Software AutomationMarch Managing the Evolution of Reusable Assets Theo D’Hondt Patrick Steyaert Programming Technology Lab Vrije Universiteit Brussel

Software AutomationMarch Activities

Software AutomationMarch Conventional Software Engineering

Software AutomationMarch Software Engineering 1975 A.D.

Software AutomationMarch Software Engineering 1985 A.D.

Software AutomationMarch Recent Insight

Software AutomationMarch Engineering Techniques in Software… Modularity

Software AutomationMarch Modularity

Software AutomationMarch Engineering Techniques in Software… Reuse

Software AutomationMarch Reuse

Software AutomationMarch Software Engineering 1995 A.D.

Software AutomationMarch Development Method

gold coins Reuse assets are the gold coins of software engineering. dirty word Legacy is the dirty word of software engineering.

Software AutomationMarch What can Go Wrong… 4Arian 4 »well tested software »proven correctly 4Arian 5 »reuse of pieces of Ariane 4 software »result: trivial error (floating point error), large consequences 4What happened ? »changed flight specifications

Software AutomationMarch Our Example: Tape Management TapeManipulation accept(Tape) transfer(Tape) manipulate(Tape) TapeManager register(Tape) Tape identification kvu associate(script) manipulates manages 4Tapes are manipulated - adding scripts, visioning 4Tapes are managed - tracking, kvu checking

Software AutomationMarch Tape Components TapeManipulation accept(Tape) transfer(Tape) manipulate(Tape) TapeManager register(Tape) Tape identification kvu associate(script) manipulates manages Visioning manipulate(Tape) Technical Visioning manipulate(Tape) Shipping-Receiving receive(Tape) ship(Tape) Traffic location?(Tape) depends on kvu, script present,... tape manipulation internal to visioning

Software AutomationMarch Composition Problem ! Traffic Technical Visioning Tape

Software AutomationMarch Challenges: Impact Analysis Changing a method

Software AutomationMarch Example TapeManager add(Tape) addAll(TapeSet) OOTVTapeManager add(Tape) TapeManager addAll(TapeSet) add(Tape) addAll(TapeSet) OOTVTapeManager add(Tape) addAll(TapeSet) no notification notify parent class change

Software AutomationMarch Challenges: Proliferation of Versions Repository - Tapemanager - Tapes Application A - MyTapeManager - Tape Application B - MyTape Application C - XTapeManager Maintenance problem: version management Development problem: design for reuse

Software AutomationMarch Challenges: Design for Reuse... ? How to improve reusability? TapeManipulation accept(Tape) transfer(Tape) manipulate(Tape) TapeManager register(Tape) Visioning manipulate(Tape) Traffic location?(Tape)

Software AutomationMarch Reuse Contracts Asset reuser Asset provider 4 declares what assump- tions can be made about the asset 4 declares how an asset can be reused 4 formally, non- coercively 4 declares what assumptions are made about the asset 4 declares how an asset is reused 4 formally,disciplined 4 rules for change propagation

Software AutomationMarch Contracts & Specialisation Clauses implementation will invoke transfer, manip… Contracts declare the assumptions that can be made about a class and how a it can be reused. tm:TapeManager notify(...) m:TapeManip… accept(Tape) transfer(Tape) next:TapeManip… accept(Tape) 3.transfer [notify] 1.accept 4.transfer [accept] 2.accept [manipulate, transfer] manipulate(Tape) tape transfer contract

Software AutomationMarch Evolution and Composition Changing a method

Software AutomationMarch Remember TapeManipulation accept(Tape) transfer(Tape) manipulate(Tape) TapeManager register(Tape) Tape identification kvu associate(script) manipulates manages Visioning manipulate(Tape) Technical Visioning manipulate(Tape) Shipping-Receiving receive(Tape) ship(Tape) Traffic location?(Tape) Composition Problem !

Software AutomationMarch Changing Assumptions TapeManip.transfer [notify] Assumption made by reuser (before change) Traffic Assumes TapeManip.transfer [] What can be assumed (after composition or change) Traffic Actually gets

Software AutomationMarch BUT… Traffic notify(...) TapeManager …concrete parent class … Assumes Too verbose Does not document how TapeManager is actually reused TapeManip.transfer [notify]

Software AutomationMarch Declaring How a Class is Actually Reused documenting different kinds of reuse TapeManager Traffic Refinement 3 notify [+track] TapeManager notify (...) Traffic track notify [track] notify (...) track notify [track]

Software AutomationMarch Different Kinds of Reuse 3Assumption “preserving” »Concretisation: filling in the “hotspots” »Refinement: refining the overall design »Extension: adding new behaviour 3Assumption “breaching” »Abstraction: generalisation »Coarsening: performance optimisation »Cancellation: fixes

Software AutomationMarch Estimating Impact of Changes Coarsening 3 addAll [-add] Refinement 3 add [+notify] Refinement 3 add [+notify] TapeManager add(Tape) addAll(TapeSet) [add] OOTVTapeManager add(Tape) [notify] TapeManager addAll(TapeSet) [add] add(Tape) addAll(TapeSet) [] OOTVTapeManager add(Tape) [notify] addAll(TapeSet) [add] notify # addAll needs to be overridden too

Software AutomationMarch Estimating Composability TapeManager Traffic notify (...) track notify [track] Refinement 3 notify [+track] TapeManipulation Technical Visioning transfer (Tape) [notify] transfer (Tape) [] Coarsening 3 transfer [-notify] tape transfer contract # composition problem

Software AutomationMarch Reuse Contracts for Inheritance Asset reuser Asset provider 3 rules for detecting conflicts TapeManager add() addAll() [add] Refinement  add […] 3 formally 3 non-coercively 3 formally 3 disciplined

Software AutomationMarch Conclusion 4New style of software engineering »modularity  reuse  objects »learn about the problem domain as you go along with projects 4Challenges »supporting reuse »supporting evolution 4Reuse Contracts »incrementally turn software artifacts in assets