Title: Internet Engineering Course
1Internet Engineering Course
- Semantic Web,
- Web Services,
- Semantic Web Services
2Agenda
- Vision of Next Generation Web Technology
- Semantic Web
- Todays Web
- The Semantic Web Impact
- Semantic Web Technologies
- A Layered Approach
- Web Services
- Why Web Services?
- Enabling Technologies
- Web Service Composition
- Main Issues concerning the composition
- Semantic Web Services
3Vision of Next Generation Web Technologies
- 500 million users
- more than 3 billion pages
WWW URI, HTML, HTTP
Static
3
4Vision of Next Generation Web Technologies
- Serious Problems in
- information finding,
- information extracting,
- information representing,
- information interpreting and
- and information maintaining.
WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
4
5Vision of Next Generation Web Technologies
Web Services UDDI, WSDL, SOAP
Dynamic
- Bringing the computer back as a device for
computation
WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
5
6Vision of Next Generation Web Technologies
- Bringing the web to its full potential
Semantic Web Services
Web Services UDDI, WSDL, SOAP
Dynamic
WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
6
7Semantic Web
8Semantic Web Outline
- Todays Web
- The Semantic Web Impact
- Semantic Web Technologies
- A Layered Approach
9Todays Web
- Most of todays Web content is suitable for human
consumption - Even Web content that is generated automatically
from databases is usually presented without the
original structural information found in
databases - Typical Web uses today peoples
- seeking and making use of information, searching
for and getting in touch with other people,
reviewing catalogues of online stores and
ordering products by filling out forms
10Keyword-Based Search Engines
- Current Web activities are not particularly well
supported by software tools - Except for keyword-based search engines (e.g.
Google, AltaVista, Yahoo) - The Web would not have been the huge success it
was, were it not for search engines
11Problems of Keyword-Based Search Engines
- High recall, low precision.
- Low or no recall
- Results are highly sensitive to vocabulary
- Results are single Web pages
- Human involvement is necessary to interpret and
combine results - Results of Web searches are not readily
accessible by other software tools
12The Key Problem of Todays Web
- The meaning of Web content is not
machine-accessible lack of semantics - It is simply difficult to distinguish the meaning
between these two sentences - I am a professor of computer science.
- I am a professor of computer science,
- you may think. Well, . . .
13The Semantic Web Approach
- Represent Web content in a form that is more
easily machine-processable. - Use intelligent techniques to take advantage of
these representations. - The Semantic Web will gradually evolve out of the
existing Web, it is not a competition to the
current WWW
14Semantic Web Outline
- Todays Web
- The Semantic Web Impact
- Semantic Web Technologies
- A Layered Approach
15The Semantic Web Impact Knowledge Management
- Knowledge management concerns itself with
acquiring, accessing, and maintaining knowledge
within an organization - Key activity of large businesses internal
knowledge as an intellectual asset - It is particularly important for international,
geographically dispersed organizations - Most information is currently available in a
weakly structured form (e.g. text, audio, video)
16Limitations of Current Knowledge Management
Technologies
- Searching information
- Keyword-based search engines
- Extracting information
- human involvement necessary for browsing,
retrieving, interpreting, combining - Maintaining information
- inconsistencies in terminology, outdated
information. - Viewing information
- Impossible to define views on Web knowledge
-
17Semantic Web Enabled Knowledge Management
- Knowledge will be organized in conceptual spaces
according to its meaning. - Automated tools for maintenance and knowledge
discovery - Semantic query answering
- Query answering over several documents
- Defining who may view certain parts of
information (even parts of documents) will be
possible.
18The Semantic Web Impact B2C Electronic
Commmerce
- A typical scenario user visits one or several
online shops, browses their offers, selects and
orders products. - Ideally humans would visit all, or all major
online stores but too time consuming - Shopbots are a useful tool
19Limitations of Shopbots
- They rely on wrappers extensive programming
required - Wrappers need to be reprogrammed when an online
store changes its outfit - Wrappers extract information based on textual
analysis - Error-prone
- Limited information extracted
20Semantic Web Enabled B2C Electronic Commerce
- Software agents that can interpret the product
information and the terms of service. - Pricing and product information, delivery and
privacy policies will be interpreted and compared
to the user requirements. - Information about the reputation of shops
- Sophisticated shopping agents will be able to
conduct automated negotiations
21The Semantic Web Impact B2B Electronic Commerce
- Greatest economic promise
- Currently relies mostly on EDI
- Isolated technology, understood only by experts
- Difficult to program and maintain, error-prone
- Each B2B communication requires separate
programming - Web appears to be perfect infrastructure
- But B2B not well supported by Web standards
22Semantic Web Enabled B2B Electronic Commerce
- Businesses enter partnerships without much
overhead - Differences in terminology will be resolved using
standard abstract domain models - Data will be interchanged using translation
services. - Auctioning, negotiations, and drafting contracts
will be carried out automatically (or
semi-automatically) by software agents
23Semantic Web Outline
- Todays Web
- The Semantic Web Impact
- Semantic Web Technologies
- A Layered Approach
24Semantic Web Technologies
- Explicit Metadata
- Ontologies
- Logic and Inference
- Agents
25On HTML
- Web content is currently formatted for human
readers rather than programs - HTML is the predominant language in which Web
pages are written (directly or using tools) - Vocabulary describes presentation
26An HTML Example
- lth1gtAgilitas Physiotherapy Centrelt/h1gt
- Welcome to the home page of the Agilitas
Physiotherapy Centre. Do - you feel pain? Have you had an injury? Let our
staff Lisa Davenport, - Kelly Townsend (our lovely secretary) and Steve
Matthews take care - of your body and soul.
- lth2gtConsultation hourslt/h2gt
- Mon 11am - 7pmltbrgt
- Tue 11am - 7pmltbrgt
- Wed 3pm - 7pmltbrgt
- Thu 11am - 7pmltbrgt
- Fri 11am - 3pmltpgt
- But note that we do not offer consultation during
the weeks of the - lta href". . ."gtState Of Originlt/agt games.
27Problems with HTML
- Humans have no problem with this
- Machines (software agents) do
- How distinguish therapists from the secretary,
- How determine exact consultation hours
- They would have to follow the link to the State
Of Origin games to find when they take place.
28A Better Representation
- ltcompanygt
- lttreatmentOfferedgtPhysiotherapylt/treatmentOffered
gt - ltcompanyNamegtAgilitas Physiotherapy
Centrelt/companyNamegt - ltstaffgt
- lttherapistgtLisa Davenportlt/therapistgt
- lttherapistgtSteve Matthewslt/therapistgt
- ltsecretarygtKelly Townsendlt/secretarygt
- lt/staffgt
- lt/companygt
29Explicit Metadata
- This representation is far more easily
processable by machines - Metadata data about data
- Metadata capture part of the meaning of data
- Semantic Web does not rely on text-based
manipulation, but rather on machine-processable
metadata
30Ontologies
- The term ontology originates from philosophy
- The study of the nature of existence
- Different meaning from computer science
- An ontology is an explicit and formal
specification of a conceptualization
31Typical Components of Ontologies
- Terms denote important concepts (classes of
objects) of the domain - e.g. professors, staff, students, courses,
departments - Relationships between these terms typically
class hierarchies - a class C to be a subclass of another class C' if
every object in C is also included in C' - e.g. all professors are staff members
-
32Further Components of Ontologies
- Properties
- e.g. X teaches Y
- Value restrictions
- e.g. only faculty members can teach courses
- Disjointness statements
- e.g. faculty and general staff are disjoint
- Logical relationships between objects
- e.g. every department must include at least 10
faculty
33Ontology Example
name
email
- Concept
- conceptual entity of the domain
- Property
- attribte describing a concept
- Relation
- relationship between concepts or properties
- Axiom
- coherency description between Concepts /
Properties / Relations via logical expressions
Person
Field
research field
isA hierarchy (taxonomy)
Student
Professor
attends
holds
Lecture
topic
Syllabus
holds(Professor, Lecture) gt Lecture.topic
Professor.researchField
34The 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
35The Role of Ontologies in Web Search
- 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.
36Web 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
37Web 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)
38Logic and Inference
- Logic is the discipline that studies the
principles of reasoning - Formal languages for expressing knowledge
- Well-understood formal semantics
- Declarative knowledge we describe what holds
without caring about how it can be deduced - Automated reasoners can deduce (infer)
conclusions from the given knowledge
39An Inference Example
- prof(X) ? faculty(X)
- faculty(X) ? staff(X)
- prof(michael)
- We can deduce the following conclusions
- faculty(michael)
- staff(michael)
- prof(X) ? staff(X)
40Logic versus Ontologies
- The previous example involves knowledge typically
found in ontologies - Logic can be used to uncover ontological
knowledge that is implicitly given - It can also help uncover unexpected relationships
and inconsistencies - Logic is more general than ontologies
- It can also be used by intelligent agents for
making decisions and selecting courses of action
41Tradeoff between Expressive Power and
Computational Complexity
- The more expressive a logic is, the more
computationally expensive it becomes to draw
conclusions - Drawing certain conclusions may become impossible
if non-computability barriers are encountered. - Our previous examples involved rules If
conditions, then conclusion, and only finitely
many objects - This subset of logic is tractable and is
supported by efficient reasoning tools
42Inference and Explanations
- Explanations the series of inference steps can
be retraced - They increase users confidence in Semantic Web
agents Oh yeah? button - Activities between agents create or validate
proofs
43Typical Explanation Procedure
- Facts will typically be traced to some Web
addresses - The trust of the Web address will be verifiable
by agents - Rules may be a part of a shared commerce ontology
or the policy of the online shop
44Software Agents
- Software agents work autonomously and proactively
- They evolved out of object oriented and
compontent-based programming - A personal agent on the Semantic Web will
- receive some tasks and preferences from the
person - seek information from Web sources, communicate
with other agents - compare information about user requirements and
preferences, make certain choices - give answers to the user
45Semantic Web Agent Technologies
- Metadata
- Identify and extract information from Web sources
- Ontologies
- Web searches, interpret retrieved information
- Communicate with other agents
- Logic
- Process retrieved information, draw conclusions
46Semantic Web Agent Technologies (2)
- Further technologies (orthogonal to the Semantic
Web technologies) - Agent communication languages
- Formal representation of beliefs, desires, and
intentions of agents - Creation and maintenance of user models.
47Semantic Web Outline
- Todays Web
- The Semantic Web Impact
- Semantic Web Technologies
- A Layered Approach
48A Layered Approach
- The development of the Semantic Web proceeds in
steps - Each step building a layer on top of another
- Principles
- Downward compatibility
- Upward partial understanding
49The Semantic Web Layer Tower
50Semantic Web Layers
- XML layer
- Syntactic basis
- RDF layer
- RDF basic data model for facts
- RDF Schema simple ontology language
- Ontology layer
- More expressive languages than RDF Schema
- Current Web standard OWL
51Semantic Web Layers (2)
- Logic layer
- enhance ontology languages further
- application-specific declarative knowledge
- Proof layer
- Proof generation, exchange, validation
- Trust layer
- Digital signatures
- recommendations, rating agencies .
52Web Services
53Agenda
- What are Web Services?
- Why Web Services?
- Enabling Technologies?
- What is Web Service Composition?
- Main Issues concerning the composition?
53
54Web Evolution
XML
HTML
Technology
TCP/IP
Programmability
Presentation
Connectivity
FTP, E-mail, Gopher
Innovation
Web Pages
Web Services
Browse the Web
Program the Web
54
55What are Web Services?
- Definition from W3C
- "Web Service is a software application
identified by a URI, whose interfaces and
bindings are capable of being defined, described,
and discovered by XML artifacts and which
supports direct interactions with other software
applications using XML-based messages via
internet-based protocols".
55
56What are Web Services?
- Every component that
- works in a network,
- is modular
- is self-descriptive,
- provides services independent of platform and
application, - conforms to an open set of standards and
- follows a common structure for description and
invocation.
56
57Why Web Services
- Interoperability.
- Any WS can interact with any other WS.
- Ubiquity.
- Any device which supports HTTP XML can host
access WS. - Effortless entry in this concept.
- easily understood free toolkits
- Industry Support.
- major vendors support surrounding technology.
57
58Web Services Architecture
- Components
- Service Providers
- Service Brokers
- Service Requestors
- Operations
- Publish / Unpublish
- Find
- Bind
58
5959
60Enabling technologies
- They encapsulate a set of standards that allow
the developers to implement distributed
applications. - SOAP (Simple Object Access Protocol),
- XML messaging protocol for basic service
interoperability - WSDL (Web Service Description Language)
- Common grammar for describing services
- UDDI (Universal Description Discovery and
Integration) - infrastructure required to publish and discover
services.
60
61SOAP
- Uniform way of
- passing XML-encoded data.
- performing RPCs over SMTP, FTP, TCP/IP, HTTP
- The requestor sends a msg to the service
- The service processes the msg.
- The service sends back a response.
The requestor has no knowledge of how the service
is implemented.
61
62SOAP Example
- ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas.
xmlsoap.org/soap/envelope/" SOAP-ENVencodingStyle
"http//schemas.xmlsoap.org/soap/encoding/"/gt - ltSOAP-ENVBodygt
- lteBookgt lttitlegtMy Life and Worklt/titlegt
- ltfirstauthor href"Person-1"/gt
- ltsecondauthor href"Person-2"/gt
- lt/eBookgt
- ltePerson id"Person-1"gtltnamegtHenry
Fordlt/namegt - ltaddress xsitype"mElectronic-address"gt
ltemailgtmailtohenryford_at_hotmail.comlt/emailgt
ltwebgthttp//www.henryford.comlt/webgt - lt/addressgt
- lt/ePersongt
- ltePerson id"Person-2"gt ltnamegtSamuel
Crowtherlt/namegt ltaddress xsitype"nStreet-addre
ss"gt - ltstreetgtMartin Luther King Rdlt/streetgt
- ltcitygtRaleighlt/citygt
- ltstategtNorth Carolinalt/stategt
- lt/addressgt
- lt/ePersongt
- lt/SOAP-ENVBodygt lt/SOAP-ENVEnvelopegt
62
63SOAP - RPC
- Must define an RPC protocol
- How will types be transported (in XML) and how
application represents them. - RPC parts (object id, operation name, parameters)
- ?SOAP assumes a type system based on XML-schema.
63
64SOAP Example - doGoogleSearch
- ltSOAP-ENVEnvelope xmlnsSOAP-ENV
http//schemas.xmlsoap.org/soap/envelope/
xmlnsxsi"http//www.w3.org/1999/XMLSchema-instan
ce" xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt - ltSOAP-ENVBodygt
- ltns1doGoogleSearch xmlnsns1"urnGoogleSearch"
SOAP-ENVencodingStyle"http//schemas.xmlsoap.or
g/soap/encoding/"gt - ltkey xsitype"xsdstring"gt000000000000000
00000000000000000lt/keygt - ltq xsitype"xsdstring"gtmy querylt/qgt
- ltstart xsitype"xsdint"gt0lt/startgt
- ltmaxResults xsitype"xsdint"gt10lt/maxR
esultsgt - ltfilter xsitype"xsdboolean"gttruelt/filte
rgt - ltrestrict xsitype"xsdstring"/gt
- ltsafeSearch xsitype"xsdboolean"gtfal
selt/safeSearchgt - ltlr xsitype"xsdstring"/gt
- ltie xsitype"xsdstring"gtlatin1lt/iegt
- ltoe xsitype"xsdstring"gtlatin1lt/
oegt - lt/ns1doGoogleSearchgt
- lt/SOAP-ENVBodygt
- lt/SOAP-ENVEnvelopegt
64
65SOAP Example - doGoogleSearchResult
- ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas.
xmlsoap.org/soap/envelope/" .. - ltSOAP-ENVBodygt
- ltns1doGoogleSearchResponse xmlnsns1"urnGoogle
Search" SOAP- ENVencodingStyle"http//schemas.xm
lsoap.org/soap/encoding/"gt - ltreturn xsitype"ns1GoogleSearchResult"gt
- ltdocumentFiltering xsitype"xsdboolean"gtfalselt
/documentFilteringgt - ltestimatedTotalResultsCount
xsitype"xsdint"gt3lt/estimatedTotalResultsCou
ntgt - ltdirectoryCategories xmlnsns2"http//schemas.x
mlsoap.org/soap/encoding/" xsitype"ns2Array"
ns2arrayType"ns1DirectoryCategory0"/gt - ltsearchTime xsitype"xsddouble"gt0.194871lt/sear
chTimegt - ltresultElements xmlnsns3"http//schemas.xmlsoa
p.org/soap/encoding/" xsitype"ns3Array"
ns3arrayType"ns1ResultElement3"gt - ltitem xsitype"ns1ResultElement"gt
- ltcachedSize xsitype"xsdstring"gt12klt/cachedSiz
egt - ltdirectoryCategory xsitype"ns1DirectoryCatego
ry"gtCategorylt/directoryCategorygt - ltrelatedInformationPresent xsitype"xsd
boolean"gttruelt/relatedInformationPresentgt - ltdirectoryTitle xsitype"xsdstring"/gt
- ltsummary xsitype"xsdstring"/gt
- ltURL xsitype"xsdstring"gthttp//hci.stanford.e
du/cs147/example/shrdlu/lt/URLgt - lttitle xsitype"xsdstring"gtltbgtSHRDLUlt
/bgtlt/titlegt - lt/itemgt
65
66WSDL
- IDL of Web Services
- XML format developed by IBM MS.
- Provides two types of information
- Abstract interface Application-level service
description - Protocol dependent details
66
67WSDL - Abstract interface
- Messages exchanged in an interaction.
- Components
- Vocabulary (XSD for type definition)
- Message abstract, typed data definition sent to
and from services. - Interaction
67
68Vocabulary
- ltwsdltypesgt
- ltxsdschema xmlns"http//www.w3.org/2001/XMLSc
hema" targetNamespace"urnGoogleSearch"gt - ltxsdcomplexType name"GoogleSearchResult"gt
- ltxsdallgt
- ltxsdelement name"documentFiltering"
type"xsdboolean"/gt - ltxsdelement name"searchComments"
type"xsdstring"/gt - ltxsdelement name"estimatedTotalResultsCount"
type"xsdint"/gt - ltxsdelement name"estimateIsExact"
type"xsdboolean"/gt - ltxsdelement name"resultElements"
type"typensResultElementArray"/gt - ltxsdelement name"searchQuery"
type"xsdstring"/gt - ltxsdelement name"startIndex"
type"xsdint"/gt - ltxsdelement name"endIndex" type"xsdint"/gt
- ltxsdelement name"searchTips"
type"xsdstring"/gt - ltxsdelement name"directoryCategories"
type"typensDirectoryCategoryArray"/gt - ltxsdelement name"searchTime"
type"xsddouble"/gt - lt/xsdallgt
- lt/xsdcomplexTypegt
68
69Message
- ltmessage name"doGoogleSearch"gt
- ltpart name"key" type"xsdstring"/gt
- ltpart name"q" type"xsdstring"/gt
- ltpart name"start" type"xsdint"/gt
- ltpart name"maxResults" type"xsdint"/gt
- ltpart name"filter" type"xsdboolean"/gt
- ltpart name"restrict" type"xsdstring"/gt
- ltpart name"safeSearch" type"xsdboolean"/gt
- ltpart name"lr" type"xsdstring"/gt
- ltpart name"ie" type"xsdstring"/gt
- ltpart name"oe" type"xsdstring"/gt
- lt/messagegt
- ltmessage name"doGoogleSearchResponse"gt
- ltpart name"return" type"typensGoogleSearchRes
ult"/gt - lt/messagegt
69
70Interaction
- ltbinding name"GoogleSearchBinding"
type"typensGoogleSearchPort"gt - ltsoapbinding style"rpc transport"http//schem
as.xmlsoap.org/soap/http"/gt - ltoperation name"doGetCachedPage"gt
- ltsoapoperation soapAction"urnGoogleSearchActi
on"/gt - ltinputgt
- ltsoapbody use"encoded"
- encodingStyle"http//schemas.xmlsoap.org/soap/
encoding/" namespace"urnGoogleSearch"/gt - lt/inputgt
- ltoutputgt
- ltsoapbody use"encoded" encodingStyle"htt
p//schemas.xmlsoap.org/soap/encoding/"
namespace"urnGoogleSearch"/gt - lt/outputgt
- lt/operationgt
70
71UDDI
- Global business registry
- Root under www.uddi.org
- Three types of information
- White pages
- Yellow pages
- Green pages
71
72UDDI information model
- BusinessEntity
- Info about business that publishes
- Info about service
- PublisherAssertion
- Info about relationshipbetween 2 parties
encapsulates
- BusinessService
- Descriptive info abouta service
encapsulates
- tModel
- Descriptions on specifications ofservices
- BindingTemplate
- Technical info about a serviceend point
72
73Web Service Composition
- Definition Technique of composing the
functionalities of relatively simpler services to
produce a meaningful arbitrarily complex
application.
73
74WS composition - Classification
- Proactive Composition Reactive Composition
- Proactive offline composition of available
services - When services are stable and always running
- Example ticket reservation service
- Reactive dynamically creating a composite
service. - When composite service not often used and
service processes not stable. - Example tour manager where the itinerary is not
predefined
74
75WS composition Classification (2)
- Mandatory Optional-Composite Services
- Mandatory all subcomponents must participate to
yield a result - Example service that calculates the averages of
stock values for a company. - Optional subcomponents are not obligated to
participate for a successful execution. - Example services that include a subcomponent
that is an optimizer.
75
76Important issues on WS composition
- Service Discovery
- Service Coordination and Management
- Uniform Information Exchange Infrastructure
- Fault Tolerance and Scalability
- Adaptiveness
- Reliability Transactions
- Security
- Accountability
- Testing
76
77Service Discovery
- An efficient discovery structure should be able
- find out all services implementing some
functionality (ontology) - semantic level reasoning (discover most
appropriate service). - scalable.
- Most of existing discovery infrastructures use a
central lookup server (Jini, UPnP) - Semantic Language DAML-S, a process modelling
language for computer-interpretable description
of services. - AI inspired description logic-based language,
built on top of XML RDF for well-defined
semantics and a set of language constructs and
properties.
77
78Service Discovery - DAML-S
- Enables automatic Web Service discovery.
automatic location of services with required
functionality. - Currently performed manually
- DAML-S expressed in computer interpretable
semantic markup.
78
79Service Discovery - Example of DAML-S
- ltdamlClass rdf IDCompositeProcessgt
- ltdamlintersectionOf rdfgtparseType
damlcollectiongt - ltdamlClass rdfaboutProcess/gt
- ltdamlRestriction damlminCardinality1gt
- ltdamlonProperty rdfresourcecomposedOf/gt
- lt/damlRestrictiongt
- lt/damlintersectionOfgt
- lt/damlClassgt
- ltrdfProperty rdfIDcomposedOfgt
- ltrdfs domain rdfresourceCompositeProcess/gt
- ltrdfs range rdfresourceControlConstruct/gt
- lt/rdfPropertygt
79
80Reliability Transactions
- How we can measure reliability?
- WS descriptions may lie!
- Transactions are fundamental to reliable
distributed computing. - Traditional transaction systems support ACID
semantics, use a two-phase commit approach all
participating resources are locked until entire
transaction is completed. - Only in close environments where transactions are
short-lived - Not on an open environment (flexibility in how it
is attained) - MS XLANG compensating transactions.
- Split the model into concurrent sub-transactions
that can commit independently (requires
compensation over committed sub transactions in
case of abortion).
80
81Security
- Basic security HTTP over SSL
- Authorisation control.
- Existing authorisation control frameworks not
applicable to WS (designed for some services e.g.
network access control (DIAMETER) or not well
designed to access different administrative
domains (.NET Passport)) - Proposal generic authorisation control protocol
based on SOAP/XML. Supports credential
transformation. - Need for CA in each domain. It will issue users
and services with certificate and secret key
pairs used for user authentication and request
signing. - Credentials described in an XML-based language.
Authorisation server validates the certificate,
credentials etc. If everything is successfully
validated, the authorisation server sends back a
SOAP response containing the result.
81
82Semantic Web Services
83Semantic Web Services
-
- Semantic Web Technology
-
- Web Service Technology
- allow machine supported data interpretation
- ontologies as data model
automated discovery, selection, composition, and
web-based execution of services
gt Semantic Web Services as integrated solution
for realizing Vision of Next Generation Web
Technologies of the next generation of the Web
83
84Semantic Web Services
- define exhaustive description frameworks for
describing Web Services and related aspects (Web
Service Description Ontologies) - support ontologies as underlying data model to
allow machine supported data interpretation
(Semantic Web aspect) - define semantically driven technologies for
automation of the Web Service usage process (Web
Service aspect)
84
85Semantic Web Services
- Usage Process
- Publication Make available the description of
the capability of a service - Discovery Locate different services suitable for
a given task - Selection Choose the most appropriate services
among the available ones - Composition Combine services to achieve a goal
- Mediation Solve mismatches (data, protocol,
process) among the combined - Execution Invoke services following programmatic
conventions
85
86Semantic Web Services
- Execution support
- Monitoring Control the execution process
- Compensation Provide transactional support and
undo or mitigate unwanted effects - Replacement Facilitate the substitution of
services by equivalent ones - Auditing Verify that service execution occurred
in the expected way
86
87Additional Reading (Semantic Web)
Dieter Fensel Ontologies A Silver Bullet for
Knowledge Management and Electronic Commerce,
Springer Verlag, 2001
Johan Hjelm, Creating the Semantic Web with
RDF, John Wiley, 2001
John Davies, Dieter Fensel Frank van Harmelen,
Towards the Semantic WEB Ontology Driven
Knowledge Management, John Wiley, 2002
Dieter Fensel, Wolfgang Wahlster, Henry
Lieberman, James Hendler (Eds.) Spinning the
Semantic Web Bringing the World Wide Web to Its
Full Potential, MIT Press, 2002
Michael C. Daconta, Leo J. Obrst, Kevin T. Smith
The Semantic Web A Guide to the Future of XML,
Web Services, and Knowledge Management, John
Wiley, 2003
Thomas B. Passin, "Explorer's Guide to the
Semantic Web", ISBN 1932394206, June 2004
Jeff Pollock and Ralph Hodgson, "Adaptive
Information Improving Business Through Semantic
Interoperability, Grid Computing, and Enterprise
Integration, Wiley Computer Publishing,
September 2004
M. Klein and B. Omelayenko (eds.), Knowledge
Transformation for the Semantic Web, Vol. 95,
Frontiers in Artificial Intelligence and
Applications, IOS Press, 2003
87
88Additional Reading (Web Services)
- Dipanjan Chakraborty, Technical Report
TR-CS-01-19 Dynamic Service composition
State-of-the-Art and Research Directions.
University of Maryland, Baltimore County, 2001. - Anans Rajamam, Overview of UDDI, Online, 2001.
- F.Curbera and al, Unraveling the Web Services
Web An Introduction to SOAP, WSDL, and UDDI.
IEEE Internet Computing March-April 2002,
p.86-93. - DAML Service Coalition, DAML-S Semantic Markup
for Web Services. Online at http//www.daml.org/se
rvices/daml-s/2001/10/daml-s.html, 2001. - WSDL Specification, Online at http//www.w3c.org/T
R/wsdl. - Steve Vinoski, Web Services and Dynamic
Discovery, Online at http//www.webservices.org/ar
ticle.php?sid389, 2001. - UDDI Specification, Online at http//uddi.org/.
- Sheila A. McIlaith, Tran Cao Son, Honglei Zeng,
Semantic Web Services, IEEE Intelligent Systems,
2001 - Vladimir Tosic, Bernard Pagurek, Babak
Esfandiari, Kruti Patel, On the Management of
Composition of Web Services, Carleton University,
Canada. - Tom Clements, Overview of SOAP. Online at
http//dcb.sun.com/practices/webservices/overviews
/overview_soap.jsp - Deitel,Web Services A technical Introduction,
Prentice Hall, 2002.
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