Semantic Web :: Data Engineering Foundations

1. Introduction

Mon, 01 Jan 0001 00:00:00 +0000

Definition The Semantic Web enables machines to understand the semantics and meaning of information on the Web. It extends the network of hyperlinks between traditional web pages with a network of links between structured data, enabling automated agents to access different data sources on the web more intelligently and thus perform tasks (search, learning, etc.) more accurately for users. The term semantic web was coined by Tim Berners-Lee, co-inventor of the web and director of the W3C, which oversees the development of proposals for semantic web standards.

2. Linked data and RDF Model

Mon, 01 Jan 0001 00:00:00 +0000

Definition The Web of Data (linked data) is an initiative of the W3C (World Wide Web Consortium) aimed at promoting the publication of structured data on the Web, not in the form of isolated data silos, but by linking them together to form a global network of information. The aim of the web of data is to put online, in addition to documents, structured data that can be interpreted by computer programmes. Thus, in addition to being a huge media repository, the web is becoming a global database that computer scientists can use to develop applications.

3. Ontologies and OWL Syntax

Mon, 01 Jan 0001 00:00:00 +0000

Definition An ontology is a way of modelling a domain by identifying its concepts, organising them in relation to each other, identifying the properties that connect them, and designating the objects that represent them. 3.1 Introduction 1- OWL (Ontology Web Language) OWL is the language recommended by the W3C for expressing ontologies. It is characterised by the following: It uses URIs to designate all its elements. It adopts a set-theoretic view of ontologies: concepts are sets, objects are elements of sets, and properties connect these elements. The set of all sets is represented by the URI owl:Thing, where owl is the prefix for: http://www.w3.org/2002/07/owl# OWL classes represent sets, instances represent their elements, and properties allow links to be created between instances. 2- The set-theoretic principle of OWL In the semantic web, an ontology defines a domain through classes, individuals, and properties. Each class can be interpreted mathematically as a set of individuals that share certain characteristics. In mathematics, the algebra of sets, defines the properties and laws of sets, the set-theoretic operations of union, intersection, and complementation and the relations of set equality and set inclusion. It also provides systematic procedures for evaluating expressions, and performing calculations, involving these operations and relations.

4. SPARQL query Language

Mon, 01 Jan 0001 00:00:00 +0000

Definition SPARQL is a query language and protocol that allows to search, add, modify or delete RDF data. Its name is a recursive acronym that stands for SPARQL Protocol And RDF Query Language. 4.1 Introduction A SPARQL query is the expression of an RDF graph in which some nodes or properties are not URIs or values, but variables. Finding one or more solutions to a query consists of finding a subgraph in the database graph whose topology, URIs, and values correspond to those of the query. The solution(s) are the URIs or values that the variables must take for the match to be established. SPARQL is based on the Turtle syntax.

5. Raisonning and SWRL Language

Mon, 01 Jan 0001 00:00:00 +0000

Definition A rule expresses reasoning of the form “if antecedent then consequent. It is formulated as follows: antecedent → consequent, where: antecedent, also called a premise or body of the rule, represents a conjunction of conditions (atoms) for applying the rule, consequent, also called head of the rule, is the the result of applying the rule. 5.1 Rules in propositional logic Rule : p1 ∧ p2 ∧ … pn → c ≡ ¬p1 ∨ ¬p2 ∨ …∨ ¬pn ∨ c

Ontologies : Practical Activities

Mon, 01 Jan 0001 00:00:00 +0000

Duration1h15 AI Banned The Protégé environment Protégé is a free and open source ontology editor that provides a framework for designing intelligent systems. It enables the design of knowledge-based systems in various fields such as e-commerce and biomedicine. The following activities will familiarise you with this environment so that you can manipulate and even design ontologies.

Raisonning and SWRL : Practical Activity

Mon, 01 Jan 0001 00:00:00 +0000

1 - The family ontology Duration1h15 AI Banned Launch the Protégé environment and import the Family ontology locally. Family Ontology Add a tab dedicated to inference rules by performing the following actions: Window /create new tab, name it Rules, for example. Then Window/Views/Ontology Views/ Rules You can then view the existing rules associated with the ontology. Run an reasonner and view the result. Throughout this activity, remember to save any changes made to this ontology. The save format must be RDF/XML Syntax. You can check the RDF/XML syntax of your ontology by displaying the RDF/XML Rendering tab.

RDF Graphs : Practical Activities

Mon, 01 Jan 0001 00:00:00 +0000

Duration1h15 AI Banned 1 - Small family Create a simplified RDF graph describing the following statements : Margot is a woman and a journalist, she is 32 years old, she is married to Arthur, who is a man and a photographer. Together, they have two children, Marie, a girl who loves robots, and Simon, a boy who enjoys painting. Each person must be represented as a URI : :Margot, :Arthur, :Marie, :Simon. Each family member should be associated with their names as literal values (Margot, Arthur, Marie, Simon). Specify gender with the URIs : rdf:type, voc:Woman, voc:Man Attributes like name, age, profession and hopbby must be represented with URIs as predicates : voc:name, voc:age, voc:occupation, voc:hobby Family relations must be represented with URIs as predicates : voc:hasChild, voc:hasSpouse, Draw the RDF graph on a paper, before providing it in the Turtle language.

SPARQL : Practical Activity

Mon, 01 Jan 0001 00:00:00 +0000

Duration1h15 AI Banned In this activity, we will formulate SPARQL queries on a small ontology called Family Family Ontology Launch the Protégé environment and then import the Family ontology locally. Explore the ontology to understand its content. Display the SPARQL Query tab in the Protégé interface: Window/Tab/SPARQL Query Add the prefix associated with the Family ontology so that you can query it in the header of your query editor as follows: PREFIX family: Run the default query and save it in a separate file. It will help you formulate other queries. Remember to save your queries in a separate file (e.g., .txt), because each new query will force you to delete the previous one. Then find the queries that display the following results: Display all of Jason’s object properties and their values. Display the list of individuals and their spouses (defined by the hasConsort property). Display the number of women and the number of men. Display parents having two children. Display the profiles of all individuals, grouping them together. This must include the object properties and their values for each individual. Display individuals who have at least one sibling. Display the full family tree of Jason. Display individuals who have no spouse (requires FILTER NOT EXISTS). Use the keyword SELECT DISTINCT to avoid repetition of results when necessary.