Product Metrics by ravi

7/30/2019 Product Metrics by ravi

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Ravi varma


2/23

Software quality:Conformance to

explicitly stated functional and

performance requirements, explicitly

documented development standards, andimplicit characteristics that are expected

of all professionally developed software.


3/23

McCalls Quality Factors

Factors that affect software quality can be categorized in two broad groups:

1. Factors that can be directly measured (e.g. defects uncovered during testing)

2. Factors that can be measured only indirectly (e.g. usability or maintainability)

McCalls quality factors

1. Product operation(operational characteristics)

a. Correctness

b. Reliability

c. Efficiency

d. Integrity

e. Usability

2. Product Revision(ability to undergo change)

a. Maintainability

b. Flexibility

c. Testability

3. Product Transition(adaptability to new

environment)a. Portability

b. Reusability

c. Interoperability


4/23

ISO 9126 Quality Factors

1.Functionality

2.Reliability

3.Usability

4.Efficiency

5.Maintainability

6.Portability


5/23

Product metrics for computer software helps usto assess quality.

Measure

-- Provides a quantitative indication of the extent,

amount, dimension, capacity or size of someattribute of a product or process

Metric(IEEE 93 definition)

-- A quantitative measure of the degree to which asystem, component or process possess a given

attribute Indicator

-- A metric or a combination of metrics thatprovide insight into the software process, asoftware project or a product itself


6/23

Product metrics for the Analysis model

Function point Metric

First proposed by Albrecht

Measures the functionality delivered by thesystem

FP computed from the following parameters

1. Number of external inputs(EIS)

2. Number external outputs(EOS)3. Number of external Inquiries(EQS)

4. Number of Internal Logical Files(ILF)

5. Number of external interface files(EIFS)


7/23


8/23

To compute function points(FP) the following

relationship is used.

FP = count total x [0.65 + 0.01 x (Fi)]

Fi= 1 to 14 are value adjustment factor(VAF)based on these 14 questions

For questions go through textbook

For each question there is 1 to 5 value on

average we take 3 for each question.

So generally we take Fi =42.


9/23

Metrics for Specification Quality

we assume that there are nr requirements in a

specification, such that

nr= nf+ nnfnf= number of functional requirements

nnf= number of non-functional requirements

specificity Q1 = nui/n

rnui is the number of requirements for which all

reviewers had identical interpretations

Completeness Q2 = nu/[ni X ns]


10/23

Architectural Design Metrics

Card and Glass define three software designcomplexity measures : structural complexity, datacomplexity, and system complexity.

Structural complexity of a module i is defined in thefollowing manner:

S(i)=f2out(i)

Data complexity provides an indication of thecomplexity in the internal interface for a module i

and is defined asD(i)= v(i)/[fout (i)+1]

Fout (fan-out) indicates the number of modules imme-diately subordinate to module i; that is, the numberof modules that are directly invoked by module i.


11/23

system complexity is defined as the sum ofstructural and data complexity, specified as

C(i)= S(i)+ D(i)

Fenton suggests a number of simple morphology

Size = n + a

n is number of nodes

a is number of arcs

r= a/n

depth = the longest path from the root (top) nodeto a leaf node.

Width = maximum number of nodes at any onelevel of the architecture


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13/23

DSQI(Design Structure Quality Index) US airforce has designed the DSQI

Compute s1 to s7 from data and architecturaldesign

S1:Total number of modules

S2:Number of modules whose correct function depends onthe data input

S3:Number of modules whose function depends on priorprocessing

S4:Number of data base items

S5:Number of unique database items

S6: Number of database segments

S7:Number of modules with single entry and exit


14/23

Calculate D1 to D6 from s1 to s7 as follows:

D1=1 if standard design is followed otherwise D1=0

D2(module independence)=(1-(s2/s1))

D3(module not depending on prior processing)=(1-(s3/s1))

D4(Data base size)=(1-(s5/s4))

D5(Database compartmentalization)=(1-(s6/s4)

D6(Module entry/exit characteristics)=(1-(s7/s1))

DSQI=sigma of WiDi


15/23

Metrics for object-oriented design-Size

Size is defined in terms of four views: population, volume, length, andfunctionality

Complexity

How classes of an OO design are interrelated to one another How classes of an

OO design are interrelated to one another Coupling

The physical connections between elements of the OO design The physicalconnections between elements of the OO design

Sufficiency

the degree to which an abstraction possesses the features the degree to whichan abstraction possesses the features required of it, or the degree to which a

design component required of it, or the degree to which a design componentpossesses features in its abstraction, from the point of view of possessesfeatures in its abstraction, from the point of view of the current application.

Completeness

An indirect implication about the degree to which the abstraction An indirectimplication about the degree to which the abstraction or design componentcan be reused


16/23

-Cohesion

The degree to which all operations workingtogether to achieve a single, well-definedpurpose

PrimitivenessApplied to both operations and classes, the degreeto which an operation is atomic

Similarity

The degree to which two or more classes are

similar in terms of their structure, function,behavior, or purpose

-volatility

The degree to which the likelihood that a changewill occur


17/23

Class oriented metrics- CK metrics suite

Proposed by Chidamberand Kemerer

weighted methods per class(WMC)

complexity of n methods is c1.. Cn of classfor WMC = ci

depth of the inheritance tree(DIT)

number of children(NOC)

coupling between object classes(CBO)

response for a class(RFC)

lack of cohesion in methods(LCOM)


18/23

Class-Oriented Metrics The MOOD Metrics

Suite( go through text book)

Method inheritance factor(MIF)

Coupling factor

Operation-Oriented Metrics

proposed by Lorenz and Kidd

average operation size

operation complexity

average number of parameters per

Operation


19/23

Component-Level Design MetricsCohesion metrics: afunction of data objects

and the locus of their definition

Coupling metrics :a function of input and

output parameters, global variables, and

modules called

Complexity metrics :hundreds have been

proposed (e.g., cyclomatic complexity)

Interface Design MetricsLayout appropriateness:a function of layout

entities, the geographic position and the

costofmaking transitions among entities


20/23

HSS(Halstead Software science) Primitive measure that may be derived after the code

is generated or estimated once design is completen1 = the number of distinct operators that appear in a

program

n2 = the number of distinct operands that appear in aprogramN1 = the total number of operator occurrences.N2 = the total number of operand occurrence.Overall program length N can be computed: N = n1 log2 n1 + n2 log2 n2Program volume V = N log2 (n1 + n2)

Volume ratio

L= 2/n1 X n2/N2


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n1 = the number of distinct operators that

appear in a program n2 = the number of distinct operands that

appear in a program

N1 = the total number of operatoroccurrences.N2 = the total number of operand

occurrence.

Program Level and Effort

PL = 1/[(n1 / 2) x (N2 / n2 l)]

e = V/PL


22/23

Metrics for object-oriented testing

Lack of cohesion in methods (LCOM).

Percent public and protected (PAP).Public access to data members (PAD).

Number of root classes (NOR).

Fan-in (FIN).Number of children (NOC) and depth of the

inheritance tree (DIT).


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Mt = the number of modules in the currentrelease

Fc = the number of modules in the currentrelease that have been changed

Fa = the number of modules in the currentrelease that have been added.Fd = the number of modules from the

preceding release that were deleted inthe current release

The Software Maturity Index, SMI, isdefined as:

SMI = [Mt (Fc + Fa + Fd)/ Mt ]

Product Metrics by ravi

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