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INGINERIE SOFTWARE. Ştefan Stăncescu. CURSUL 2.2 Legile lui Lehman. CURSUL 2.2- LEGILE LUI LEHMAN. I - Continuing Change II - Increasing Complexity III - Self Regulation IV - Conservation of Organisational Stability V - Conservation of Familiarity VI - Continuing Growth - PowerPoint PPT Presentation
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INGINERIE SOFTWARE
Ştefan Stăncescu
CURSUL 2.2
Legile lui Lehman.
INGINERIA SOFTWARE StSt 2
CURSUL 2.2- LEGILE LUI LEHMAN
I - Continuing Change
II - Increasing Complexity
III - Self Regulation
IV - Conservation of Organisational Stability
V - Conservation of Familiarity
VI - Continuing Growth
VII - Declining Quality
VIII - Feedback System
INGINERIA SOFTWARE StSt 3
CURSUL 2- LEGILE LUI LEHMAN
I - Continuing Change
A program that is used must be continually adapted else it becomes progressively less satisfactory
Un produs program software PPSW operational
trebuie continuu adaptat
altfel devine
din ce in ce mai putin eficient
(realitatea initiala la t=0 se modifica in t)
INGINERIA SOFTWARE StSt 4
CURSUL 2- LEGILE LUI LEHMAN
II - Increasing Complexity
As a program is evolved its complexity increases unless work is done to maintain or reduce it.
Daca un PPSWevolueaza
complexitatea sa creste
deci trebuiesc activitati de a
mentine sau reduce complexitatea
(termodinamica modificarilor – entropia creste, modificarile se suprapun – reproiectare tot)
INGINERIA SOFTWARE StSt 5
CURSUL 2- LEGILE LUI LEHMAN
III - Self Regulation
The program evolution process is self regulating with close to normal distribution of measures of product and process attributes
Procesul de evolutie al unui PPSW este autoreglabil, legat de distributia uniforma a
facilitatilor modificate ale PPSW
parametrilor facilitatilor PPSW
(Cantitatea de facilitati se ofera constant in timp)
INGINERIA SOFTWARE StSt 6
CURSUL 2- LEGILE LUI LEHMAN
IV - Conservation of Organisational Stability
The average effective global activity rate on an evolving system is invariant over the product life time.
Activitatea de modificare a evolutiei unui PPSW este constanta in medie
pe tot ciclul de viata al PPSW
(cantitatea de efort organizational se pastreaza)
INGINERIA SOFTWARE StSt 7
CURSUL 2- LEGILE LUI LEHMAN
V - Conservation of Familiarity
During the active life of an evolving program, the content of successive releases is statistically invariant
In ciclul de viata operationala a unui PPSW
continutul nou al versiunilor succesive
este invariant statistic
(cantitatea de nou e constanta)
INGINERIA SOFTWARE StSt 8
CURSUL 2- LEGILE LUI LEHMAN
VI - Continuing Growth
Functional content of a program must be continually increased to maintain user stisfaction over its lifetime
Facilitatile unui PPSW trebuiesc mereu mărite
pentru a mentine satisfactia utilizatorului
cat mai mult timp
(mereu trebuie sa se ofere facilitati in plus sau imbunatatite)
INGINERIA SOFTWARE StSt 9
CURSUL 2- LEGILE LUI LEHMAN
VII - Declining Quality
Programs will be perceived as of declining quality unless rigorously maintained and adapted to a changing operational environment
Se va sesiza descresterea calitatii PPSW
daca nu este bine
mentinut si adaptat
dupa schimbarea environmentului
INGINERIA SOFTWARE StSt 10
CURSUL 2- LEGILE LUI LEHMAN
VIII - Feedback System
Programming Processes constitute Multi-loop, Multi-level Feedback systems and must be treated as such to be successfully modified or improved
Procesul de creare/instalare/operare/mentenanta
e sistem cu multe bucle de reactie
si este el insusi modificabil
pentru a mentine adaptarea
INGINERIA SOFTWARE StSt 11