EPL603 Advanced Software Engineering

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EPL603Advanced Software Engineering

• George A. Papadopoulos
• Department of Computer Science
• george_at_cs.ucy.ac.cy
• http//www.cs.ucy.ac.cy/george
• Course URL
• http//www.cs.ucy.ac.cy/courses/EPL603

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Todays Software Development

• Development of large complex systems
• Software systems must fulfill the requirements of
  stakeholders (clients, end-users, developers,)
• Number of persons involved in the development gt
  1
• Software systems are expected to live long and be
  used by many people

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What are the Problems?

• Increased quality demands on software products
• High cost and time pressure
• Shorter time to market
• Coordination problems within the projects
• Scarce resources

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The Software Crisis/Solution

• 1968 NATO conference in Garmisch-Partenkirchen
• Software crisis (to characterize the situation)
• Software engineering (idea for a solution)

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Whats Software Crisis?

• Unacceptably low quality of software
• Delayed deadlines Average 1 year

• Over cost limits Average 2X estimate
• E.g. Air Force Command and Control system
• Initial estimate
• 1.5million
• Winners bid
• 0.4 million
• Actual cost
• 3.7 million

• After deliver?
• E.g. U.S Army study of
• Federal projects
• Delivered, but not used 47
• Paid for, but not delivered 29
• Abandoned or reworked 19
• Used after changes 3
• Used as delivered
• 2

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Example Practical Disasters

• European Space Agency Ariane 5
• Track control system failure results in self
  destruction
• Denver Airport
• Late delivery of software for the baggage system
  delays the opening of the airport by 16 months
• US study (1995) 81 billion US spend per year
  for failing software development projects

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Why is Software so Hard?

• Software is Parnas, 1985
• Buggy
• Unreliable
• Forever changing
• Unwarrantable

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Definition Software Engineering
The application of a systematic, disciplined,
quantifiable approach to the development,
operation, and maintenance of software IEEE-93
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Three Ps
People
Processes
Products
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People, Processes, Products

• People
• education
• skills
• communication
• style
• .....

• Products
• requirements
• design
• source code
• executable
• user documentation
• test cases
• test results
• change request
• ....

• Processes
• planning
• coordination
• management
• measuring
• analyzing
• designing
• coding
• .....

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Scope Software Engineering

• various disciplines
• Mathematics,
• Computer science,
• Economics,
• Management,
• Psychology
• etc.

• extremely broad
• the software life cycle
• team or organization
• economic aspect
• legal aspect,
• etc.

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Why still Software Engineering?

• Has the software crisis vanished? No!
• Software projects still run over time and out of
  budget
• no break through in quality !!!still art
  instead of engineering discipline

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What is a Distributed System?

• A collection of autonomous hosts that that are
  connected through a computer network.
• Each host executes components and operates a
  distribution middleware
• Middleware enables the components to coordinate
  their activities
• Users perceive the system as a single,
  integrated computing facility.

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What is a Distributed System?
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Middleware Examples

• Transaction-oriented
• IBM CICS
• BEA Tuxedo
• IBM Encina
• Microsoft Transaction Server
• Message-oriented
• Microsoft Message Queue
• NCR TopEnd
• Sun Tooltalk

• Procedural
• Sun ONC
• Linux RPCs
• OSF DCE
• Object-oriented
• OMG CORBA
• Sun Java/RMI
• Microsoft COM
• Sun Enterprise Java Beans

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Centralized vs. Distributed System

• One component with non-autonomous parts
• Component shared by users all the time
• All resources accessible
• Software runs in a single process
• Single Point of control
• Single Point of failure

• Multiple autonomous components
• Components are not shared by all users
• Resources may not be accessible
• Software runs in concurrent processes on
  different processors
• Multiple Points of control/failure

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Real World Example Hongkong
Telecom

• Video-on-demand provide subscribers with
  facilities to download videos from HK TK servers
  to low-cost Web-TVs.
• currently 90,000 users.
• Built using distributed object-technology.

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Requirements

• Hardware
• Clients Web-TV
• Servers RISC processor
• Operating System Heterogeneity
• Clients Java OS
• Servers UNIX
• Programming Language Heterogeneity
• Clients Java
• Servers C

• Communication across Network
• How to transmit complex data structures across
  the Internet?
• Scale
• Scaling from initially several hundred to
  currently 90,000 users
• Security
• Secure Payment
• Authentication

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Why Distributed Object Technology?

• Distributed
• Video clients need to download/show video on
  customers Web-TV
• Multiple servers needs to be operated by Hongkong
  Telecom
• Object Technology
• Video clients are written in Java
• Web-TV has Java Virtual Machine
• portability to e.g. Sony Playstation,
  Sega-Console...
• Video servers are written in C
• high performance

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Another ExampleIT Infrastructure of UBS
Customer Information Services
Authorisation Services
Trading Workstation
Product Database Services
Marketing Services
Host Services
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Requirements

• Time to market
• Development of new applications with recent
  technology
• Integration of new applications increasingly
  difficult
• Scalability
• Management of 30,000,000 accounts
• Management of 10,000,000 customers
• Use by 2,000 concurrent users
• Reliability

• Hardware Heterogeneity
• Unisys Mainframes
• IBM Mainframes
• SPARC Servers
• PC Workstations
• Operating System Heterogeneity
• MVS
• UNIX
• Win-NT
• Programming Language Heterogeneity
• Cobol
• C/C
• Visual Basic

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Why Distributed Object Technology?

• Uniform view of all banking services
• Appropriate level of abstraction
• Preserving investment by wrapping legacy
  applications
• Exploiting advantages of object technology for
  new development
• Resolving
• distribution
• heterogeneity

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Boeing 777 Configuration Mgmnt.
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Requirements

• Scale
• 3,000,000 parts per aircraft
• Configuration of every aircraft is different
• CAA regulations demand that records are kept for
  every single part of aircraft
• Aircraft evolve during maintenance
• Boeing produce 500 aircraft per year
• Configuration database grows by 1.5 billion parts
  each year
• Projected life of each aircraft 30 years
• 45,000 engineers need on-line access to
  engineering data

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Requirements

• COTS Integration
• Existing IT infrastructure was no longer
  appropriate
• Boeing could not afford to build required IT
  infrastructure from scratch
• Components were purchased from several different
  specialized vendors
• relational database technology
• enterprise resource planning
• computer aided project planning
• Components needed to be integrated

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Requirements

• Heterogeneity
• 20 Sequent database machines as servers for the
  engineering data
• 200 UNIX application servers
• NT and UNIX workstations for engineers

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Why Distributed Object Technology

• Object wrapping of COTS
• Resolution of distribution at high level of
  abstraction
• Resolution of heterogeneity
• Scalability

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Distributed System Requirements

• Integration of new, legacy and components
  off-the-shelf
• Legacy components might not need to be
  re-engineered
• COTS cannot be modified
• Heterogeneity of
• hardware platforms
• operating systems
• networks
• programming languages
• Construction of distributed systems

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Course Content - 1

• Introduction to Components and Component-Based
  Software Engineering
• Fundamental Concepts
• Components vs Objects
• Patterns
• Software Architectures
• Coordination Models and Language
• Software Composition

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Course Content -2

• Middleware Platforms and Component Based Systems
  Development
• COM/DCOM/ActiveX
• CORBA
• Jini
• Development of Component Based Systems
• Architectures and Component Frameworks
• Development of Components in Distribute Systems
• Related Programming Languages
• Configuration Management