RDF Kitty Turner

Current Situation there is hardly any metadata on the Web search engine sites do the equivalent of going through a library, reading every book, and allowing us to look things up based on the words in the text

What is RDF? general framework to describe any Internet resources by describing and interchanging metadata provides the basis for generic tools for authoring, manipulating, and searching machine-understandable data on the Web thereby promoting the transformation of the Web into a machine-processable repository of information

What is RDF? an XML application - utilizes the namespace facility - this allows RDF to scope and uniquely identify a set of properties (a schema) which can be accessed at the URI identified by the namespace - also inherits the language tag which enables support of multi-lingual metadata

Facts originally conceived as an extension of the content rating PICS (Platform for Internet Content Selection) Recommendation now a formal W3C Recommendation a 2 nd W3C Recommendation proposes a system where descriptions related to a particular purpose would constitute a class (much like OO); theses classes could fit into a hierarchy of classes with inheritance provides the building blocks for supporting the Semantic Web

Uses of RDF metadata resource discovery for search engines cataloging for describing content and content relationships available at a web site intelligent software agents to facilitate knowledge sharing content rating describing collections of pages that represent a single logical document describing intellectual property rights of Web pages

RDF Rules 1. a Resource is anything that can have a URI web pages, individual elements of XML docs, etc. 2. a Property is a Resource that has a name and can be used as a property any independent organization can invent them ex: Author or Title

RDF Rules 3. a Statement is a 3-part records consisting of Resource, Property and a value ex: “The Author of is Tim Bray.” 4. The abstract Properties are expressed in XML as follows: Tim Bray

A Bigger Example The Future of Metadata Jacky Crystal Metadata, RDF, Dublin Core

More Basics You can have multiple schemas (sets of properties) <RDF xmlns = " #" xmlns:DC = xmlns:AGLS = " > The Future of Metadata Jacky Crystal Metadata, RDF, Dublin Core Info Man’t -Internet

More Basics You can have complex values using properties as values Dr Jacky J Crystal Director Researcher

More Basics You can have the value be a literal which will not be interpreted Dr Jacky J Crystal DSTC 500 Street Australia

More Basics RDF can express collections of the same properties with Bag, Sequences (Seq) and Alternatives (Alt)

More Basics a Bag is a collection of multiple values for the same property - used instead of repeating the Property type Maddie Azzurii Corky Brown Jacky Crystal

More Basics a Seq is a collection of multiple values for a property where the order of the values is important Maddie Azzurii Corky Brown Jacky Crystal

More Basics an Alt is used when there is a choice of values available for a property which each value being valid but dependent on some factor. ftp://soft-sales.com.us/abc.exe ftp://soft-sales.com.au/abc.exe ftp://soft-sales.com.de/abc.exe ftp://soft-sales.com.uk/abc.exe

More Basics RDF allows statements to be made about other statements - useful when expressing properties of metadata

Example The Metadata Report Jacky Crystal $AUD

More Basics RDF has 2 types of syntax: 1. serialization: full expression seen in the examples above 2. abbreviated : values of the properties are expressed within XML tags - useful when including RDF in HTML documents so that no value is rendered in the Web browser - does have some limitations: the Properties are non- repeatable and the Property values can only be strings

Example of Abbreviated RDF <RDF xmlns = " #" xmlns:DC = " xmlns:AGLS = " > <Description about = " DC:Title = "The Future of Metadata" DC:Creator = "Jacky Crystal" DC:Date = " " DC:Subject = "Metadata, RDF, Dublin Core" AGLS:Function = "Info Management - Internet" />

More Basics a Resource can be a the value of a Property ex: a list of research papers that make up a collection for a conference Proceedings of the XML'98 Conf Jacky Crystal

More Basics RDF can describe individual properties within a collection of properties ex: to say that 5 of the papers list previously are all copyrighted by IEEE Copyright IEEE 1998

More Basics another alternative to the previous example Copyright IEEE 1998

More Basics RDF includes preliminary work on the definition of metadata schema which will define the meaning, characteristic and relationships of a set of properties the schema is based on the same model as the RDF syntax specification

Example of RDF schema <RDF xmlns = " xmlns:RDFS = " > Title The name given to the resource, usually by the Creator or Publisher Author or Creator The person or organisation primarily responsible for the intellectual content of the resource

More Basics RDF provides a model for metadata and a syntax so that independent parties can exchange and use it. BUT it doesn’t provide any Properties of its own The idea is that Properties will come in packages called Vocabularies. ex: basic bibliographic Properties will include Author, Title, Date, Publisher, etc.

RDF and XML RDF: because statements are simple, 3-part records, they are easy to handle and to use for looking up things even in large numbers - with the continuing growth of the Web, scalability is very important XML: isn’t scalable because - the order in which elements appear is significant which is anathema in the metadata world and very difficult to maintain with millions of data items - certain XML constructions are hard to handle