Transcript SOP Module 2 Slides - Computer Networks Lab

Course Module 2:
Service-Oriented Programming
(SOP)
SOP as a Programming Paradigm
in a
Middle-Level Undergraduate Course
SOP Course Module 2
Slide 1
Acknowledgments
• This material is based upon work supported
by the National Science Foundation under
Awards No. DUE-1140567, DUE-1141112, and
DUE-1141200. Any opinions, findings, and
conclusions or recommendations expressed in
this material are those of the authors and do
not necessarily reflect the views of the
National Science Foundation.
SOP Course Module 2
Slide 2
Module Learning Outcomes
• Students will be able to:
– Describe the role and importance of service-oriented
programming in current application development
– Explain the basic concepts of web services and
service-oriented architecture
– Explain the standards underlying service-oriented
architecture and web services
– Build and use web services using C# or Java
– Explain how software reuse and quality are improved
by the use of web services’ composition
SOP Course Module 2
Slide 3
Common Programming Paradigms
• Imperative paradigm
– Based on von Neumann architecture where computation combines
logic (what is to be done) and control flow (how it is to be done)
• Functional paradigm
– All computations are done by defining and applying (calling)
mathematical functions
• Logic paradigm
– Computation is a systematic attempt to satisfy a goal based on
provided facts and inference rules
• Object-oriented paradigm
– Objects represent state and behavior, and computation is
accomplished by messages sent among objects
– Objects created from classes and inheritance provide software reuse
SOP Course Module 2
Slide 4
SOP: Another Programming Paradigm
• SOP is a new programming paradigm
• Uses “services” as the unit of work to design
and develop integrated business applications
and mission critical software programs
• Inherently designed to reuse existing services
• Naturally supports software reuse, which in
turn helps to improve software quality
SOP Course Module 2
Slide 5
Object- and Service-Orientation
• Steps in solving a complex problem
– Abstraction
• Decomposes problem into sub-problems
• Solves each sub-problem and compose the overall solution
– Object-orientation
• Describes an abstraction using objects
• Objects help to model problem and develop the solution
– Service-orientation
• Describes an abstraction using services
• Services help to model problem and develop the solution
• Developed service can be used to develop new services
SOP Course Module 2
Slide 6
Programming Abstractions: Evolution
– Figure is from Introduction to Web Services by Dr.
Marcello La Rosa, QUT
SOP Course Module 2
Slide 7
Service-Oriented Programming (SOP)
• SOP
– A programming paradigm that uses “services” as the
building block to develop applications
• Approach
– Develop services
– Make use of services by invoking (calling) others
– Combine services to make additional services
• Main ideas
– Make use of web services
– Should be easy to make use of web services
SOP Course Module 2
Slide 8
What is a Web Service?
• A service (high-level description)
– Similar to a method
– A program calls a method and gets some results back
• A web service (high-level description)
– A service that can be invoked by a program over the
web (http)
• A web service is different from a web application
– A web application is for use by humans
• Such as http://www.weather.com
– A web service is for use by programs
• Such as Twitter APIs https://dev.twitter.com/docs/api/1
SOP Course Module 2
Slide 9
Web Service: Definition
• From W3C (World Wide Web Consortium)
– It is a software system designed to support interoperable
machine-to-machine interaction over a network
– Its interface is described in a machine-processable format
(specifically WSDL)
– Other systems interact with the Web service as specified
by its description using SOAP messages, typically over
HTTP with an XML serialization along with other webrelated standards
WSDL: Web Service Description Language
SOAP: Simple Object Access Protocol
SOP Course Module 2
Slide 10
Web Services: Features and Standards
• Global accessibility via the web
– Leverages web’s powerful communication paradigm
– Accessible via HTTP (across firewalls)
• Standardization, XML-based
–
–
–
–
WSDL: used for service description (www.w3.org/TR/wsdl)
UDDI: for service publishing and discovery (uddi.xml.org/)
SOAP: for service invocation (www.w3.org/TR/SOAP/)
Others
WSDL: Web Service Description Language
UDDI: Universal Description, Discovery and Integration
SOAP: Simple Object Access Protocol
SOP Course Module 2
Slide 11
Examples of Web Services
• A self-contained business task
– A money withdrawal or funds deposit service for a bank
• A full-fledged business process with multiple tasks
– Automated purchasing of office supplies with approvals at
different levels
• An application
– A complete life insurance application
• A service-enabled resource
– Access to a remote database containing patient medical
records
SOP Course Module 2
self-contained: does not need other resources
business task: simple logical step 12
Slide 12
What Web Services Bring to SOP
• OOP typically constrained to homogeneity
– Same data types, programming languages,
development platform, operating systems
• Web services handle heterogeneity
– Extensive use of XML as it has become ubiquitous
– Deal with the accessibility by providing access to
functionalities available on the web (standard
networking and http)
• SOP
– Builds on web services to support software reuse
SOP Course Module 2
Slide 13
Accessing Functionality
• Traditional software development
– Download functionality in a code library and link new
code to use it
• SOP software development
– Access to functionalities already on the web
• Use existing networking infrastructure
• HTTP has become ubiquitous
• OOP software development
– Can also use functionality but needs some access
mechanisms to identify functionality
SOP Course Module 2
Slide 14
SOP: A New Problem Solving Paradigm
• Traditional software development
– Develop a new app from scratch
• SOP
– Develop a new app not from scratch but by using
existing services
• Decompose problem into sub-problems
• For each sub-problem, select existing or develop
appropriate services
• Combine these services together to create new app
SOP Course Module 2
Slide 15
SOP At Present
• Major companies support web services
– Microsoft, IBM, HP, Oracle, BEA, SAP, and others
– Deliver their functionalities as web services
• Many web services available published online
– Over 11,101 web services and 7,364 mashups (SOP apps)
• http://www.programmableWeb.com
– Other search engines for web services
• http://www.webservicelist.com
• http://www.biocatalogue.org (curated catalog for life sciences)
• Web transformation
– From an information repository to a service repository
SOP Course Module 2
Slide 16
Web Services: Commercial
Frameworks
• Microsoft (Windows Communication Foundation)
– http://msdn.microsoft.com/enus/library/dd456779.aspx
• IBM (“simply good design”)
– http://www-01.ibm.com/software/solutions/soa/
• Oracle (“agile and reusable connectivity”)
– http://www.oracle.com/us/products/middleware/soa
/overview/index.html
• Hewlett Packard
– http://h71028.www7.hp.com/enterprise/w1/en/tech
nologies/soa-overview.html
SOP Course Module 2
Slide 17
SOP: An Example Application
• Develop a web-based query application to
allow users view gas stations, local weather
and driving information at a given location
• Input
– address
• Output
– List of gas stations
– Local weather
– Driving directions
SOP Course Module 2
Slide 18
SOP: Designing the Application
• Traditional design
approach
– Develop a gas station
service
• Input: address
• Output: gas stations nearby
– Develop a weather service
• Input: address
• Output: local weather
– Develop a route service
• Not trivial to develop any
of these services
• SOP approach
– First see if existing web
services can handle one or
more of the above
– Use those functionalities
via existing web services
– Build the rest
• Input: two addresses
• Output: Driving directions
SOP Course Module 2
Slide 19
The Three APIs
• For hotel service: use Expedia APIs
– http://developer.ean.com/docs/hotels/
– Demo: http://vhost3.cs.rit.edu/Application/
• For weather service: use Weather underground API
– http://www.wunderground.com/weather/api/d/docs
– (weather, humidity, temperature, wind speed, etc.)
– Demo: http://vhost3.cs.rit.edu/Application/
• For location service: use Google Directions API
– https://developers.google.com/maps/documentation/dire
ctions/
– Demo: http://vhost3.cs.rit.edu/Application/
SOP Course Module 2
Slide 20
SOP Basis: Service-Oriented
Architecture (SOA)
Service
Registry
Web Browser
0.0000
UDDI Registry
Publish
UDDI Publication
Find
UDDI Inquiry
Service
Consumer
message
Web Service
0.0000
defines
has
exchange
Service
Provider
0.0000
Web Service
SOP Course Module 2
SOAP
Service Description
WSDL
Slide 21