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ISM 50 - Business Information Systems
Lectures 14
Instructor: John Musacchio
UC Santa Cruz
November 13, 2008
Class announcements
Ā For Next Class
Ā Read: MySQL Database Case
w For next Thursday
Ā Assignment 4
w Database tutorials: Ā Wed. 11/12/08, 9:30-11:00am, Jack Baskin 109; Ā Fri. 11/14/08, 2:00-3:30pm, Jack Baskin 109.
Student talks Tuesday 11/18:
- Trevor Wood (mySQL)
- David Kuepfer (Amazon)
Student Presentations
Katherine Beeskau (Business paper)
Alba Beltran (Business paper)
Implementation
Computation of key statistics
Compute Mean and Variance
Module A Implementation 1:
Module B
Ā Should he use it?
Ā NO!!!! Why??
Ā Either A should compute āSUMā himself, or sit down with B and redesign the interface
āI need to get the sum, Iāll just take it from Bā
Encapsulation
Ā The designer of B might take measures to hide āSUMā from A so that A is not able to violate the agreed interface.
Ā Example: B does not declare āSUMā as a global
variable.
Ā Making a modules implementation details inaccessible to other modules is called encapsulation.
Interfaces
Computation
N numbers of Float type
2 Numbers of float type that signify:
Compute Mean and Variance
PARAMETERS
Module B
Module A p of key statistics Mean, Variance INTERFACE RETURNS
Ā This simple interface example allows for only one action of module B. Ā Action is āCompute mean and variance.ā
Ā Other examples are possible.
Possible software interface
action- action-
i 3
Menu of actions
action- ...
Action 1: Compute mean
Action 2: Compute variance
Action 3: Compute mode
Etc..
Example:
Protocol
In addition to atomic actions, an interface may define protocols
Ā Protocol == finitesequence of actions required
to achieve a higher level functiong
Ā One action can be shared by multiple protocols
Ā Multiple modules may participate in a protocol
Protocol Example
HHC Server
HHC
Hello: Iām the gate 32 server
Hello: Iām the HHC of Airplane#
These were the unruly HHC Server passengers on last flight
Tell me about the passengers of my next flight
(Might be passed As an array of a compound data type āpassenger,ā which in turn is composed of standard types like integer, and string)
Return Passenger Data
āPassengers notedā
p g g
Another Interface Example: Automatic teller machine (ATM)
What is the interface between this machine and the customer?
Steps
Define available actions
Define, for each higher level function, a protocol
ĀĀ Single action or a finite sequence of actionsSingle action or a finite sequence of actions
Interface building blocks
Message on screen or printed
Ā Menu of actions or returns from an action Ā Touch selection of action
Keypad
ĀĀ Input parameters to an actionInput parameters to an action
Card reader
Ā Authentication, input parameters
Money output slot
Ā Returns money
Example 1
Bob (^) Alice
Bob sends a letter to Alice
US Postal Service UK Royal Mail
ABC Airlines
Envelope
Shipping Container
Shipping Container
Envelope
Layer above is a client of the layer below
Each layer provides services
Interaction of layers
Layer below as as a server to the layer above
ā¦.by utilizing the services of the layer below and adding capability
Each layer provides services to the layer aboveā¦.
Three types of software
Application
ā¢Components and frameworks:
ā¢Infrastructure: Basic services (communication, storage, concurrency, presentation, etc.)
What is in common among applications
Data and information
Application Deals with information
Infrastructure Deals with data
Assumes structure and interpretation
Ignores structure and interpretation
Architecture
HHC HHC Server
Wireless Link
Airline Dataserver
HEADQUARTERS
HHC Server
Airline Intranet
System requirements Requirements
Available components
Two ways to design a system
Decomposition from system requirements
Assembly from available components Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Component : A subsystem purchased āas isā from an outside vendor
Components
(Alternative ā building your own subsystem)
A component implementation is encapsulated (although often configurable)
your own subsystem)
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
HHC Architecture
HHC Application Coordination User Interface With HHC Server
The Palm OS we are buying āoff the shelfā and
integrating into our architecture.
The Palm OS is a component.
Palm OS
Networking Infrastructure
Data Management
Other Examples of components
Computer
Disk drive
Network
N t k t
Why is a component
implementation
Network router encapsulated?
Operating system
Integrated circuit
Database management system
encapsulated?
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Interoperability
Ā Components are interoperable when they interact
properly to achieve some desired functionality
Ā Increasingly component interoperability cannot
be dependent on end-user integration
Ā PC and peripherals Ā Enterprise, inter-enterprise, consumer applications Ā Role for standardization
Outsourcing: A subsystem design is contracted to an outside vendor
Outsourcing
Responsibility is delegated
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
HHC Architecture
HHC Application (^) With HHC ServerCoordination User Interface
Ā Suppose we choose to pay another firm to develop the user interface. Ā This is called Outsourcing. Ā Why would we do this?
Palm OS
Networking Infrastructure
Data Management
Four possibilities
Application
Product Service
Microsoft Office Hotmail
Application
Infrastructure
Personal computer Internet DNS
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Application Service Provider
Ā Two types
Ā Bundled
Ā An infrastructure provider bundles applications with their infrastructure Ā EE xample: AOL, telephony service providersl l h d
Ā Unbundled
Ā A provider of an application service without providing an infrastructure service Ā Examples?
Examples of unbundled ASP
model
Ā Yahoo: Web-based calendar
Ā Hotmail: Web-based email
ĀĀ Schwab: Web-based stock tradingSchwab: Web based stock trading
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Unbundled ASP model
Advantageous to user
Ā Proven way to reduce installation, integration,
and maintenance costs
Ā Contractual obligation for availability andg y
quality
Ā Location independence
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Unbundled ASP model (conāt)
Advantages to supplier
Ā Ongoing revenue stream supporting upgrade and
maintenance
Ā Usage-based revenue better aligned with userāsg g
value proposition
Ā Opportunity for price discrimination,
advertising revenue, etc.
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Some pricing alternatives
Price discrimination?
Usage dependent?
Terms and conditions
Ā fixed, leasing, per-use, subscription ĀĀ warrantee service level agreementswarrantee, service level agreements
Bundles
Ā maintenance, support, releases, provisioning and operations
Who pays?
Ā sometimes not the end user
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Infrastructure acquisition
Build and operate
Infrastructure Build but do not operate
Do not build but operate
Neither
Outsourced operations
System Trend integrator
Service provider
Slide adapted from slides for Understanding Networked Applications By David G Messerschmitt. Copyright 2000. See copyright notice
Application acquisition
Buy as Application (^) product Develop internally
Contract development
Software supplier
Outsource Trend developer
Product w/ customization
Supplier, consultants
