Semantic Web Technologies Lecture # 2 Faculty of Computer Science, IBA

Lecture Outline Semantic Web at present Semantic Web goals. Semantic Web technologies – Explicit Metadata – Ontologies – Logics – Agents Quratulain2

Semantic Web To date Web has developed most rapidly as a medium of documents for people rather than data and information that can be processed automatically. The Semantic Web aims to provide data that is machine processable. The Semantic web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation. Quratulain3

Semantic Web: At present Researchers claim that the challenge is in engineering and technology adoption rather than a scientific one. At present, greatest needs are in the areas of integration, standardization, development of tools, and adoption by users. Further progress is still required. Quratulain4

Semantic Web Goals 1.Building models: quest for describing the world in abstract terms to allow for an easier understanding of complex reality. 2.Computing with knowledge: constructing reasoning machines that can draw meaningful conclusions from encoded knowledge. 3.Exchanging information: the transmission of complex information resources among computers that allows us to distribute, interlink, and reconcile knowledge on a global scale. 5

Model Building Model: simplified description of certain aspects of reality, use for understanding, structuring, or predicting parts of the real world. Plato (Greek philosopher) proposed answer to following questions. – What is reality? – Which things can be said to exist? – What is the true nature of things? And lead to a first major contribution in philosophical field now known as ontology. 6

Building Model Taxonomy: Hierarchical classification – e.g Classification of diseases Non-hierarchical classification – e.g Thesaurus (relationships such as synonyms and antonyms are not hierarchical) 7

Calculating with knowledge Domain-independent rules provide template- like ways for inferring knowledge All A are B. All B are C. inferred knowledge that All A are C. 8

Calculating with knowledge Goal of AI: build machines exhibiting human intelligence Amount of knowledge for basic AI applications is overwhelming. Transforming human knowledge to machine-processable form is difficult Inference techniques became too slow for medium or large-scale tasks Consequently: research focused on restricted domains Expert systems, rule-based systems for highly structured areas 9

Exchanging information Applications – – Online classified – Wikis, blogs, social networks, tagging Quratulain10

Semantic Web Technologies Following are necessary to achieve Semantic Web goals: – Explicit Metadata – Ontologies – Logic – Agents Quratulain11

Explicit Metadata Keyword based system identify the words An Intelligent agent might able to identify personnel of center. But it will have difficulty in distinguishing manager from secretary. The semantic Web approach is not the development of super-intelligent agents. Instead the purpose is to add information about content. The metadata capture part of the meaning of data, thus the term semantic in semantic web. Quratulain12

Add Metadata IBA FCS program Instructor: Quratulain Course: Semantic Web IBA FCS program Instructor: Quratulain Course: Semantic Web HTML: IBA FCS program Quratulain Semantic Web XML : 13Quratulain

Ontologies Most cited definition by T. R. Gruber: “An ontology is an explicit and formal specification of a conceptualization.” An ontology describes the domain of discourse includes terms and relationships between terms. In the context of web, ontologies provides shared understanding of a domain. Shared understanding overcome the difference in terminology. Quratulain14

Hierarchy Quratulain15

Ontology and Web Search Ontologies are useful for improving the accuracy of Web searches. – The search engines can refer to a precise concept in an ontology instead of collecting all pages. – If query fail to find any relevant documents, the search engine may suggest to the user a more general query. Ontology languages for the Web are XML, RDF, RDFS, OWL. Quratulain16

Logic Logic offers: – Formal language for expressing knowledge. – Well-understood formal semantics. – Automated reasoners can deduce (infer) conclusions from the given knowledge, thus making implicit knowledge explicit. For logic to be useful on Web – It must be usable in conjunction with other data. – It must be machine processable. Quratulain17

Logic and Agent Advantage of logic is – Provide explanations for conclusions by retracing series of inference steps. Explanation are important for the semantic Web because they increase user’s confidence in Semantic Web agents. Explanation will also be necessary for activities between agents. Quratulain18

Agents Agents are pieces of software that work autonomously. A personal agent on Web will receive some tasks and preferences, select certain choices, and give answer to the user. Not replace human users but provide choices. Agents uses all the technologies: metadata, ontologies, and logic. Quratulain19

Reading Assignment aics.pdf Quratulain20