Module 2b: Modeling Information Objects and Relationships IMT530: Organization of Information Resources Winter, 2007 Michael Crandall.
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Module 2b: Modeling Information Objects and Relationships IMT530: Organization of Information Resources Winter, 2007 Michael Crandall
IMT530A Organization of Information Resources2 Recap Information storage and retrieval systems (ISARs) are part of a larger knowledge system Within an ISAR, two inputs (user needs and entities) are combined to produce an answer for the user’s question To make that happen, both user’s queries and information entities need to be represented in some way
IMT530A Organization of Information Resources3 Module 2b Outline Models The entity-relationship model for database design Resource Description Framework for the web Syntax vs. semantics Ontologies and their place
IMT530A Organization of Information Resources4 What is a Model? A model represents a particular view of reality through a systematic set of rules –As you’ve seen with vocabularies, a representation is only that, not reality In information systems, we are attempting to represent objects and their relationships –This can become very complex, very quickly –A way to manage this complexity is critical for success Models allow multiple systems to interact and share information more effectively –Think of last week’s slide showing MSWeb’s search service- outside sources sharing the same model can provide much richer information to the system (and ultimately the users)
IMT530A Organization of Information Resources5 Sources of Models Database world –Entity-relationship model Programming world –Object oriented programming Information science world –Functional Requirements for Bibliographic Records –Dublin Core Web world –Resource Description Framework –Ontology Web Language
IMT530A Organization of Information Resources6 Database Modeling Chen developed concept of entities and relationships –Entities are “things which can be described” –Relationships are “associations between entities” –These have attributes which are instantiated in values Allows description of complex spaces through diagrams showing how entities relate to other entities (tuples) –Represented in tables within databases Essential in relational database modeling
IMT530A Organization of Information Resources7 Example of E-R Model From Chen, 1985
IMT530A Organization of Information Resources8 How RDF Works RDF is based on the idea that –Things being described (the Subject) –Have properties (the Predicate), –Which have values (the Object) And that resources can be described by making statements that specify those properties and values (triples) RDF models statements as nodes and arcs in a graph. In this notation, a statement is represented by: –a node for the subject –a node for the object –an arc for the predicate, directed from the subject node to the object node.
IMT530A Organization of Information Resources9 How RDF Works This is done using URIs (Uniform Resource Identifiers) that can be created to refer to anything that needs to be referred to in a statement, including –network-accessible things, such as an electronic document, an image, a service (e.g., "today's weather report for Los Angeles"), or a group of other resources. –things that are not network-accessible, such as human beings, corporations, and bound books in a library. –abstract concepts that do not physically exist, such as the concept of a "creator".
IMT530A Organization of Information Resources10 An Example http://www.example.org/index.html has a creator whose value is John Smith could be represented by an RDF statement having: –a subject http://www.example.org/index.html –a predicate http://purl.org/dc/elements/1.1/creator –and an object http://www.example.org/staffid/85740
IMT530A Organization of Information Resources11 Example of RDF Model Figure 1: An RDF Graph Describing Eric Miller
IMT530A Organization of Information Resources12 RDF in XML Eric Miller Dr.
IMT530A Organization of Information Resources13 Syntax vs. Semantics Note that models are distinct from the language used to represent them –An RDF model can be written in XML, but is independent of the language The reason XML becomes important is for machine to machine communication –Allows recognition of structures and semantics in a common way, promoting interoperability at the syntax level Semantics are controlled by the model –Different models may not communicate even if you’re using XML –So defining and standardizing your semantic model is critical for true interoperability
IMT530A Organization of Information Resources14 Ontologies Semantic web is next step to embed semantics in syntax- but you need to model namespaces to do this Rich namespaces are being modeled through ontologies- an extension of classification theory that includes many more relationship types Qin and Paling on advantages of ontology –Higher levels of conception of descriptive vocabulary –Deeper semantics for class/subclass and cross-class relationships –Ability to express such concepts and relationships in a description language –Reusability and share-ability of the ontological constructs in heterogeneous systems OWL (Web Ontology Language) is current favorite tool (http://www.w3.org/TR/owl-features/)http://www.w3.org/TR/owl-features/
IMT530A Organization of Information Resources15 Ontology Example http://www.aiai.ed.ac.uk/project/enterprise/enterprise/ontology.html
IMT530A Organization of Information Resources16 Questions?? And then a break….
IMT530A Organization of Information Resources17 Exercise 2b Assemble your group Spend 45 minutes working through the examples in Exercise 2b Ask questions and talk!!! Be sure to hand in completed work at the end of class for credit!!!
IMT530A Organization of Information Resources18 Example of Integration <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:eg="http://example.org/foovocab#" xmlns:foaf="http://xmlns.com/foaf/0.1/"> Alice Bob <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:eg="http://example.org/foovocab#" xmlns:foaf="http://xmlns.com/foaf/0.1/"> Bob 241021fb0e6289f92815fc210f9e9137262c252e Carol <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:eg="http://example.org/foovocab#" xmlns:foaf="http://xmlns.com/foaf/0.1/"> Alice Bob 241021fb0e6289f92815fc210f9e9137262c25 2e Carol Contributed by Oknam Park
IMT530A Organization of Information Resources19 Modeling Wrapup One model will not fit all needs More and more, integration of web models with database and programming models is becoming important Each will provide a different view of the world you are trying to manage Finding linkages for interoperability is the big challenge We’ll look next week at some current attempts in this area Think about how you would approach these problems and see how it fits what you read
IMT530A Organization of Information Resources20 Next Week We’ll hear from a guest speaker about commercial use of ontologies We’ll dive into metadata schemas and schemes and the world of standards Remember to read next week’s assignments BEFORE class Have a great weekend!!