Course Module 2: Service-Oriented Programming (SOP) SOP as a Programming Paradigm in a Middle-Level Undergraduate Course

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.

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

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: 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

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

Programming Abstractions: Evolution Figure is from Introduction to Web Services by Dr. Marcello La Rosa, QUT

Service-Oriented Programming (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

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

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 Language SOAP: Simple Object Access Protocol

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

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 resources business task: simple logical step

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

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: 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 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

Web Services: Commercial Frameworks Microsoft (Windows Communication Foundation) http://msdn.microsoft.com/en-us/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/technologies/soa-overview.html

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: Designing the Application Traditional design approach Develop a gas station service Input: address Output: gas stations nearby Develop a weather service 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

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.) For location service: use Google Directions API https://developers.google.com/maps/documentation/directions/

SOP Basis: Service-Oriented Architecture (SOA) Web Service Service Registry Consumer Provider Publish Find message exchange has defines Service Description UDDI Publication UDDI Inquiry SOAP WSDL UDDI Registry Web Browser