Answers.Body: <p>A recent research example is the &quot;Grind&quot; system. Take a look at the paper <a href="https://arxiv.org/pdf/1804.06907.pdf" rel="nofollow noreferrer">Computing FO-Rewritings in <span class="math-container">$\mathcal{E} \mathcal{L}$</span> in Practice: from Atomic to Conjunctive Queries</a> (2018) by Peter Hansen and Carsten Lutz. Here's the abstract.</p>
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  <p>A prominent approach to implementing ontology-mediated queries (OMQs) is to rewrite into a first-order query, which is then executed using a conventional SQL database system. We consider the case where the ontology is formulated in the description logic <span class="math-container">$\mathcal{E} \mathcal{L}$</span> and the actual query is a conjunctive query and show that rewritings of such OMQs can be efficiently computed in practice, in a sound and complete way. Our approach combines a reduction with a decomposed backwards chaining algorithm for OMQs that are based on the simpler atomic queries, also illuminating the relationship between first-order rewritings of OMQs based on conjunctive and on atomic queries. Experiments with real-world ontologies show promising results.</p>
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Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-06-18T15:44:25.267Z
Answers.LastActivityDate: 2021-01-27T21:25:00.407Z
Answers.LastEditDate: 2021-01-27T21:25:00.407Z
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Body: <p>In the book <a href="https://www.goodreads.com/book/show/2054765.PROLOG" rel="nofollow noreferrer">Prolog Programming for Artificial Intelligence</a>, a large and intricate chapter (chapter 14) is dedicated to Expert Systems. In these systems, a  knowledge-database is represented through facts and rules in a declarative manner, and then we use the PROLOG inference engine to derive statements and decisions.</p>
  <p>I was wondering: are there any examples of <a href="https://en.wikipedia.org/wiki/Expert_system" rel="nofollow noreferrer">expert systems</a> that represent knowledge through a standard Relational Database approach and then extract facts through SQL queries? Is there any research in this area? If not, why is a rule-based approach preferred?</p>
  
Tags: <reference-request><knowledge-representation><expert-systems><rule-based-systems>
Title: Are Relational DBs and SQL used in Expert Systems?
UserDisplayName: olinarr
ThreadText: # Are Relational DBs and SQL used in Expert Systems?
  
  (Asked by: username_0 on 2019-06-17)
  
  In the book [Prolog Programming for Artificial Intelligence](https://www.goodreads.com/book/show/2054765.PROLOG), a large and intricate chapter (chapter 14) is dedicated to Expert Systems. In these systems, a knowledge-database is represented through facts and rules in a declarative manner, and then we use the PROLOG inference engine to derive statements and decisions.
  
  I was wondering: are there any examples of [expert systems](https://en.wikipedia.org/wiki/Expert_system) that represent knowledge through a standard Relational Database approach and then extract facts through SQL queries? Is there any research in this area? If not, why is a rule-based approach preferred?
  
  **Tags:** reference-request, knowledge-representation, expert-systems, rule-based-systems
  
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  ## 1 answers
  
  ### Answer by username_1 on 2019-06-18. Score: 1
  
  A recent research example is the "Grind" system. Take a look at the paper [Computing FO-Rewritings in $\mathcal{E} \mathcal{L}$ in Practice: from Atomic to Conjunctive Queries](https://arxiv.org/pdf/1804.06907.pdf) (2018) by Peter Hansen and Carsten Lutz. Here's the abstract.
  
  > A prominent approach to implementing ontology-mediated queries (OMQs) is to rewrite into a first-order query, which is then executed using a conventional SQL database system. We consider the case where the ontology is formulated in the description logic $\mathcal{E} \mathcal{L}$ and the actual query is a conjunctive query and show that rewritings of such OMQs can be efficiently computed in practice, in a sound and complete way. Our approach combines a reduction with a decomposed backwards chaining algorithm for OMQs that are based on the simpler atomic queries, also illuminating the relationship between first-order rewritings of OMQs based on conjunctive and on atomic queries. Experiments with real-world ontologies show promising results.
  
  
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