metrics for the structural assessment of product line architecture asim rahman [email protected]

Metrics for the Structural Assessment of Product Line Architecture

Asim Rahman

[email protected]

Blekinge Institute of Technology

SE-371 79 Karlskrona

+46 455 38 50 00

www.bth.se/eng

Agenda Introduction

Research Area

Reseach Methodology

Component Based Design

Service Utilization Concept

Structural Soundness

Measuring Strcutural Soundness

Measuring Quality Attributes

Case Study: Library System

Conclusions

Future Work



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Introduction

Software Reuse

Software Product Lines (SPL) as a reuse approach

SA vs SPL Architecture

Variability is Software Systems

Architectural Assessments



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Research Area & Questions

Questions?

How do we judge the qulaity of the structure of the architecture?

How to we quanitfy the Property?

How can this measure be used to build a better Product Line Architecture?

Motivation

Almost no published reseach in the area

Large amount of published papers in component based software engineering

Many PL approaches (KobrA, Jan Bosch, Clements) follow a component based approach



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Research Methodology



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Component Based Design

ComponentComponent is a unit of composition with contractually specified interfacesinterfaces and explicit context context dependenciesdependencies...[Szyperski ’97]



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Service Ultization Concept



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Structural Soundness

components are divideddivided, plannedplanned and then connectedconnected together in most effective way possible to provide a solution to a well defined problem.

SS cannot be gerneralized for all architectures – property should only be compared when two or more architecture provide solution to a similar problem



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Measuring Structural Soundness

Four step model:Research Methodology

Identifying design/architecture properties (L1)

Identifying metrics to measure properties (L2)

Identifying measurable elements (L3)

Validating the metrics (L4)



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Measuring Quality Attributes (i)

Observability

Ease with which a developer can peak into the component and learn about its fuctions

Behavior of the component is observed by read methods corresponding to the the read properties

Customizability

Ability or the extent to which a component can be configured, without changing its code

Writable properties are accessed by writable methods



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Measuring Quality Attributes (ii)

Interface Complexity

Interface Signature

Properties,operations and events

Interface Constraints

Pre-conditions

Post-conditions

Range constraints on properties

Sequence of interface invocations

Interface Packaging and Configurations

Configurations a component can operate in



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Measuring Quality Attributes (iii)

Self Completeness

SC measured by return value

SC measured by parameters



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Measuring Quality Attributes (iv)

Provided Service Utilization

We use only the PSU value in order to determine the resuability of the components



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Measuring Quality Attributes (v)

Maturity

Mature component tend to be more reusable

Less testing effort

Low probability of defects

More familiarity of developers with the component usage

Known behavior in multiple situations

Some characteristics also tend to decrease the probability of reuse

Increase in size

Non-conformance from component model



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Measuring Quality Attributes (vi)

...Maturity

Measures to quantify maturity

# of faults in requirement and design

# of open faults

# of closed faults

Avg. # of days a fault remains

Avg. # of days to close a fault

Avg. age of a fault



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Measuring Quality Attributes (vii)

Modularity

Measured by TREE IMPURITY [Fenton ’97]

Considering Optionality



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Case Study: Library System (i)

Based on Case Study performed by Fraunhofer Institute of Experimental Studies

Product Line of Library Systems (German Libraries)

Limitations of the Case Study

Few details on operation/service (return val & param)

Scarce information on range constraints on properties

Sequence of method invocation was missing

No details of maturity measures

Variabilty was low



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Case Study: Library System (ii)



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Case Study: Library System (iii)

Correlation Analysis of Quality Attributes

Check for mullticollinearity

If strong correlation is found between two quality attributes, then one of the two metrics must be selected

Multicollinearity

Conservative: R ≤ 0.5

Liberal: If relation between variable remain constant, then multicollinearity is not a problem

Jenson: R ≤ 0.9

Reasons:Reasons:

1.1. Dont want to double countDont want to double count

2.2. Dont expect to have large data Dont expect to have large data pointspoints

3.3. Carefully categorized quality Carefully categorized quality attributes; hence slight indication of attributes; hence slight indication of correlation is alarmingcorrelation is alarming



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Case Study: Library System (iv)

Analysis Test Selection

Analysis of Component Level Metrics



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Case Study: Library System (v)

Analysis of the Architecture Level Metrics



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Case Study: Library System (vi)

Wilcoxon Signed Rank Test

SCp and SCr (W = 36, N = 8)

Level of Significance = 0.005 (Directional Test)

PSU and SCr (W = 0, N = 3)

For sample sizes smaller than N=5 there are no possible values of W that would be significant at or beyond the baseline 0.05 level

CICM and SCr (W = 10, N = 9)

Level of Significance > 0.05 (Directional Test)



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Conclusion

Structural Assessment of Product Lines can make use of Component Based Metrics

Adaptation requires consideration of PLA specific features, variability and optionality

Aggregated value as well as individual metrics are usefull for the architects

The metrics need to be validated further by studying industrial Product Lines



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Future Work

Infuence towards overall quality

Degree of Relation

Unavailability of Product Line Architecture



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Questions?

metrics for the structural assessment of product line architecture asim rahman [email protected]

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