SOP Course Module 2 Slide 1

Course Module 2: Service-Oriented Programming (SOP)

SOP as a Programming Paradigmin a

Middle-Level Undergraduate Course

SOP Course Module 2 Slide 2

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 3

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 4

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 5

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 6

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 7

Programming Abstractions: Evolution

– Figure is from Introduction to Web Services by Dr. Marcello La Rosa, QUT

SOP Course Module 2 Slide 8

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 9

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 10

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 web-related standards

WSDL: Web Service Description LanguageSOAP: Simple Object Access Protocol

SOP Course Module 2 Slide 11

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 LanguageUDDI: Universal Description, Discovery and Integration

SOAP: Simple Object Access Protocol

SOP Course Module 2 Slide 1212

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

self-contained: does not need other resourcesbusiness task: simple logical step

SOP Course Module 2 Slide 13

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 14

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 15

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 16

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 17

Web Services: Commercial Frameworks

• Microsoft (Windows Communication Foundation)– http://msdn.microsoft.com/en-us/library/dd45677

9.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/s

oa/overview/index.html• Hewlett Packard – http://h71028.www7.hp.com/enterprise/w1/en/te

chnologies/soa-overview.html

SOP Course Module 2 Slide 18

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 19

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• Input: two addresses• Output: Driving directions

• 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

SOP Course Module 2 Slide 20

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/dir

ections/– Demo: http://vhost3.cs.rit.edu/Application/

SOP Course Module 2 Slide 21

SOP Basis: Service-Oriented Architecture (SOA)

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Computer

Web Service

Web Service

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ServiceRegistry

ServiceConsumer

ServiceProvider

Publish

Find

message

exchange

has defines

Service Description

UDDI Publication

UDDI Inquiry

SOAP

WSDL

UDDI Registry

Web Browser