Lecture 2

• Lecture 2
  • Video
  • Slides
  • Summary from last class
  • Computing as a utility
  • Publishing and all for services
  • Services on the cloud
  • What is a service
  • SOA - service Oriented Architecture
  • IaaS
  • PaaS
  • SaaS

Video

link

Slides

link

Summary from last class

Computing as a utility

• paytech has service - payroll processing
• takes some input and gives output
• companies upload their employees data and paytech service processes and sends report regarding benefits and all
• the payroll process are different for each company
• the steps are similar, but actual details are different
• If I make a generic service interface, every company can use same service provided it is encapsulated as well

• modules can be changed later but interface remains same

Publishing and all for services

• a shop who advertises more has more customers than one who does not
• Yellow pages pe company apni contact info and description deti
• aisi hi kuch, I require for s/w also
• Service LAyer
  • should have functionality of lookup and discovery, service description
  • could be a manual effort or program should also be able to search and all
  • XML/JSON format me specify karde ki service ko contact kaise kare, what will be input, what will be output

• I do not have to know where service is located.
• No physical binding is required = Reduces Coupling - Deployment Dependencies
  • I do not have to connect sockets and all
• Due to service layer, infrastructure is not needed to be limited to a particular location, Paytech will not worry about it
• So, paytech will move its payroll service to some data center/cloud

Services on the cloud

• core buisness of paytech is now separated from infrastructure part
• it could just focus on payroll service
• Consumer is consumer of applicaiton provider
• Cloud provider is one which provides infrastructure to application provider
• there could be several service providers in cloud
• and client can use one according to their comfort
• So, cloud is all about services now a days
  • service could be platform, infrastructure, database, software, etc

What is a service

• product is present in front of us, but service is not
• doctors offer services, medicine is product
• provider is providing some features

• in product, u know what outcome it is
• process me, u should quantify somehow

• I need to have some expectations from service and they should be verified

• so we have some contracts, terms defined that should be met from provider and consumer side

SOA - service Oriented Architecture

• there is a diff b/w using fn in a program, and serviceo ver web

• What is the difference between calling a function in a program, calling a service over web
• service oriented arch is tied closely to object-oriented architecture
  • If I send some data to network, I want it to remember it, I do not want to send again and again

• object oriented me, state nahi pass karni

• either we know already interface details, or we lookup

• now, we do not need to know the interface either, we pass parameters
• XML form me pass karde
• no language specific bindings is required
• I might have service in C, and calling it in python

• state, execution, interface, location all are hidden

IaaS

• offering the processing power, network, storage
• consumer has control on os, storage, deployed apps
• but which machine, vm etc is not under control

PaaS

• libraries, tools are provided by cloud provider, using those u write ur own apps

SaaS

• everyth is under control of cloud provider
• eg, Gmail, google docs, CRM from Salesforce.com
• I just use these