Æliens

1

• themes and variations -- object speak
• abstraction -- paradigms of programming
• software development -- the OO life-cycle
• object technology -- trends

Additional keywords and phrases: object, data abstraction, analysis, design, implementation, distribution

• abstraction -- the object metaphor
• modeling -- understanding structure and behavior
• software architecture -- mastering complexity
• frameworks -- patterns for problem solving
• components -- scalable software

Object terminology

object speak

• objects -- packet containing data and procedures
• methods -- deliver service
• message -- request to execute a method
• class -- template for creating objects
• instance -- an object that belongs to a class
• encapsulation -- information hiding supported by objects
• inheritance -- mechanism allowing the reuse of class specifications
• class hierarchy -- tree structure representing inheritance relations
• polymorphism -- to hide different implementations behind a common interface

• information hiding -- state, autonomous behavior
• data abstraction -- emphasis on what rather than how
• dynamic binding -- binding at runtime, polymorphism
• inheritance -- incremental changes (specialization), reusability

OO = encapsulation + inheritance

benefits of OOP

• modularity -- autonomous entities, cooperation through exchanges of messages
• deferred commitment -- the internal workings of an object can be redefined without changing other parts of the system
• reusability -- refining classes through inheritance
• naturalness -- object-oriented analysis / design, modeling

the object model

• computation is sending messages between objects

message

• object method arguments

encapsulation

• objects encapsulate data and procedures

protocol

• the collection of messages an object supports

Computing devices

• mathematical model -- Turing machine
• universal machine -- machines as programs
• computability \& complexity -- time/space bounded

Object-oriented programming does not enlarge the class of computable problems, nor does it reduce the computational complexity of the problems we can handle.

Encapsulation

• abstract data types

Object-oriented modeling

• data oriented

• to specify behavior

  what rather than how

client/server model

• makes request to perform a service

• provides service upon request

Contracts

• a set of services

• improving contracts

Conformance -- behavioral refinement

Object-oriented modeling

• prototyping, specification, refinement, interactions

  while ( programming == art )  {
  
  	incr( pleasure );
  	decr( bugs );
  	incr( portability );
  	incr( maintainability );
  	incr( quality );
  	incr( salary );
  
  } // live happily ever after
  

Support for data abstraction

• Abstract Data Types -- encapsulation

Encapsulation

• initialization
• protection
• coercions

Support for OOP

• Polymorphism -- inheritance

Inheritance

• dynamic binding
• protection
• multiple inheritance

• Analysis -- Conceptual Model, System Requirements
• Design -- System Design, Detailed Design
• Implementation -- Coding, Testing

With an increase in the number of software products not satisfying user needs, prototyping has become quite popular!

Requirements -- user needs are constantly evolving

• Reliability -- incremental development, reuse, synthesis
• Adaptability -- evolutionary prototyping
• Maintainability -- incremental development, synthesis
• Performance -- incremental development, reuse

Software development models

• rapid throwaway prototyping -- quick and dirty
• incremental development -- slowly evolving
• evolutionary prototyping -- evolving requirements
• reusable software -- reduces cost and time
• automated software synthesis -- one level of abstraction higher

• analysis = extracting the needs

The problem domain -- complex reality
Communication -- with domain experts
Continual change -- user requirements
Reuse -- of analysis results

Abstraction -- procedural / data
Encapsulation -- information hiding
Inheritance -- expression of commonality
Message passing -- consistent interface
Organization -- object / attributes
Scale -- components, frameworks
Behavior -- actors, servers, agents

• Functional Decomposition = Functions + Interfaces
• Data Flow Approach = Data Flow + Bubbles
• Information Modeling = Entities + Attributes + Relationships
• Object-Oriented = Objects + Inheritance + Message passing

• correctness, robustness, extendibility, reusability, compatibility

  Requirements change --  41.8% 
  Data format change --  17.4% 
  Emergency fixes --  12.4% 
  Routine debugging --  9% 
  Hardware changes --  6.2%
  Documentation --  5.5% 
  Efficiency improvements -- 4%
  

IDA

An Interior Design Assistant (IDA) is a tool to support an interior design architect. When designing the interior of a house or building, the architect proceeds from the spatial layout and a list of furniture items. IDA must allow for placing furniture in a room. It will check for constraints. For example placing a chair upon a table will be prohibited. For each design, IDA must be able to give information with respect to pricing and the time it takes to have the furniture items delivered. In addition to the design facilities, IDA must also offer a showroom mode, in which the various designs can be inspected and compared with respect to price and delivery time.

MASS

An Agenda Support System assists the user in maintaining a record of important events, dates and appointments. It moreover offers the user various ways of inspecting his or her agenda, by giving an overview of important dates, an indication of important dates on a calendar, and (more advanced) timely notification.

A Multi-user Agenda Support System extends a simple Agenda Support System by providing facilities for scheduling a meeting, taking into account various constraints imposed by the agendas of the participants, as for example a special event for which a participant already has an entry in his or her agenda. A minimal Multi-user Agenda Support System must provide facilities for registering important dates for an arbitrary number of users. It must, moreover, be able to give an overview of important dates for any individual user, and it must be possible to schedule a meeting between an arbitrary subset of users that satisfies the time-constraints for each individual in that particular group.

This minimal specification may be extended with input facilities, gadgets for presenting overviews and the possibility of adding additional constraints. Nevertheless, as a piece of advice, when developing a Multi-user Agenda Support System, follow the KISS principle: Keep It Simple ...

TeX

• [A] -- algorithm awry
• [B] -- blunder
• [C] -- structure debacle
• [F] -- forgotten function
• [L] -- language liability
• [M] -- mismatch between modules
• [R] -- reinforcement of robustness
• [S] -- surprises
• [T] -- a trivial typo

• rapid prototyping

• correctness

• the benefits of efficiency

• security

• development of knowledge-based systems

• vertical framework development -- finance, medical care, insurance
• separation of 'logic' from 'control' -- business rules
• distributed object technology -- heterogeneous systems
• visualisation -- structure and processes
• knowledge intensive applications -- declarative
• heterogeneous systems -- fragmented applications

1

• terminology -- all phrases
• object computation -- message passing
• contracts -- for constructing and validating software

2

• styles of programming -- as a family of conventions
• data abstraction -- and its possible realizations
• polymorphism -- and the features of inheritance

3

• software development models -- in particular the role of prototyping
• software quality -- in relation to reuse and maintenance
• programming languages -- the choice of a vehicle

4

• modeling -- patterns, UML
• components -- CORBA, (D)COM, Java
• heterogeneous systems -- separating logic and control