H. Weinberger - A. Frank 1 Internet Resources Discovery Metadata (3)

H. Weinberger - A. Frank1

Internet Resources Discovery

Metadata (3)


Contents of Metadata Lecture

1. Introduction to Metadata2. Interoperability of Metadata3. Evolution of Descriptive Metadata4. Web Descriptive Metadata5. Structured Metadata6. Semantic Web


Content

1. Introduction 2. Context and Meaning3. Web sites requirements:

challenges and possible solutions

4. Web document standards HTML and XML Understanding XML Understanding RDF


1 .Introduction

מידע-על מבניStructured metadata הוא מידע-על מובנה )פורמלי( מובן למכונה )מחשב(

מונחים נרדפים בשימוש: שפות סימון, שפות תחביר מתארות מבנה סימוןשפות (Structure) פורמט וFormat) )

בהם מוצג הטקסט..מידע-על מבני בדרך כלל נפרד מהתכנים שיטות ההבניה הנפוצות ביותר בשימוש הן ממשפחתSGML

:שהיא.(Markup specification)מערכת כללים לתיאור תחביר – SGMLמפרט מסוים שמוגדר באמצעות –

Document Type Definition .)DTD(


2 .Context & Meaning

“Sometimes my whole world seems out of context”


3. Web Sites Requirements

Standardize on logical views, not physical implementations.

Standard description of logical views available:– More than databases actually did.

Sites can interact with each other and with clients!


3.1 Challenges to Realize the Web’s Full Potential...

Find information intelligently.Interact with applications on

servers easily and efficiently.But: physical implementations

will vary from site to site.


3.2 Information retrieval and descriptive metadata

The need: exchange metadata from different schema.

The solution:– RDF: framework for syntax and structure – XML: representation language– DC: metadata schema


4.Web Document Standards

SGML - Standard Generalized Markup Language HTML - Hypertext Markup Language XML - Extensible Markup Language RDF - Resource Description Framework

SGML XML- structure

SGML app

HTML XML app

RDF- semantics

RDF app.


HTML

Began as a simple markup language for Web documents . Brought into closer compliance with SGML )HTML 2.0

includes an SGML DTD(. A DTD states what tags and attributes are used to describe

content in an SGML document, where each tag is allowed, and which tags can appear within other tags.

Common usage still flaunts SGML conventions.

HTML Structural elements:

גוף המסמך, פסקאות, כותרות, שורה חדשה, טבלה, רשימה– Document appearance

גופן, מירכוז וכיוצ"ב–


XML – What is it?

Extensible Markup LanguageAn XML document primarily consists of nested

hierarchy of elements with a single root. Elements can contain character data, child elements, or a mixture of both – and they can have Attributes.

An XML markup language is defined in a DTD )Document Type Definition(.

http://www.cs.ucl.ac.uk/staff/A.Finkelstein/syllabusresources.html

XML DTD declares:– Elements– Attributes


What is XML – what does it do

XML tags don’t describe user interface. There is no default presentation for each tag. They describe information.– XML has no special tags for titles or lists or

paragraphs or images. – It isn’t a presentation grammar. It is a way to

encode any information.


What is unique in XML vs. HTML

Tags may not overlap each other.Example of illegal XML:

– <Person><Name>Adam</Name><KeyPoint><Heading>XML provides a data bus</Heading> </Person><More>…</More> </KeyPoint>

Example of legal XML:– <Person>

<Name>Adam Bosworth</Name> <Title>General Manager</Title> <Age>42</Age></Person>


XML's suitability as a universal data format for the Web

Open standards and extensibility Separation of content, presentation,

linkingComputer platform and software

application neutrality, interoperabilityUnicode and data longevity Will XML DTDs or schemas replace

MARC?


XML

School

Root element

Child elements

XML examples


XML- Towards Semantic Web

XML: towards meta-grammer for inter-organizational communication around the Web.

XML schema is an emerging standard from W3C. XML schema is a language for defining the structure of XML document instances that belong to a specific document type.


XML DTDs Possibilities

Provide a formal and complete definition of an XML vocabulary.

Are sharable descriptions of a the structure of an XML document.

Are a way to validate specific instances of XML documents and constrain their content.

Are restricted to on DTD per document instance.

מערכתאפשר להגדיר DTD’s.של

מגדיר אלמנטיםבכל שסביר שצריך

.המסמכים ,לכאורהHTML הוא

שמערב DTDסוג של יסודות מבניים עם

.צורניים


Resource Description Framework (RDF)

שיטה באמצעותה ניתן לבצע חילופין של מידע-על: .: מודל מבני לביטוי תחבירכן–.: ציון סמנטיקה של מידע-עללא–

על, דוגמת -בסכמת מידעDC שלושה היבטים, קיימים:Semantic ההיבט הסמנטי מתאר כיצד להבין מושגים כמו :

Data, CreatorDC, לדוגמא, לציין שהכוונה במובן creatorכיצד להבין מושגים כמו

Syntax ההיבט התחבירי מפרט כיצד לבטא את המידע-על :. creatorלדוגמא: תאור המחבר ייעשה באמצעות האלמנט

Structureמבנה מגדיר יחסים בין אלמנטים של מידע-על : לדוגמא: יום, תאריך ושנה


RDF Objects

:משפט בשפה טבעית המלט )המחזה( של )סוג התייחסות( הוא המחבר )ערך( שייקספיר

)משאב מתואר(

Resources: Things described )Hamlet( Properties: Specific aspects )attributes,

relations( used to describe a resource )…Author(

Statements: A specific resource + a named property + the value of that property for that resource )…Shakespeare(


RDF Structural Model

Resource Property type Value Hamlet creator Shakespeare

A different metadata scheme might use author in place of creator, and ,might use type for a different meaning, therefore, the RDF markup make explicit that this metadata is expressed in the DC schema, as follows:

<DC:creator>Shakespeare</DC:creator><DC:type>play</DC:type>A more precise Hamlet description, using imaginary URL:

<RDF:RDF><RDF:description RDF:about=http://hamlet.org/>

<DC:creator>Shakespeare</DC:creator><DC:type>play</DC:type>

<RDF:description><RDF:RDF>


RDF Application Capabilities

in resource discovery to provide better search engine capabilities.

in cataloging for describing the content and content relationships.

by intelligent software agents to facilitate knowledge sharing and exchange.

in content rating in describing collections of pages that represent a single logical "document“.

for describing intellectual property rights of Web pages.


Web Metadata & Web Future

Searching on the web will become easier as search engines have more information available. Searching can be more focused. Doors will also be opened for automated software agents to roam the web.

The web of today, the vast unstructured mass of information, may in the future be transformed into something more manageable - and thus something far more useful.


References

XML Adam Bosworth, XML:A Revolution Unfolds Cover, robin, Extensible Markup Language )XML( http://www.oasis-open.org/cover/xml.html W3C Extensible Markup Language )XML( 1.0 http://

www.xml.com/axml/axml.html Ronald Bourret, Declaring Elements and Attributes in an XML

DTD http://www.rpbourret.com/xml/xmldtd.htm XML DTD Example

http://www.cs.ucl.ac.uk/staff/A.Finkelstein/syllabusresources.html

RDF Site Summary )RSS(

http://groups.yahoo.com/group/rss-dev/files/specification.html


Contents of Metadata Lecture

1. Introduction to Metadata2. Interoperability of Metadata3. Evolution of Descriptive Metadata4. Web Descriptive Metadata5. Structured Metadata6. Semantic Web


What is the Semantic Web? (1)

"The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation."

Tim Berners-Lee, James Hendler, Ora Lassila, Consistent logical web of data = Semantic

Web


What is the Semantic Web? (2)

“The Web is about links; the Semantic Web is about the relationships implicit in those links.” Dan Brickley

Semantic Web is part of the W3C technology and society domain. – Manage the development of enabling standards

and technologies. The Semantic Web is a web whose content

can be processed by computers. … an infrastructure for supplying the Web with formalized knowledge…” Jerome Euzenet, EU-NSF 2002


Research Organizations

W3CEuropean Union Future Emergent

Technology program )EU-FET(National Science Foundation )NSF(


Metadata & the Semantic Web

Meta-data is the fundamental building block of the Semantic Web. Mikael Nilsson et al.

Metadata architecture - envisioned as an "ecosystem" of ever-evolving interpretations layered upon objects as they are created, used and reused. Scott Wilson, CETIS staff )centre for educational technology interoperability standards(


The Current Web in Context

Web is a set of Resources and Links Resources identified by URI's Uniform Resource Identifiers.

To a user, this has become an exciting world To a machine, however, very little machine-readable information is avaliable.

The meaning of the documents is clear to those with a grasp of )normally( English. The significance of the links is only evident from the context around the anchor.


The Semantic Web - A Simple Extension to

(1) the Current Web


The Semantic Web - A Simple Extension to

(2) the Current Web

H. Weinberger - A. Frank 1 Internet Resources Discovery Metadata (3)

Documents

metadata schema slide

web descriptive metadata

context slide

semantic web slide

exchange metadata

interoperability of

contents of metadata

structure xml