winter term 2011/12 prof. dr. dr. h. c. dieter rombach ...€¦ · basics of se – software...

Software Engineering Research Group: Processes and MeasurementFachbereich InformatikTU Kaiserslautern

Last update: 31.10.2011

Grundlagen des Software EngineeringFundamentals of Software Engineering

Winter Term 2011/12

Prof. Dr. Dr. h. c. Dieter Rombach

Chapter 2.1:

Basics of Software Engineering – Software Product

� Product Reference

Model�SW Application Eng

�SW System Eng

�SW Unit Eng

�Virtual vs. Real Product

�Reverse-/Re-/Forward Eng.

� SE Principles�Dev. Model

�Principles

�G x P Matrix

� Description

Techniques�Views of Description

�Basic Techniques

© Prof. Dr. Dr. h. c. Dieter Rombach, Fundamentals of Software Engineering, Winter Term 2011/12 1

Basics of SE –Software Product Goals

� The goals of this chapter are to

– understand the basic product-related principles for engineering based software development, including

→ Software product reference model

→ Software product related software engineering principles

→ Basics of description techniques

→ Basics of modularization techniques

– be able to apply these principles to any technology

– judge the engineering conformance of technologies

� Recommended Literature:

– Jalote, P.: “A Concise Introduction to Software Engineering”, Springer London, 2010.

– Jalote, P.: “An Integrated Approach to Software Engineering”, 3nd Edition, Springer-Verlag, 2005.

– Sommerville, I.: “Software Engineering”, 9. Edition, Addison Wesley, 2010.



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product

Product Model- Virtual Product Model for Software Development?

Problem-Description

Unit-Requirements

Developer-Requirements

System-design

User-Requirements

Unit-design

Units(Code)

ExecutableUnits

ExecutableSystem

UsableSystem

Used System

Sys

tem

Req

uire

men

ts D

escr

iptio

n

Sys

tem

-Des

ign-

Des

crip

tion

Sof

twar

eU

nit P

rodu

cts

Sof

twar

e S

yste

m P

rodu

cts

Sof

twar

e A

pplic

atio

n P

rodu

cts



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Software Application Engineering Reference Document s

� Application Name:– Owner:– Version:– Last Update:

� Problem Description

� User Requirements/Specification– Functional (use case diagrams, scenarios)– Non-Functional– Inverse– Design decisions– Traceability Matrix

� Developer Requirements– Functional (class/sequence/collaboration/state diagrams)– Non-Functional– Inverse– Design decision– Traceability Matrix

� Requirements Verification (2)� Requirements Validation (2)



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Software System Engineering Reference Documents

� System Name:

– Owner:

– Version:

– Last Update:

� [Developer Specification]

– Functional

– Non-Functional

– Inverse

– Design decisions

� System Design

– Overall design (class/sequence/collaboration/state diagrams)

– Traceability Matrix

– Unit Requirements (n)

→ Exports

→ Imports

� System Verification

� System Validation



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Software Unit Engineering Reference Documents

� Unit Name:

– Owner:

– Version:

– Last Update:

� [Unit Specification]

– Functional

→ Exports

→ Imports

– Non-Functional

– Inverse

– Design decisions

� Unit Implementation

– Unit design (data/algorithm)

– Unit Code

– (Traceability)

� Unit Verification

� Unit Validation



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Virtual vs Real Products- Many different Mappings?

� In Practice:

– Any virtual product may be omitted (justification!).

– Any mapping onto real products exist.

Problem descriptionLastenheftLastenheft

User requirements

Developer requirements

System design

Unit requirements

Unit design

Unit code

PflichtenheftPflichtenheft

SystembeschreibungSystembeschreibung

Source code filesSource code files



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Virtual vs. Real Products- SW vs. System Engineering?

Problem-Description

Unit-Requirements


System-design

User-Requirements

Unit-design

Units(Code)

System- UserRequirements

System-Dev.Requirements

SystemDesign

(Software) User-Requirements



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Reverse- /Re-/Forward Engineering

Problem-Description

Unit-Requirements


System-design

User-Requirements

Unit-design

Units(Code)

ExecutableUnits

ExecutableSystem

UsableSystem

Used System

Sys

tem

Req

uire

men

ts D

escr

iptio

n

Sys

tem

-Des

ign-

Des

crip

tion

Sof

twar

eU

nit P

rodu

cts

Sof

twar

e S

yste

m P

rodu

cts

Sof

twar

e A

pplic

atio

n P

rodu

cts



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Reverse-/ Re-/Forward Engineering

Problem-Description

Unit-Requirements


System-design

User-Requirements

Unit-design

Units(Code)

ExecutableUnits

ExecutableSystem

UsableSystem

Used System

Sys

tem

Req

uire

men

ts D

escr

iptio

n

Sys

tem

-Des

ign-

Des

crip

tion

Sof

twar

eU

nit P

rodu

cts

Sof

twar

e S

yste

m P

rodu

cts

Sof

twar

e A

pplic

atio

n P

rodu

cts

???



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Reverse-/Re-/ Forward Engineering

Problem-Description

Unit-Requirements


System-design

User-Requirements

Unit-design

Units(Code)

ExecutableUnits

ExecutableSystem

UsableSystem

Used System

Sys

tem

Req

uire

men

ts D

escr

iptio

n

Sys

tem

-Des

ign-

Des

crip

tion

Sof

twar

eU

nit P

rodu

cts

Sof

twar

e S

yste

m P

rodu

cts

Sof

twar

e A

pplic

atio

n P

rodu

cts



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



General Development Model- What is the role of any document?

� Goal for Product Xi

– Readily useable for developing the product of level (i+1)

– Easily changeable (including effects on level (i+1))

– Easily verifiable against level (i-1)

– Easily useable as a reference document for verification and validation

Xi+1

Xiex

Is validated againstXi



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Forms of Refinement

� The “is developed into” relationship involves the a ddition of information to the lower layer to realize the upper layer

� There are four main forms of additions (refinements ):

– Decomposition ( Aggregation)→ Breaking a large entity into smaller parts (e.g., system consists of units)→ Complete or incomplete refinement?→ Abstraction?

– Specialization (Generalization)→ Creating a specific variant (e.g., room (square meters))→ Inherits characteristics of parent

– Formalization → Representing an entity in a more formal form (e.g., informal requirements as use

cases)

– Completion→ Adding information that was missing at the level above (e.g., algorithmic design

to code)



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 1- Easy to understand

� Easy to Understand

– Tailored notation (towards stake-holders, appropriate mathematics)

– Tailored decomposition techniques

– Completeness

– Consistency



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 2- Divide and Conquer

� Divide and Conquer

– Decomposition approach

→ Types of “units” (e.g. classes in OO)

→ Types of relationships (e.g. method invocation in OO)

→ Different views (e.g. in UML)

– Characteristics of good decomposition

→ Each decomposed unit must be understood completely (no implicit knowledge necessary)

� All exports & imports known

� No implicit dependencies

→ Minimal coupling

→ Maximum cohesion

→ Maximum information hiding (e.g., changes of implementation of a unit does not affect unit specification; change of developer requirement affects ONE unit only)

→ Decomposition is complete (see Principle P3)

→ Verification can be done incrementally



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 3- Level Completness

� Level Completeness (of refinements)

– Lower level is complete refinement & upper level is complete abstraction

– Enables stepwise, incremental verification

– Reduces rework via constant feedback



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 4 - Horizontal Traceability

� Horizontal Traceability

– With respect to a given product, on a given abstraction level

→ Relationships between the elements in a given view must be explicitly documented (= local horizontal traceability) (e.g., data & activities in an activity diagram)

→ Relationships between elements of different views must be explicitly documented (= global horizontal traceability) (e.g., different diagram types in UML)



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 5- Vertical Traceability

� Vertical Traceability

– With respect to two products at adjacent abstraction levels

→ Relationships between refined elements within one product of our reference product model (= local vertical traceability) (e.g., functional refinements (see: chapter 4))

→ Relationships between refined elements of different products of our reference product model (= global vertical traceability) (e.g., refinements of developer requirements into designs (see: chapter 5))



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 6- Explicit documentation of the "is verified" relati onship

� Explicit documentation of the “is verified” relatio nship

– Scope of the checks (including reading technique, e.g. checklists)

– Results of the checks

– Resulting changes



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Principle 7- Explicit documentation of the “is validated” relatio nship

� Explicit documentation of the “is validated” relati onship

– Scope of the checks (e.g., test strategy, test cases)

– Results of the checks

– Resulting changes



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques



Relation between goals and products- Principles participate to the achievement of goals

� P1 Easy to Understand

� P2 Divide and Conquer

� P3 Level Completeness (of refinements)

� P4 Horizontal Traceability (local/global)

� P5 Vertical Traceability (local/global)

� P6 Explicit Documentation of the “is verified” Relationship

� P7 Explicit Documentation of the Realization Level of the “is validated” Relationship

PRINCIPLES

P1 P2/3 P4 P5 P6 P7

GO

ALS

Easily usable by level (i+1)

X X X

Easily changed X X X X X X

Easily verified against level (i-1)

X X X

Readily usable as a reference document for V & V

X X



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Scope of description techniques

� WHAT?

– For all products of the virtual product model

– Facets of description (interface, behavior)

– Aspects of description (functionality, non-functionality)

� HOW?

– Overview of basic description techniques

– Mapping of basic description techniques to facets & aspects

– Instantiation of basic description techniques into actual description techniques (e.g., UML)



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Views of description

� Interface (external, static facet)

� Behavior (external, dynamic facet)

� Structure (internal, static facet)

� Flows / relationships (internal, dynamic facet)

interface

structure

flow

behavior



�SW System Eng

�SW Unit Eng




�Principles

�G x P Matrix

� Description


�Basic Techniques


Basics of SE –Software Product Basic techniques

Interface Behavior Structure Flow

Natural languages x x x x

Regular expressions x

Data flow graphs x x x

Structure chart x

Control flow graphs x x

Entity relationship diagrams x

Logical/algebraic specification x x

Functional specification x x

Axiomatic specification x

Decision tables x

State diagrams x

Petri Nets x

Class/object diagrams x x

Operational specifications x x

Interaction diagrams x x x

Use case diagrams x x