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4 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Semantic Web
Services



Notes

Slide
2
: Web Evolution



Web 1.0


Information Web



Read
-
only Web
-

Brochureware



Static content, infrequently updated, little interactions between sites



Slow, page refresh when new info was added, session state not handled well



Web search


hopeless



Software sold as application, not service



Web 2.0


Social Web



Read
-
Write Web



Deliver continually
-
updated services



Harness social side


let users to create data and filter after their behaviour



Let users create apps using your data


Web Services



Web 3.0


Intelligent Web



Computer
-
processable meaning



Machines talking to machines (Tim Berners
-
Lee vision)



Challenges: increased complexity



Web 4.0


3D Web




Ambient findability, tagging



RFID readers and writers integrated in mobile devices

Slide
4
:
Web Services

(1)

W3C (2004) defines a Web Service as “…a software system designed to support

interoperable
machine
-
to
-
machine interaction over a network. It has an interface

described in a machine
-
processable format (specifically WSDL). Other sys
tems

interact with the Web service in a manner
prescribed by its description using SOAP

messages, typically conveyed using HTTP with an XML
serialization in conjunction

with other
Web
-
related standards.”

Web Service


application of Service Oriented
Architecture

Slide
5
:
Web Services

(
2
)

The current Web services technology basically provides

a syntactical soluti
on and still lacks the
semantic
part. A Web service is

described in WSDL, outlining
what input the ser
vice expects and
what output it
returns.

To exploit their po
tentials (beyond the enterprise
application int
egration),
Web services must be
able to orchestrate themsel
ves into more complex services.
Thus, we nee
d
methods to combine individual
Web services into a distributed, higher
-
level service.

Slide
6
:
Semantic
Web Services

(1)

Definition: server end of a client
-
server system for machine
-
to
-
machine interaction via WWW.

It uses markup to make data machine
-
understandable
-
> independent interaction among agents

Slide 7: SWS (2)

Semantic Web Servic
es: Intelligent, high
-
level

services like information brokers, search agents,

information filters, intelligent information integration,

and knowledge management, are what the
users want

from the Semantic Web. They are possible only if a

number of
ontologies populate the
Web, enabling

semantic interoperation between the agents and the

applications on the Semantic
Web, i.e. semantic

mappings between terms within the data, which

requires content analysis.

SWS
support

the automatic discovery, compositi
on, invocation and interoperation of services
.

Slide 8: WS description layers

Web services description has three layers:



the service invocatio
n description (in a WSDL file)



the publication and discovery desc
ription (in the UDDI registry)



t
he composite web
services description (in the stat
ic case e.g. in a BPEL4WS file)

UDDI



Universal Description Discovery and Integration

WSDL



Web Service Definition Language

Slide 10: Building a SWS (2)

The key to semantic description is
the service invocation descriptio
n
, because the other descriptions
build on the information available in
the individual service descriptions
. The individual service
description has to support two major aspects:
the description of the functionality of the web
service

and
the description of

the data the web service operates on. Adding semantics to data
description can build on ontology descriptions of knowledge representation techniques. The data
semantics cannot simply be extracted from WSDL descriptions, because e.g. a string data type can

represent semantically different information. The semantic data descriptions contain concepts of a
given domain ontology.

The major elements needed for the semantic description of web service
s, identified by the OWL
-
S
and the WSMO approach, are

the follow
ing:



Inputs: the input data of the service defined by a given domain ontology



Pre
-
conditions: conditions on the inputs of the service defined by a given domain ontology



Outputs: the output data of the service defined by a given domain ontology



Post
-
conditions: conditions on the outputs of the service defined by a given domain
ontology



Textual description: human readable description of the service

Slide 14: SWS Frameworks



WSMF

-

Web Service Modelling Framework



OWL
-

S



QuASAR



Quality Assurance of Semantic Annotations For Services




WSMO
-

Web Service Modeling Ontology



SSWAP
-

Simple Semantic Web Architecture and Protocol

Slide 15: OWL

S

(1)

Development of OWL
-
S aims to enable the following tasks:

Automatic Web service discove
ry: with the development of the Semantic Web, many Web Services
will be available on the Web, performing the most various tasks. OWL
-
S will help software agents to
discover the Web Service that would fulfil a specific need within some quality constraints,
without
the need for human intervention.

Automatic Web service invocation: generally, it is necessary to write a specific program to invoke a
Web Service, using its WSDL description. OWL
-
S will open the possibility for a software agent to
automatically rea
d the description of the Web Service's inputs and outputs and invoke the service.

Automatic Web service composition and interoperation: in a Web where many services are
available, it should be possible to perform a complex task, involving the coordinated i
nvocation of
various Web Services, based solely on the high
-
level description of the objective. OWL
-
S will help in
the composition and interoperation of the Services in a way that will enable the automatic execution
of these tasks.

Slide 16: OWL
-
S (2)



The
service profile is used to describe what the service does. This information is primary
meant for human reading, and includes the service name and description, limitations on
applicability and quality of service, publisher and contact information.



The proce
ss model describes how a client can interact with the service. This description
includes the sets of inputs, outputs, pre
-
conditions and results of the service execution.



The service grounding specifies the details that a client needs to interact with the
service, as
communication protocols, message formats, port numbers, etc.

Slide 18: Projects



SWSI



Semantic Web Service Initiative



SUPER



Semantics Utilized for Project Management within and between Enterprises



FUSION

-

Business process fusion based on Semantically
-
enabled Service
-
oriented Business
Applications



SHAPE



Semantically
-
enabled Heterogeneous Service Architecture and Platforms
Engineering

Slide 20: SWSI (2)


Semantic Web Technology

Automated services will improve in their capacity to assist humans in achieving their goals by
"understanding" more of the content on the Web, and thus providing more accurate filtering,
categorization, and searches of information sources. This process wil
l ultimately lead to an
extremely knowledgeable system that features various specialized reasoning services. These
services will support us in nearly all aspects of our daily life
-

making access to information as
pervasive, and necessary, as access to ele
ctricity is today.




Web Service Technology

Recent efforts around UDDI, WSDL, and SOAP try to lift the Web to a new level of service. Software
applications can be accessed and executed via the Web based on the idea of Web services. Web
services can
significantly increase the Web architecture's potential, by providing a way of
automated program communication, discovery of services, etc
.



Intelligent Web Services

Current technology around UDDI, WSDL, and SOAP provide limited support in mechanizing

service
recognition, service configuration and combination (i.e., realizing complex workflows and business
logics with Web services), service comparison and automated negotiation
.





Slide 21: Applications

An example would be supply chain relationships where an enterprise manufacturing short
-
lived
goods must frequently seek suppliers as well as buyers dynamically. Instead of employees constantly
searching for suppliers and buyers, the Web service infrastruct
ure does it automatically within the
defined constraints.

Other applications areas for this technology are Enterprise
-
Application Integration (EAI), eWork, and
Knowledge Management.