Lectures on the 6

8/16/2019 Lectures on the 6

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CSE584: Software EngineeringLecture 6 (November 10, 1998

!avi" Not#in!e$t% of Com$uter Science & Engineering

'niverit) of *a+ingtonwww%c%wa+ington%e"ue"ucationcoure584Current-tr


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.+i wee# an" ne/t

e2uirement an" $ecification3 er+a$ more accurate), at+oug+ confuing, it

+ou" be re2uirement $ecification7 an"$ecification7

t t+e +ig+et eve, t+i to$ic focue on3 +ow to "etermine w+at a oftware )tem i u$$oe"

to "o an"

3 +ow to write t+at "own eca ic+ae ac#on; comment on w+at7 v% +ow7


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.o"a) )ou;ve area") een

ot of ic+ae ac#on3


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Caveat

.+ere +a been broa" agreement (wit+in t+e tu"ent int+i ca, a we a ot+er t+at a common $robem inoftware engineering i i>"efine" re2uirement (an"intabe one, too

.+e a$$roac+ ac#on ue to attac# t+i 2uetion in;tgoing to be ea) for ome of )ou to waow3


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o+n @a (S)(temantic(

Arom ac#on (of coure

.o t+oe *it+in a S)tem, .+e Buti"e

eait) .en" to ae an" !ia$$ear%7


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Comment on vi"eo


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few more e/am$e


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mbiguit)

(ou; +ave )our ownfavorite aong t+eeine


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Fut we;re not "one

.+e formaiGation ti eave unanwere"2uetion3 !o "og +ave to wear +oe

3 *+at are +oe !og *+at "oe it mean to wear+oe

3 *+) "o t+e formaiGation a) "og are carrie"7an" +oe are worn7 w+ie t+e ign a) mut be7

.+e formaiGation are in in"icative moo" .+e ign are in o$tative moo"


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Notkin (c) 1997, 1998 10

"og7 (noun

BE! +a 15 "efinition (11H wor" in fu "efinition *ebter; 11 "efinition incu"e

3 a +ig+) variabe "ometic mamma (Cani famiiari coe)reate" to t+e common wof

3 a wort+e $eron3 an) of variou uu% im$e mec+anica "evice for +o"ing,

gri$$ing, or fatening t+at conit of a $i#e, ro", or bar

3 AEE.

3 an invetment %%% not wort+ it $rice3 an unattractive gir or woman


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+oe7 (noun, *ebter;

Si/ "efinition incu"ing3 an outer covering for t+e +uman foot uu% ma"e of eat+er

wit+ a t+ic# or tiff oe an" an attac+e" +ee

3 anot+erI $ace, function, or view$oint

3 a "evice t+at retar", to$, or contro t+e motion of anobDect

3 a "evice (a a ci$ or trac# on a camera t+at $ermitattac+ment of acceor) item

3 a "eaing bo/ "eigne" to +o" evera "ec# of $a)ingcar"


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Carit) i +ar" an" crucia

*e a #now t+i, but ac#on +e$ u t+in# about itmore cear)3 oo"

3 !eignation v% "efinition !eignation are t+e atomic $+enomena

3 e%g%, genetic mot+er

!efinition "efine term in term of "eignation an" ot+er $reviou)"efine" "ecri$tion

3 e%g%, genetic c+i" of

efutabe "ecri$tion can in $rinci$e be "i$roven ∀m,x•Mother(x,m)→¬Mother(m,x)

3 Can;t "o t+i wit+ "efinition


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oo" mi/ing

• The lift never goes from the nth to the n+2nd floor without passing the n+1st

floor

• The lift never passes a floor for which the floor selection light inside the life is

illuminated without stooped at that floor

• If the motor polarity is set to up and the motor switch setting is changed from

off to on, the lift starts to rise without 250 msecs.

• If the upwards arrow indicator at a floor is not illuminated when the lift stopsat the floor, it will not leave in the upwards direction.

• The doors are never open at a floor unless the lift is stationary at that floor.

• hen the lift arrives at a floor, the lift!present sensor at the floor is set to on.

• If an up call "utton at a floor is pressed when the corresponding light is off,

the light comes on and remains on until the call is serviced "y the liftstopping at that floor and leaving in the upwards direction


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rinci$e of uniform moo"


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*i7 an" S+a7

Some government grou$ write re2uirement wit+$ecifie" meaning for wi7 an" +a7 an" ma)7an" uc+3 +a7 i a re2uirement

3 ma)7 i an o$tiona re2uirement3 wi7 "ecribe omet+ing not un"er contro of t+e

)tem

Not awa) too cear3 eate" to moo" mi/ing


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Structure" re2uirement

<3


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Aorma met+o"

.+e origina ue of formaim in oftwareengineering wa for $roving t+e e2uivaencebetween a $ecification an" an im$ementation3 .+i +a" a number of $robem

Fut t+ere +a been a reurgence of interet informa met+o"3 ot) "ue to $otentia uefune in $ecification

3 n" a few ucce torie


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otentia benefit


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St)e of $ecification

o"e>oriente" (e%g% , O! gebraic (e%g% BF, Larc+

roce o"e (e%g% CCS, CS

Ainite tate>bae" (e%g% Statec+art, SL Logica, contructive, muti>$ara"igm, broa"

$ectrum, %%%


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o"e oriente"

o"e a )tem b) "ecribing it tatetoget+er wit+ o$eration over t+at tate3 n o$eration i a function t+at ma$ a vaue of t+e

tate toget+er wit+ vaue of $arameter to t+e

o$eration onto a new tate vaue mo"e oriente" anguage t)$ica) "ecribe

mat+ematica obDect (e%g% "ata tructure orfunction t+at are tructura) imiar to t+ere2uire" com$uter oftware


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i"e: ac#on

Arom a $ecification of a ma tee$+one)tem– “a s"#scri#er is a se$"ence of digits% &et

Subs #e the set of all s"#scri#ers

%%%certain digit se$"ences corres'ond to"no#taina#le n"m#ers, and some are neither

s"#scri#ers, nor are they "no#taina#le%

Bn) a mat+ematician cou" treat t+e reawor" wit+ uc+ au"aciou "i"ain%7 Pac#on


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gebraic $ecification

e$reent tructure a agebra3 e$reent reut a com$oition of o$eration,

not a e/$icit tate

3 Coe) reate" to !.

gebraic met+o" ten" to $rovi"e eim$ementation bia t+an ome ot+ermet+o"


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roce bae" $ecification

Aor "ecribing concurrent )tem o agebraic in nature, but focu on

$rocee t+at can be com$oe" over a

variet) of o$erator (uc+ a run in $arae


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Ainite tate $ecification

e$reent )tem a a finite tate mac+ine .ranition fire" b) e/terna (an" ma)be interna

event

Bften uefu in "ecribing a$ect of embe""e")tem3


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Ne/t wee#

Ne/t wee#

Lectures on the 6

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