metadata for web-based information management dickson k. w. chiu senior member, ieee & acm...
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Metadata for Web-based Information Management
Dickson K. W. CHIUSenior Member, IEEE & ACMDickson Computer Systems
Hong Kong [email protected],
Poon, Joe Kit Man Lam, Wai ChunTse, Chi Yung
Sui, William Hi TaiPoon, Wing Sze
Department of Computer Science,
University of Hong Kong
Ontology Dickson Chiu - update 2009 Metadata - 2
Towards a Semantic Web
WWW is an impressive success: amount of available information (> 1 Giga-page) number of human users (> 200 Mega-user)
The current Web represents information using natural language (English, Hungarian, Chinese,…) graphics, multimedia, page layout
Humans can process this easily can deduce facts from partial information can create mental associations are used to various sensory information
(well, sort of… people with disabilities may have serious problems on the Web with rich media!)
Ontology Dickson Chiu - update 2009 Metadata - 3
Need for understanding Web info Tasks often require to combine data on the Web:
hotel and travel infos may come from different sites searches in different digital libraries etc.
Again, humans combine these information easily even if different terminologies are used!
Ontology Dickson Chiu - update 2009 Metadata - 4
What is the Problem?
Consider a typical web page:
Markup comprise rendering
information (e.g., font size and colour)
Hyper-links to related content
Semantic content is accessible to humans but not (easily) to computers…
Ontology Dickson Chiu - update 2009 Metadata - 5
What information can we see…WWW2002The eleventh international world wide web conferenceSheraton waikiki hotelHonolulu, hawaii, USA7-11 may 20021 location 5 days learn interactRegistered participants coming fromaustralia, canada, chile denmark, france, germany, ghana, hong kong,
india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire
Register nowOn the 7th May Honolulu will provide the backdrop of the eleventh
international world wide web conference. This prestigious event …Speakers confirmedTim berners-lee Tim is the well known inventor of the Web, …Ian FosterIan is the pioneer of the Grid, the next generation internet …
Ontology Dickson Chiu - update 2009 Metadata - 6
Information a machine may see…
…
… …
Ontology Dickson Chiu - update 2009 Metadata - 7
Solution: XML markup with “meaningful” tags?
<name> </name><location>
</location>…
How about…<conf>
</conf>
<place>
</place>
Then how about…< 会议>
</会议 >
< 地点>
</地点 >
Ontology Dickson Chiu - update 2009 Metadata - 8
What Is Needed?
A resource should provide information about itself
also called “metadata” (data about data) Metadata capture part of the meaning of data metadata should be in a machine processable format agents should be able to “reason” about (meta)data metadata vocabularies should be defined
Ontology Dickson Chiu - update 2009 Metadata - 9
What Is Needed (Technically)?
To make metadata machine processable, we need:
unambiguous names for resources (URIs) a common data model for expressing metadata (RDF)
and ways to access the metadata on the Web common vocabularies (Ontologies)
The “Semantic Web” is a metadata based infrastructure for reasoning on the Web
It extends the current Web (and does not replace it)
Ontology Dickson Chiu - update 2009 Metadata - 10
Ontology in Philosophy - a philosophical discipline—a branch of philosophy that deals with the nature and the organization of reality
Science of Being (Aristotle, Metaphysics, IV, 1) studies being or existence as well as the
basic categories thereof trying to find out what entities and what
types of entities exist has strong implications for the conceptions of reality.
Ontology: Origins and History
Ontology Dickson Chiu - update 2009 Metadata - 11
An ontology is an engineering artifact [Neches91]: defines basic terms and relations comprising the vocabulary
of a topic area the rules for combining terms and relations to define extensions to
the vocabulary “An explicit specification of a conceptualization” [Gruber93] Formal specification of a shared conceptualization (of a certain
domain) [Borst 97]: Shared understanding of a domain of interest Formal and machine manipulable model of a domain of interest
Ontology in Computer Science
Ontology Dickson Chiu - update 2009 Metadata - 12
Ontology Elements Concepts (classes) + their hierarchy Concept properties (slots / attributes) Property restrictions (type, cardinality, domain, etc.) Relations between concepts (disjoint, equality, etc.) Instances
E-R diagram / UML diagram ??? Note: “Property” “Slot” “Relation” “Relationtype”
“Attribute” Semantic link type”
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Ontology Languages
RDF Schema RDF is a data model for objects and relations between
them RDF Schema is a vocabulary description language Describes properties and classes of RDF resources Provides semantics for generalization hierarchies of
properties and classes
Ontology Dickson Chiu - update 2009 Metadata - 14
Web Ontology Languages (2)
OWL A richer ontology language relations between classes
e.g., disjointness cardinality
e.g. “exactly one” richer typing of properties characteristics of properties (e.g., symmetry) Logic
BOTH are standards of www.w3.org
Ontology Dickson Chiu - update 2009 Metadata - 15
History of the Semantic Web Web was “invented” by Tim Berners-Lee (amongst others), a
physicist working at CERN TBL’s original vision of the Web was much more ambitious than
the reality of the existing (syntactic) Web:
TBL (and others) have since been working towards realising this vision, which has become known as the Semantic Web
E.g., article in May 2001 issue of Scientific American…
“... a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of people's thoughts, interactions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management of large organizations.”
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Adding “Semantics” External agreement on meaning of annotations
E.g., Dublin Core (http://dublincore.org/) Agree on the meaning of a set of annotation tags
Problems with this approach Inflexible Limited number of things can be expressed
Use Ontologies to specify meaning of annotations Ontologies provide a vocabulary of terms New terms can be formed by combining existing ones Meaning (semantics) of such terms is formally specified Can also specify relationships between terms in multiple
ontologies
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Berner-Lee’s Architecture
Data Exchange
Semantics+reasoning
Relational Data?
?
???
???
???
• Relationship between layers is not clear• OWL DL extends “DL subset” of RDF
Ontology Dickson Chiu - update 2009 Metadata - 18
The Role of Ontologies on the Web
Ontologies provide a shared understanding of a domain: semantic interoperability
overcome differences in terminology mappings between ontologies
Ontologies are useful for the organization and navigation of Web sites
Ontologies are useful for improving the accuracy of Web searches
search engines can look for pages that refer to a precise concept in an ontology
Web searches can exploit generalization/ specialization information
If a query fails to find any relevant documents, the search engine may suggest to the user a more general query.
If too many answers are retrieved, the search engine may suggest to the user some specializations.
General e-business automation based on understanding web resource in order to facilitate intelligent (software agent) processing
Ontology Dickson Chiu - update 2009 Metadata - 19
Case study: Use of Ontology in an e-Marketplace
D.K.W. Chiu, J.K.M. Poon, W.C. Lam, C.Y. Tse, W.H.T. Siu, W.S. Poon. How Ontologies Can Help in an E-marketplace, European Conference on Information Systems 2005 (ECIS 2005), May 2005
Semantic Web vision is probably too ambitious A more realistic current application that has a
potential to become a killer application
Ontology Dickson Chiu - update 2009 Metadata - 20
Motivation
Compare some general-purposed e-Marketplaces (auction based)
e-Bay (HK): www.ebay.com.hk Yahoo Auction (HK): auctions.yahoo.com.hk Taobao owned by Alibaba.com: http://www.taobao.com
(See also Alibaba.com: http://china.alibaba.com/) Compare special-purposed e-Marketplaces
Airtickets: http://www.qunar.com/ Finding friends (!): http://hk.personals.yahoo.com/
Which one is better? Why? Key issue => capturing and applying domain
knowledge
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What is an e-Marketplace?
Buyers
Supplierse-Marketplace
Aggregate requests from Buyers, contactpotential Suppliers,
match Suppliersand Buyers, exchange
bids and offers,generate e-Contract
Repository
Ontologies and Concepts
e-Negotiation dataAgreements- …
bids
bids
offers
offers
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Problem Statements
Are there currently significant practical use of the Ontology from Semantic Web?
Match-making and beyond Software requirement engineering / negotiation Model and solve practical problems with CS &
ICT Cross-over multi-disciplinary research
IJSSOE: Dickson Chiu, Editor-in-chiefhttp://www.igi-global.com/journals/details.asp?id=34268
Ontology Dickson Chiu - update 2009 Metadata - 23
Example Ontology Clothing and Sales Negotiation
Quantity
PurpleRed
Discount
Total Amount
Refunding Policy
ColorSize
Appearance
Clothing
Unit Cost
Payee
Insured Amount Insurer Premium
{unordered} attributes: deposit, installment, pay-upon-delivery, ...
{unordered} attributes: brick red, crimson, ...
{ordered} attributes: small, medium, large, extra-large
{unordered} attributes: light purple, magenta, ...
Delivery Date
Sale Order
**
Delivery
Shipping Cost
Payment Terms
Insurance
Ontology Dickson Chiu - update 2009 Metadata - 24
Objective and Solution Approach How to elicit negotiation requirements? Semantic Web
=> Ontologies => help negotiators’ mutual understanding of issues, alternatives, and tradeoffs
Address semantic requirements of negotiation Reduce cost and improve effectiveness of negotiation
(avoid combinatorial explosion of issues) Development of an effective and efficient negotiation
plan Applications: e-Marketplace, Web-service
negotiation, agent negotiation, requirement negotiation…
Ontology Dickson Chiu - update 2009 Metadata - 25
Semantic basede-Marketplace Conceptual Model
Accepted Alternative ValueAccepted Offer
Trader
Recommendation
Matchmaking
Negotiation
Offer
Auxiliary Concept
IssueTask1..n
1..n 1..n
1..n
1
1..n1
Decision Plan
11
Ontology
nn
Alternative Value1..n1..n
Concept
1..n
1..n
1..n
1..n
1..n
1
1
n
1..n
nn
Base Concept
n
n
2..n
1..n
1..n
1..n
1..n
1
evaluates
drives1
1
1
nformulates
indivisibly relates to
nn
precedesn
n
1..n
resolves1..n1
1..n
1maps to
Ontology Dickson Chiu - update 2009 Metadata - 26
Overall e-Negotiation Process Design Methodology
Trader select agreed relevant ontologies
Trader identify issues
System maps issues into ontology concepts
System derive concept relations
System creation of agreement
Trader post (revised) preferences as offer
Trader product selection
[reject all matches/recommendations]
[accept offer]
[need to identify new issues]
System performs recommendation
System supported trader negotiation
[all issues are resolved]
[quit negotiation]
[need to identify new issues]
[need to revise tradeoff model]
[negotiation target chosen]
System check consistency of issues & concepts
[not consistent]
System performs matchmaking
[match not found]
[match found]
Trader specifies alternative values of issues
[trader change requirements]
System identifies alternatives
[consistent]
System formulate decision plan
Requirements elicitation phase
Decision phase
for each collection of co-related
issue
Requirementselicitationphase
Decisionphase
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Requirement Elicitation Methodology
1. Traders select agreed ontology.2. Traders relate requirements to concepts in the selected ontology.3. System checks dependencies of concepts that constitute all the
requirements from the (refined) ontology map. Mutually dependent clusters of concepts determine the indivisible groups of requirements that have to be considered together so that effective tradeoff can be evaluated.
4. The system checks the consistency of all the concepts, issues, and their dependencies (Cheung et al. 2002).
5. For a consistent plan, the system can proceed to elicit the possible alternatives; otherwise we have to re-iterate from step 3.
6. According to the dependencies, the system can formulate a precedence graph of the requirements and requirements groups. Based on the precedence graph, an efficient decision plan can be determined.
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Decision Phase Methodology The system
searches for the matching offers based on the trader’s preference attempt to rank them for the trader to choose
Trader may accept any matched offers or change his reservation price and attempt a negotiation with those
offers in order to seek for a more favorable one. If no matching offers are found, the system identifies near
misses and also attempts to rank them for the trader to choose. Trader change his mind to accept a near miss
or choose a near miss for negotiation. During negotiation, the system supports the user to make and
evaluate offers / counter-offers based on the decision plan (from previous slide) in a negotiation session as follows (Chiu et al. 2005).
Should new requirement issues arise in the decision phase (say, due to incomplete specification), the trader can we can go back to analyze the new issue and its relationships to the existing ones.
In real-life, the formulation of a decision plan may involve several iterations. This reflects the traders may not be able to understand all the inter-relationships among the issues in one shot.
Ontology Dickson Chiu - update 2009 Metadata - 29
Understanding Requirements from Ontologies
Perform graph search algorithm on the semantic map
Key requirements are preliminary identified in the first round (e.g., unit price, quantity)
For each identified requirement issue, check if an issue can be mapped directly to a concept. If not, see if an issue can be refined into a set of more
specific concepts a cost is refined into constituent costs that sum up to
it. Incomplete Ontologies
Introduce new concepts into the ontology map Relate it with to existing ones
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Understanding Requirements from Ontology (Cont)
Perform graph search algorithm on the semantic map For each identified concept c,
Examine every un-visited node n adjacent to c in the ontology map.
For each such node n, see if the new concept is relevant to the negotiation problem.
Repeat until no more related new concepts can be identified.
Only after successful deal do we need to consider combining newly identified working concepts back to more concise real-life objects in specifying a agreement E.g., component costs need not shown to business
partner
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Understanding Dependencies of Requirements from Ontologies
Functional dependency borrowed from fundamental relational database
concepts motivate this research The alternative for an issue is determined by the
alternatives(s) of other issue(s). E.g., delivery date and quantity -> cost of production
Computational dependency more obvious type of functional dependency hardwired computational formula E.g., insurance amount = percentage * cost of goods.
Ontology Dickson Chiu - update 2009 Metadata - 32
Understanding Dependencies of Requirement from Ontology
Requirement dependency (constraint satisfaction) Only after the determinant value is known can viable
alternatives be determined. E.g., whether a customer may pay by credit card,
bank draft, or remittance is evaluated according to the total amount.
Classification dependency A special type of requirement dependency in which
the classification of another issue is dependent on the outcome of an agreed issue.
E.g., customer tiering
Ontology Dickson Chiu - update 2009 Metadata - 33
Indivisible Requirement Components for Tradeoff Evaluation
Indivisible Components of Issues Cyclic dependencies among the concepts Tradeoff Evaluation
Topological sort of semantic graph gives negotiation plan
Determine Size
Determine Color
Determine Refund Policy
Determine Unit Cost, Quantity & Delivery Date
Determine Payment Terms
Determine Shipping Cost and Payee
Determine Insurance Premium, Insured Amount & Insurer
Determine Discount
Compute Total Amount
Ontology Dickson Chiu - update 2009 Metadata - 34
Understanding Possible Requirement Alternatives from Ontology
Alternative for requirements are often in discrete values cannot be expressed in numerical values not quantized in normal practices because of difficulties
in recognizing them, e.g., color for simplicity and convenience (size => S, M, L, XL)
The elicitation of options is streamlined when a complicated issue is decomposed into concepts(appearance => size + color + shapes)
Ontology provide explicit ordering of them (size => S < M < L < XL) implicit ordering
inheritance (“is-a”) hierarchies composition hierarchies
Ontology Dickson Chiu - update 2009 Metadata - 35
Exploring more trading opportunities
from Ontology
Improve the accessibility of automated agents to match functional specification
Intelligent software agents could represent buyers or sellers
e-marketplace acts as “broker” Consider shared ontology attributes and
constraints Map for cross-sale Group buyers or sellers together for higher
market efficiencies Better hints for data mining
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System Implementation Architecture
Multiplatform Support Subsystem
WAP Gateway
SMS Gateway
Internet Messenger
Web Server
e-Negotiation Executing Subsystem
e-Negotiation Session Manager
Ontology Generator
e-Negotiating Matching Subsystem
e-Negotiation Process Generator
Task Organizer
Issue Dependency Editor
issuedependency
taskdependency
Ontology Maintenance Subsystem
Ontology Editor
Search Engine
Criteria & Issues Editor
ontology
CriteriaIssue
bids & offers e-Negotiation process
ontologyIssue
ontology
e-Negotiation process
revised ontology, issues
existing ontology
e-Negotiation Data & Repository
MultiplatformDevices
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OWL Listing<owl:Ontology rdf:about="#Clothing"> <rdfs:comment>Sample Clothing
Ontology</rdfs:comment> <owl:Class rdf:ID="Clothing" /> <owl:Class rdf:ID="Appearance" /> <owl:Class rdf:ID="Color"> <rdfs:subClassOf rdf:resource="#Appearance" /> ... </owl:Class> <owl:ObjectProperty rdf:ID="hasAppearance"> <rdfs:domain rdf:resource="#Clothing" /> <rdfs:range rdf:resource="#Appearance" /> </owl:ObjectProperty> <owl:ObjectProperty rdf:ID="hasColor"> <rdfs:subPropertyOf
rdf:resource="hasClothAppearance" /> <rdfs:range rdf:resource="#Color” /> ... </owl:ObjectProperty> <owl:DatatypeProperty rdf:ID="size"> <!-- Enumeration --!> <rdfs:domain rdf:resource="#Appearance"/> <rdfs:range> <owl:DataRange> <owl:oneOf> <rdf:List>
<rdf:rest> <rdf:List> <rdf:rest><rdf:List> <rdf:rest><rdf:List>
<rdf:rest rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#nil"/>
<rdf:first rdf:datatype="http://www.w3.org/2001/XMLSchema#string">Small</rdf:first></rdf:List></rdf:rest>
<rdf:first rdf:datatype="http://www.w3.org/2001/XMLSchema#string">Medium</rdf:first></rdf:List></rdf:rest>
<rdf:first rdf:datatype="http://www.w3.org/2001/XMLSchema#string">Large</rdf:first></rdf:List></rdf:rest>
<rdf:first rdf:datatype="http://www.w3.org/2001/XMLSchema#string">Extra Large</rdf:first></rdf:List>
</owl:oneOf></owl:DataRange></rdfs:range> </owl:DatatypeProperty> <owl:Class rdf:ID=" UnitCost"> … <owl:equivalentClass> <!-- unit cost depends on appearance --> <owl:Restriction> <owl:someValuesFrom
rdf:resource="#Appearance" /> </owl:Restriction> </owl:equivalentClass></owl:Class>…</owl:Ontology>
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SummaryFunction Traditional e-marketplace problem Contributions of Ontology
Match-making
Match-making is often ineffective because of the rigid definition of products of limited attributes.
Shared and agreed ontology provides common, flexible, and extensible definitions of products and requirements for match-making and subsequent business processes
It is difficult to specify complex product requirements because the relationships among attributes and values are ignored.
Complicated requirements can be decomposed into simple concepts for streamlining the elicitation of options
User interactions are limited to mainly manually, which is time consuming.
Accessible by automated agents through Semantic Web specifications for more business opportunities
Recom-mendation
Recommendations are often only possible within the same category.
Ontology helps elicit alternatives for recommendation.
Pre-set formulae for every type of product are needed for evaluation.
Ontology help recommendation by evaluating offers in terms of flexible overall scaling
Cross-sale and grouping of buyers and sellers with similar requests are difficult.
Matching grouping of buyers and sellers as well as cross-sale possible by inference with the ontology.
Negotiation No implicit ordering of alternatives. Implicit ordering of alternatives is elicited via inheritance.
Manual negotiation or inadequate negotiation support cause inefficient process and ineffective recognition.
Machine understandable semantics facilitate negotiation and automatic configuration of products and services as specified.
Ontology Dickson Chiu - update 2009 Metadata - 39
Conclusions Formulation of negotiation plan with maturing of
Semantic Web technologies Elicitation of negotiation issues, issue dependencies,
tradeoff, and alternatives Control the openness of issues Our algorithm verifies the completeness of elicited
negotiation requirements Negotiation processes are properly guided, recorded,
and managed For e-commerce activities are usually more structural
and repeatable (as opposed to political negotiations) Ontologies and plans are therefore reusable Negotiation automation with agents / integration with
EIS
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Future Work
Formal models Elicitation of semantic distances enhancement of ontology-based matchmaking and
recommendation algorithms ontology-based cross-sale and up-sale grouping of buyers and sellers for combined
quantity deals mobile clients and constraint-based requirement
specification
Ontology Dickson Chiu - update 2009 Metadata - 41
Question and Answer
Thank you!Email: [email protected]