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Formalizing and Analyzing Feature models in Alloy
Jing Sun
Computer Science
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Outline
= Feature modeling
= The Alloy language
= Formalizing feature diagram
= Checking feature models
= Conclusion and future work
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Feature & Feature Modeling
= Conceptual modeling perspective– an important property of a concept– allows to express the commonalities and differences
between concept instance
= Domain engineering context– represents reusable, configurable requirements
= Feature modeling– is the activity of modeling the common and the variable
properties of concepts and their inter-dependencies and organizing them into a coherent model
– feature model diagram
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Feature & Software Engineering
= Feature-oriented programming (Prehofer, 1997)– Can programs be created by composing features?– Next generation of OO programming?
= Feature and advanced separation of concern– Feature is regarded as one dimension of concern (Tarr et al.,
1999)– Can we separate feature concerns from other concerns?
= Feature and software evolution and maintenance– Locating features from source code (Eisenbarth, 2003)– Understanding the implementation of certain features in
programs
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Feature & Software Engineering
= Feature and requirements engineering– Representing and structuring the problem domain as
features– A well known problem: Feature interaction in
telecommunication domain (Zave, 1993)
= Feature and software process– Feature-driven development: an agile, highly adaptive,
software development process (Palmer and Felsing, 2002)
= Feature and software reuse– FORM (Feature-Oriented Reuse Method) (Kang et al., 1998) – Modeling a software product line’s commonalties and
variability in terms of features
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Our current interest
= Analyzing features and their relationships, organizing them into feature model
= Representing feature models
= Formalizing feature models
= Analyzing and verifying feature models
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Feature modeling
= Basic relations among features– One feature may depend on another feature– One feature may exclude another feature
= Feature Types– Mandatory features: must be included in the description
of a concept instance– Optional features: may be included in the description of a
concept instance– Or features: may have any non-empty subset of the or-
features included in the description of a concept instance– Alternative features: …
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Feature diagram example
= A car concept feature diagramCar
Transmission Engine
Automatic Manual
Car BodyPulls trailer
Electric Gasoline
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Applying formal methods
= Alloy – a light-weight formal modeling language
– Based on first order predicate logic
– A subset of Z
– Support automatic analysis
= Applying Alloy to feature modeling– Formalizing a feature model
– Checking a feature model (e.g., checking valid/invalid combination of features, semantic equivalence, …)
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Feature language in Alloy
sig Feature {} // define a set of features
disj sig Concept extends Feature { // define a concept
holds : set Feature // all possible configuration of a concept
}
// Depends - The selection of f2 depended on the selection of f1
fun Depends(c:Concept, f1:Feature, f2: Feature) {
f1 in c.holds => f2 in c.holds
}
// Alternative feature type
fun Alternative(c:Concept, pf:Feature, s:set Feature) {
all f : s | Excludes(f, s-f) && Depends(f, pf)
pf in c.holds => one f : s | Depends(pf, f)
} …
}
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Feature model in Alloy
open feature/FeatureModel
static disj sig Automatic extends Feature{}
static disj sig Manual extends Feature{}
static disj sig CarBody extends Feature{}
…
static disj sig Car extends Concept{}
fact {Mandatory(Car, Car, CarBody+Transmission+Engine)}
fact {Optional(Car, Car, PullsTrailer)}
fact {Alternative(Car, Transmission, Automatic+Manual)}
fact {Or(Car, Engine, Electric+Gasoline)}
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Checking & analyzing feature models
= Checking valid/invalid feature configurations– assert correctness { all c : GPL | c.holds != GPL + Algorithm +
Connected + Search + BFS + Graph + Undirected + Weighted }
= Checking the source of unsatisfiability using “core extension”
= Checking the solvability of feature models
= Analyzing semantic equivalence of feature models
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Checking & analyzing feature models
= Semantic equivalence checking
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Conclusion & future work
= Defined a formal semantics for the feature modeling language in Alloy
– Provide a precise and rigorous formal basis for the feature diagram
– Identify basic relations in feature diagram and showed that other complex relations can be expressed as a combination of the two
= Checking feature models using Alloy analyzer.
= Dynamic feature model re-configurations– Feature interaction problem
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Questions?
Jing SunComputer Science
