queries denoted as vectors and retrieves documents depending on how similar they are. This can result in two types of vectors which are then used to rank search results either 

  • Binary in Boolean VSM.
  • Weighted in Non-binary VSM.

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3. Probability Distribution Model — In this model, the documents are considered as distributions of terms and queries are matched based on the similarity of these representations. This is made possible using entropy or by computing the probable utility of the document. They are if two types:

  • Similarity-based Probability Distribution Model
  • Expected-utility-based Probability Distribution Model

4. Probabilistic Models — The probabilistic model is rather simple and takes the probability ranking to display results. To put it simply, documents are ranked based on the probability of their relevance to a searched query. This is one of the most basic information retrieval techniques used

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Components of Information Retrieval Model

Here are the prerequisites for an IR model: 

  1. An automated or manually-operated indexing system used to index and search techniques and procedures.
  2. A collection of documents in any one of the following formats: text, image or multimedia.
  3. A set of queries that serve as the input to a system, via a human or machine.
  4. An evaluation metric to measure or evaluate a system’s effectiveness (for instance, precision and recall). For instance, to ensure how useful the information displayed to the user is. 

The  various components of an Information Retrieval Model include: 

Step 1

The IR system sources documents and multimedia information from a variety of web resources. This data is compiled by web crawlers and is sent to database storage systems.

Step 2

The free-text terms are indexed, and the vocabulary is sorted, both using automated or manual procedures. For instance, a document abstract will contain a summary, meta description, bibliography, and details of the authors or co-authors.

Step 3

File Organization
File organization is carried out in one of two methods, sequential or inverted. Sequential file organization involves data contained in the document. The Inverted file comprises a list of records, in a term by term manner.

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Step 4

An IR system is initiated on entering a query. User queries can either be formal or informal statements highlighting what information is required. In IR systems, a query is not indicative of a single object in the database system. It could refer to several objects whichever match the query. However, their degrees of relevance may vary. 

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Importance of Information Retrieval System

What is information retrieval? Information is a vital resource for corporate operations, and it has to be managed effectively, just like any other vital resource. However, rapidly advancing technology is altering how even very tiny organizations manage crucial business data via information retrieval in AI. A business is held together by an information or records management system, which is most frequently electronic and created to acquire, analyze, retain, and retrieve information.

After we understand what is information retrieval, we need to understand its importance. 

Here are some reasons why Information Retrieval in AI is important in today’s world – 

  • Productive and Efficient – It is unproductive and possibly expensive for small businesses and local companies to have an owner or employee spend time looking through piles of loose papers or attempting to find records that are missing or have been improperly filed. In addition to lowering the likelihood of information being misfiled, robust information storage and retrieval system that includes a strong indexing system also accelerates the storing and information extraction. This time-saving advantage results in increased office productivity and efficiency while lowering anxiety and stress.
  • Regulatory Compliance – A privately owned corporation is exempt from the majority of federal and state compliance regulations, unlike a public company. Despite this, many people decide to voluntarily comply in order to increase accountability and the company’s reputation in public. Additionally, small-business owners are required to retain and maintain tax information so that it is easily available in the event of an audit. A well-organized system for information retrieval in Artificial Intelligence that adheres to compliance rules and tax record-keeping requirements greatly boosts a business owner’s confidence that the operation is entirely legal.
  • Manual vs. Electronic – The value of electronic information retrieval in Artificial Intelligence is based on the fact that they demand less storage space and cost less in terms of both equipment and manpower. An ordered file system may be maintained using a manual approach, but it requires financial allotments for storage space, filing equipment, and administrative costs. Additionally, an electronic system may make it much simpler to implement and maintain internal controls intended to prevent fraud, as well as make sure the company is adhering to privacy regulations.
  • Better Working Environment – Anyone passing through an office space may find it depressing to see important records and other material piled on top of file cabinets or in boxes close to desks. Not only does this lead to a tense and unsatisfactory work atmosphere, but if consumers witness this, it could give them a bad impression of the company. To understand how crucial it is for even a small firm to have efficient information storage and retrieval system.

Difference Between Information Retrieval and Data Retrieval

Data Retrieval systems directly retrieve data from database management systems like ODBMS by identifying keywords in the queries provided by users and matching them with the documents in the database. 

Whereas the Information Retrieval system in DBMS is a set of algorithms or programs that involve storing, retrieving, evaluation of document and query representations, esp text-based, to display results based on similarity.

S.No Information Retrieval Data Retrieval
1 Retrieves information based on the similarity between the query and the document. Retrieves data based on the keywords in the query entered by the user.
2 Small errors are tolerated and will likely go unnoticed. There is no room for errors since it results in complete system failure.
3 It is ambiguous and doesn’t have a defined structure. It has a defined structure with respect to semantics.
4 Does not provide a solution to the user of the database system. Provides solutions to the user of the database system.
5 Information Retrieval system produces approximate results Data Retrieval system produces exact results.
6 Displayed results are sorted by relevance  Displayed results are not sorted by relevance.
7 The IR model is probabilistic by nature. The Data Retrieval model is deterministic by nature.


This brings us to the end of the article. We hope you found the information helpful. If you are looking for more knowledge on Data Science concepts, you should check out India’s 1st NASSCOM certified Executive PG Program in Data Science from IITB on upGrad. 

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What are the applications of the Information Retrieval System?

The Information Retrieval System sets the relationship between data objects and retrieval queries. These documents are prioritized to the user search queries and the best matches are given the highest priority.
The Information Retrieval System is the driving mechanism in of many real-life applications such as:
1. Digital libraries use this system to sort and find the books according to the requested name, genre, or author name.
2. Search engines like Google search use this mechanism to provide accurate and faster search results by matching and prioritizing the documents.
3. Other search platforms such as mobile search, desktop file search, and browser search also run on this technique.
4. Applications such as music streaming apps, video streaming apps, and image libraries use the Information Retrieval operations to search rank the results.

What is the difference between information retrieval and data retrieval?

The following illustrates the differences between information retrieval and data retrieval:
Information Retrieval - Information retrieval deals with the operations like information retrieval, storage, and evaluation of the data. Small errors are neglected. It is an example of a probabilistic model. The final results are not exact and are an approximation. The database user does not get the results.
Data Retrieval - Retrieving the data from the database is called data retrieval. The data retrieval includes identifying and collecting the data from the database. Even a single error can fail the system. It is an example of a deterministic model. The final results are the exact results. The database user gets all the results. The data retrieval system is well structured.

Define user interaction with the IR system?

In the Information retrieval system or IR system, the user first translates the information into a query. The IR system contains a certain set of words that defines the logic to deal with the information.
Earlier, the documents were represented through some keywords or a set of indexes. But it has been modernized and the documents are shown with the whole set of keywords. This can be done with the text operations where the article or connectives are removed/eliminated. This method reduces the complexity of the document as well.

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