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Query languages for the web A way forward By Eva Foster 1 22/05/2017 Query Languages for the web Why is a query language important? What can a query language do for the web? How can it be achieved ? 2 22/05/2017 Why? The need to retrieve information. We are producing more documents for the web than ever. The web is growing. To get information from the web will become even more difficult. 3 22/05/2017 What? 4 Better user interaction with the web. Answer to more specific questions. Improve information retrieval by reducing hits. 22/05/2017 How? Tim Berners-Lee and the W3C proposal include: 5 To structured the web by using the knowledge of the relational database approach. creating standards of how data should be represented. Query the web using SQL technology. Give meaning to the web (The semantic web). 22/05/2017 RDBMS & SQL SQL Request Database Management System Data 6 22/05/2017 Database The benefits of SQL 7 It was created to work with the relational database approach. It is an international standard mechanism for data manipulation. The web contains an enormous amount of relational databases. 22/05/2017 SQL example The Select Statement. SELECT – FROM – WHERE Select * (select all employees) From Employees ( table employees) Where salary “50.000” (salary = 50.000) 8 22/05/2017 Drawbacks 9 to retrieve data from a relational database the data be rigidly structured: schemas, constrains, rules, and standards. SQL works by recognising the structure of the database. Every component of the database must be know for SQL to work. The web is semi structured. 22/05/2017 The semantic web 10 The semantic web follows the principles of relational database. Most data on the web comes from this kind of databases. 22/05/2017 W3C suggestions To achieve a semantic web we need : 11 a flexible markup language (XML) A framework (RDF) An efficient query language 22/05/2017 XML The reasons that XML is convenient: 12 It define a way to structure describe and interchange data. It is self describing. XML can be used for any kind of data. 22/05/2017 A simple XML document <product> <name>Apple</name> <price>0.10</price> </product> THE XML ELEMENT NAME (TAG NAMES) SERVE TO DESCRIBE INFORMATION PROVIDED IN THE DOCUMENT. 13 22/05/2017 DTD Document Type Definition 14 DTD specification is a part of the original XML 1.0 it is a schema that sets out the structure and constraints It allows a developer to specify what elements and attributes may be used in a particular type of XML document. 22/05/2017 RDF- Resource Description Framework 15 RDF integrates a variety of applications using XML for syntax and URIs for naming. It is a model of entities and relationships like the ER entity relationship modelling system. 22/05/2017 RDF GRAPH http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://www.w3.org/People/EM/contac#Person http://www.w3.org/2000/10/swap/pim/contac#fullName http://www.w3.org/People/EM/contac#me Eric Miller mailto:[email protected] http://www.w3.org/2000/10/swap/pim/contac#mailbox Dr. http://www.w3.org/2000/10/swap/pim/contac#personalTitle 22/05/2017 16 RDF/XML <?xml version="1.0"?> <rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#” xmlns:contact=http://www.w3.org/2000/10/swap/pim/contact> <contact:Person rdf:about=http://www.w3.org/People/EM/contact#me> <contact:fullName>Eric Miller</contact:fullName> <contact:mailbox rdf:resource=mailto:[email protected]> <contact:personalTitle>Dr.</contact:personalTitle> </contact:Person> </rdf:RDF> 17 22/05/2017 Structure Query Language for the Web Squeal provides users with the illusion that the Web is stored and organized in a relational database. consists of two parts: 18 a schema describing the Web and an implementation that answers queries about the schema. 22/05/2017 Squeal Squeal explore the semi structure of the web: the text structure. lists, and formatting (hyperlinks) uniform resource locator (URL) host name followed keywords and values. 19 22/05/2017 Example What pages contain "hypertext" and have fewer than 1000 bytes? SELECT url FROM page WHERE contents LIKE '%hypertext%' AND bytes < 1000; 20 22/05/2017 A query language for XML XQuery designed to query non-XML query syntax. XQuery derives from an XML query language called Quilt. Other query languages includes : – – – – – 21 XML-QL, XQL, XPath 1.0 OQL. SQL. 22/05/2017 XML Query XML Request XML Document 22 The Semantic Data Model 22/05/2017 The Web Conclusion 23 The w3C is working to develop new technology to make querying the web easier. The semantic web idea is a important ways in which database and Information Retrieval technologies could interact. A query language for the web can improve information retrieval. 22/05/2017