Suppo ing Requi emen s Ve i ica ion Using XSLT

Amado Du án An onio Ruiz–Co és Ra ael Co chuelo Miguel To o
Dp o. de Lenguajes y Sis emas In o má icos
Uni e sidad de Se illa
{amado ,a uiz,co chu,m o o}@lsi.us.es
Abs ac
In his pape we p esen a ligh -weigh app oach o
he au oma ic e i ica ion o equi emen s. This app oach
is no based on na u al language pa sing echniques bu
on he ep esen a ion o equi emen s in XML. In ou ap-
p oach, XSLT s yleshee s a e used no only o au oma i-
cally gene a e equi emen s documen s, bu also o p o ide
e i ica ion–o ien ed heu is ics as well as o measu e he
quali y o equi emen s using some e i ica ion–o ien ed
me ics. These ideas ha e been implemen ed in REM, an ex-
pe imen al XML–based equi emen s managemen ool also
desc ibed in his pape .
1. In oduc ion
I is widely acknowledged wi hin he so wa e commu-
ni y ha equi emen s quali y is one o he mos impo -
an ac o s in he quali y and o e all success o so wa e
p ojec s. Tha is he eason why some equi emen s engi-
nee ing (RE) ac i i ies ha e as hei main goal inc easing
he quali y o equi emen s, namely equi emen s analysis,
equi emen s e i ica ion and equi emen s alida ion (see
he UML ac i i y diag am in igu e 1).
Requi emen s Quali y Assu ance
<<subp ocess>>
Requi emen s Enginee ing
<<p ocess>>
Requi emen s Nego ia ion
<<subp ocess>>
Requi emen s Managemen
<<subp ocess>> Requi emen s Valida ion
Requi emen s Ve i ica ion
Requi emen s Analysis
Requi emen s Elici a ion
<<subp ocess>>
Figu e 1. RE p ocess model
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This wo k is pa ially suppo ed by he CICYT p ojec TIC 2000–
1106–C02–01 (GEOZOCO) and by he CYTED p ojec VII.18 (WEST)
These quali y–o ien ed ac i i ies ac as a equi emen s
quali y il e in a simila way he quali y ga eway does in
he Vole e me hod [16]. The main goals o hese ac i i ies
a e summa ized in able 1.
Table 1. Quali y–o ien ed RE ac i i ies
Ac i i y Main goal
Analysis Iden i y con lic s in equi emen s
Ve i ica ion De ec de ec s in equi emen s
Valida ion Ce i y equi emen s a e consis en wi h he in-
en ions o cus ome s and use s
In his pape we ocus on au oma ic e i ica ion o so–
called speci ica ion e o s [8] and in assis ing he equi e-
men s e i ie in de ec ing knowledge e o s [8] by means
o some e i ica ion–o ien ed heu is ics and equi emen s
me ics ha can be easily compu ed. Ou app oach is based
on he eme gen echnology buil a ound XML [22] and i s
companion language XSLT [21], as ini ially desc ibed in
[7].
The es o he pape is o ganized as ollows. Fi s , we
desc ibe REM, ou RE ool [5, 6]. Then, we p esen a b ie
o e iew o he XML model o equi emen s used by REM
and how XSLT can be used o suppo he e i ica ion o
some quali y p ope ies o equi emen s exp essed in XML.
Finally, we discuss some ela ed wo k and poin ou conclu-
sions and u u e wo k.
2. REM: an XML–based equi emen s ool
REM (REqui emen s Manage ) is an expe imen al RE
ool de eloped by one o he au ho s as pa o his PhD. The-
sis [5]. A REM p ojec is conside ed o be composed o he
ou documen s co esponding o he ou abbed ee iews
in igu e 2. In REM, equi emen s, con lic s and de ec s a e
exp essed in na u al language using p ede ined empla es
and some linguis ic pa e ns (see [6] o de ails). Fo ex-
p essing concep ual models, we ha e chosen a subse o he
UML [3].
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1090-705X/02 $17.00 © 2002 IEEE
C ea ion oolba
HTML iew
Tabbed ee iews
Con ex menu
Requi emen s
Concep ual
Models
De ec s and
Con lic s
Change
Reques s
Figu e 2. REM use in e ace (de aul XSLT s yleshee )
2.1. REM a chi ec u e
REM p ojec s a e s o ed in ela ional, ligh –weigh da a-
bases. When he use c ea es a new REM p ojec , he basic
s uc u e is aken om a base p ojec , ha can be emp y
o can con ain he manda o y sec ions o equi emen s s an-
da ds like [9]. Any o dina y REM p ojec can be selec ed
as a base p ojec , so REM use s can euse whole REM
p ojec s o only indi idual equi emen s by means o he
copy&pas e and d ag&d op ea u es o he REM use in e -
ace.
In o de o p o ide immedia e eedback on use ac ions,
REM gene a es XML da a co esponding o he p ojec be-
ing edi ed, applies an ex e nal XSLT s yleshee ha ans-
o ms XML da a in o HTML and shows he esul o he
use . The use can change documen appea ance o con en
by selec ing o c ea ing di e en XSTL s yleshee s. The de-
aul XSLT s yleshee gene a es a highly hype linked docu-
men , easing na iga ion o equi emen s documen s.
2.2. REM use in e ace
The use in e ace o REM p esen s wo di e en iews
o he use (see igu e 2). On he le , he use can see ou
abbed ee iews, one o each documen in he p ojec . On
he igh , he esul o he XSLT ans o ma ion o he XML
da a co esponding o he selec ed documen is p esen ed o
he use in a embedded web b owse .
In any o he ou ee iews, he use can di ec ly ma-
nipula e REM objec s by d ag&d op o by con ex menus.
Only ac ions ha make sense can be pe o med, ollowing a
co ec –by–cons uc ion app oach, hus inc easing in e nal
consis ency [8] and sa ing e i ica ion e o . Fo example,
ac ions o use case s eps can be o h ee di e en classes
(see igu e 3): ac o ac ion, i he ac ion is pe o med by an
ac o ; sys em ac ion i he ac ion is pe o med by he sys-
em, o use case ac ion, i he ac ion consis s o pe o ming
ano he use case, i.e. ainclusion o ex ension [3]. S eps wi h
ac o ac ions o use case ac ions can be c ea ed only i some
ac o o ano he use case ha e been p e iously c ea ed. On
he o he hand, only ac o s o use cases no e e enced by
any s ep can be dele ed.
3. XML model o equi emen s in REM
REM is based on a UML model o equi emen s de-
sc ibed in [5] which has been ansla ed in o a Documen
Type De ini ion (DTD) [22]. As an example, he UseCase
class in igu e 3 has been ansla ed in o he ollowing DTD
elemen de ini ion:
<!ELEMENT em:useCase (
em:name, em: e sion,
em:au ho s?, em:sou ces?, em:commen s?,
em:impo ance, em:u gency, em:s a us, em:s abili y,
em:isAbs ac ?, em: igge ingE en ,
em:p econdi ion, em:pos condi ion,
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em: equency, em:s ep*
)>
<!ATTLIST em:useCase oid ID #REQUIRED>
whe e he em:useCase elemen , as any o he REMObjec ,
mus ha e a equi ed iden i ica ion a ibu e called oid. Chil-
d en elemen s o em:useCase like em: igge ingEe en o
em:p econdi ion con ain only ex , i.e. na u al language. In
REM, ex can be composed o any combina ion o ee ex ,
e e ences o o he objec s and TBD (To Be De e mined)
ma ks, de ined as ollows:
<!ELEMENT em: ex (#PCDATA| em: e | em: bd)*>
<!ELEMENT em: e (#PCDATA)>
<!ATTLIST em: e oid IDREF #REQUIRED>
<!ELEMENT em: bd EMPTY>
whe e he em: e elemen mus ha e a equi ed a ibu e
called oid ha i is decla ed as an IDREF,i.e. a e e ence
o ano he elemen wi h a ma ching iden i ica ion a ibu e
alue. The em: bd elemen is decla ed as an EMPTY ele-
men , i.e. i is simply a ma k.
4. Using XSLT o equi emen s e i ica ion
Simply by he ac o using REM, some quali y p ope -
ies desc ibed in [8] like modi iabili y, elec onically s o -
age, e sion anno a ion o being aceable a e au oma ically
name
e sion
commen s
REMObjec
impo ance
u gency
s a us
s abili y
C-Requi emen
isAbs ac
igge ingE en
p econdi ion
pos condi ion
equency
UseCase S ep
*
{o de ed}
0..1
desc ip ion
Condi ion
*
desc ip ion
e mina ion
Excep ion
Ac ion
1..1
1..1
desc ip ion
Ac o Ac ion
desc ip ion
pe o mance
Sys emAc ion
{disjoin }
Ac o
UseCaseAc ion
*
*
1..1
1..1
...
...
{comple e,disjoin }
{comple e,disjoin }
S akeholde
T ace
*
sou ces
*
au ho s
sou ce
1..1
1..1 a ge
Figu e 3. UML model o use cases in REM
ul illed. In he ollowing sec ions we desc ibe how o h-
e s quali y p ope ies desc ibed in [8] can be au oma ically
e i ied, o some heu is ics p o ided, using XSLT when e-
qui emen s a e elec onically s o ed in XML o ma acco d-
ing o heREM DTD.
Al hough i is also possible o apply his app oach o he
e i ica ion o concep ual models c ea ed wi h REM,in his
pape we ocus only on equi emen s. Fo XML–based con-
cep ual model e i ica ion see [13], whe e he xlinki lan-
guage and how i is used o he e i ica ion o UML models
in XMI o ma [14] a e desc ibed.
Fo he sake o eadabili y, all examples in he ollow-
ing subsec ions use he em:useCase elemen p e iously
desc ibed, al hough hey can also be applied o o he REM
objec s.
4.1. Unambigui y
A equi emen is unambiguous i and only i has only
one possible in e p e a ion [9]. Ob iously, his is a knowl-
edge p ope y and canno be au oma ically e i ied, bu we
can p o ide some heu is ics abou po en ial ambigui ies in
equi emen s in o de o ocus e i ica ion e o on po en-
ially ambiguous equi emen s.
A simple ye powe ul heu is ic o de ec ing ambigui y
(also design dependence, o example) is looking o weak
ph ases indica o s (WPI) in equi emen s desc ip ions, i.e.
"clauses ha a e ap o cause unce ain y and lea e oom o
mul iple in e p e a ions", as desc ibed in [18]. This can be
achie ed by de ining WPI in a ex e nal XML ile like his
(wpi.xml):
<?xml e sion="1.0"?>
<wpis>
<wpi>easy</wpi>
<!-- po en ial ambigui y -->
<wpi>e c</wpi>
<!-- po en ial ambigui y -->
<wpi>no mal</wpi>
<!-- po en ial ambigui y -->
...
<wpi>click</wpi>
<!-- po en ial design dependence -->
<wpi>bu on</wpi>
<!-- po en ial design dependence -->
...
</wpis>
and using he ollowing XSLT code:
<xsl: o -each selec ="// em:useCase">
<xsl: a iable name="uc" selec ="cu en ()"/>
<xsl: o -each selec ="documen (’wpi.xml’)//wpi">
<xsl:i es ="con ains($uc,.)">
Use case <xsl: alue-o selec ="$uc/ em:name"/>
con ains WPI <xsl: alue-o selec ="."/>.
Please, check i .
</xsl:i >
</xsl: o -each>
</xsl: o -each>
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in which e e y use case is checked agains e e y WPI in
wpi.xml. No ice ha he uc a iable is needed since XSLT
does no p o ide any way o accessing mo e han one cu -
en node a di e en le els in nes ed xsl: o -each s uc u es.
Ano he complemen a y app oach o ambigui y heu is-
ics is measu ing how much he cus ome ’s ocabula y is
used in equi emen s desc ip ions. We ag ee wi h Lei e
[12] in he impo ance o unde s anding he language o
he p oblem and in he impo ance o building a glossa y
a he beginning o he elici a ion p ocess. Following Lei e,
wo p inciples should be ollowed: he p inciple o ci cu-
la i y, ( he glossa y mus be as sel –con ained as possible)
and he p inciple o minimal ocabula y ( equi emen s de-
sc ip ions mus use as many glossa y i ems as possible).
Lei e’s p inciples canno gua an ee unambigui y, bu hey
help o build mo e unambiguous, unde s andable, consis-
en , concise, and c oss– e e enced equi emen s [8], and
can be used o measu e he quali y o he glossa y and o
de ec po en ially ambiguous equi emen s.
In he REM XML model, glossa y i ems elemen s a e
mainly composed o em: ex elemen s, so hey can con ain
e e ences o o he REM objec s. In his con ex , XSLT can
be used o measu e glossa y ci cula i y (GLC) and minimal-
i y o ocabula y (MOV). GLC can be measu ed as he a io
be ween he numbe o e e ences o glossa y i ems om
o he glossa y i ems and he numbe o glossa y i ems, as
shown in he ollowing XSLT code:
<xsl: a iable name = "GLC"
selec = "coun (// em:glossa yI em// em: e
[@oid = // em:glossa yI em/@oid]) di
coun (// em:glossa yI em)"
/>
GLC can be used as an indica o o he glossa y qual-
i y. GLC alues unde 1 indica e a low quali y glossa y,
since ha implies ha he e a e glossa y i ems no e e enc-
ing o he glossa y i ems. GLC can also be compu ed o
single glossa y i ems. I seems clea ha glossa y i ems no
e e encing o he glossa y i ems, o e e encing jus a ew
ones (less han 2, o example), should be e i ied o po-
en ial p oblems. The ollowing XSLT code can be used o
ha pu pose:
<xsl: o -each selec ="// em:glossa yI em
[coun (.// em: e [@oid=// em:glossa yI em/@oid]) < 2]"
>
Please, check de ini ion o glossa y i em
<xsl: alue-o selec =" em:name"/>
</xsl: o -each>
MOV can be compu ed, in a simila way o GLC, as he
a io be ween he numbe o e e ences o glossa y i ems in
equi emen s and he numbe o equi emen s. MOV can
be used o pinpoin hose equi emen s ha do no ha e any
e e ence, o jus a ew (less han 4, o example), o any
glossa y i em in hei ex . Since hose equi emen s a e
no using he ocabula y o he cus ome , hey should be
checked o po en ial p oblems o ambigui y o unde s and-
abili y [8]. The same schema used o de ec ing suspicious
glossa y i ems can also be used o de ec ing po en ially am-
biguous equi emen s.
4.2. Comple eness
A equi emen s documen is comple e i i includes [8]:
1. E e y hing ha he so wa e is supposed o do, i.e. all
he equi emen s.
2. Responses o he so wa e o all classes o inpu da a
in all ealizable si ua ions.
3. Page numbe s, igu e and able names and e e ences,
a glossa y, uni s o measu e and e e enced ma e ial.
4. No sec ions ma ked as TBD.
The i s comple eness condi ion mus be checked du ing
equi emen s alida ion ac i i y (see igu e 1) and is he e-
o e ou o he scope o ou app oach.
The second condi ion is a knowledge p ope y e y di -
icul o e i y au oma ically, bu some heu is ics can be
applied when use cases a e used o exp essing unc ional
equi emen s (see sec ion 4.4).
The hi d comple eness condi ion is pa ially sa is ied by
means o he co ec –by–cons uc ion pa adigm o REM:
igu e and able names a e au oma ically gene a ed, e e -
ences a e au oma ically inse ed and upda ed, and he use
can easily c ea e a glossa y.
O ganiza ion, as desc ibed in [8], can also be conside ed
as pa o he hi d comple eness condi ion, so XSLT can
be used o e i y i equi emen s documen s a e o ganized,
i.e. i hey ha e manda o y sec ions in he manda o y o de
wi h manda o y con en . Fo example, i we wan o be su e
abou he exis ence o a sec ion named Awi h a child sec ion
named B, we can apply he ollowing XSLT code:
<xsl:i es ="no (// em:sec ion[ em:name=’A’]/
em:sec ion[ em:name=’B’])">
The e is no A/B sec ion o ganiza ion
</xsl:i >
The ou h condi ion o comple eness can be also e i ied
using XSLT. I we wan o know how many TBD ma ks a e
in a equi emen s documen we can simply use he XPa h
[20] exp ession coun (// em: bd).I wewan obemo ep e-
cise and we wan o know, o example, wha use cases ha e
TBD ma ks inside hei ex and how many TBD ma ks hey
ha e, we can use he ollowing XSLT code:
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<xsl: o -each selec ="// em:useCase[.// em: bd]">
Use case <xsl: alue-o selec =" em:name"/>
has <xsl: alue-o selec ="coun (.// em: bd)"/>
TBD ma ks
</xsl: o -each>
REM au oma ically inse s TBD ma ks in hose equi e-
men s no anno a ed wi h ela i e impo ance o s abili y
[8], so any o hese p ope ies can be checked using a XSLT
code like his:
<xsl: o -each selec ="// em:useCase[./ em:impo ance/ em: bd]">
Use case <xsl: alue-o selec =" em:name"/>
is no anno a ed wi h ela i e impo ance
</xsl: o -each>
4.3. T aceabili y
In [8], a equi emen s documen is said o be aceable i
and only i i is w i en in a manne ha acili a es he e -
e encing o each indi idual equi emen . Since REM au o-
ma ically assigns an unique iden i ie o e e y equi emen ,
his quali y p ope y does no ha e o be e i ied explici ly.
Wha i mus be checked is whe he he o igin o e e y
equi emen is clea o no , i.e. i equi emen s a e aced
in he sense desc ibed in [8]. In he REM model o equi e-
men s, any REM objec can be aced o and om o he REM
objec s and o hei human sou ces and au ho s (see igu e
3). In he REM DTD, aces a e de ined as elemen s wi h
wo equi ed a ibu es o ype IDREF, namely sou ce and
a ge :
<!ELEMENT em: ace EMPTY>
<!ATTLIST em: ace sou ce IDREF #REQUIRED
a ge IDREF #REQUIRED
>
Ha ing said ha , we can use he ollowing XSLT code
o lis all use cases wi h no human sou ces:
<xsl: o -each selec ="// em:useCase[no ( em:sou ces)]">
Use case <xsl: alue-o selec =" em:name"/>
has no de ined sou ces
</xsl: o -each>
and he ollowing one o de ec all use cases no aced o
o he REM objec s:
<xsl: o -each
selec ="// em:useCase[no (// em: ace/@sou ce= @oid)]"
>
Use case <xsl: alue-o selec =" em:name"/>
is no aced o any objec
</xsl: o -each>
REM use s can also use aceabili y ma ices o isual
e i ica ion o aceabili y (see igu e 4). REM use s can
c ea e as many T aceabili yMa ix objec s as hey wish, se-
lec ing he classes o REM objec s hey wan o be shown in
ows in columns.
Figu e 4. REM T aceabili y ma ix example
4.4. Ve i ica ion o use cases
Use cases [15] a e a popula o m o exp essing unc-
ional equi emen s. REM suppo s bo h classic unc ional
equi emen s (i.e. plain ex ) and use cases.
Fo he e i ica ion o use cases, we ha e adop ed a
me ics–based app oach aking he e i ica ion heu is ics
used in he scena io cons uc ion p ocess desc ibed in [11]
as a e e ence. Some me ics based on he REM model o
use cases a e de ined in able 2.
Table 2. REM use case me ics
Me ic Desc ip ion
NOS Numbe o s eps o he use case
NOAS Numbe o ac o ac ion s eps o he use case
NOSS Numbe o sys em ac ion s eps o he use case
NOUS Numbe o use case ac ion s eps o he use case
NOCS Numbe o condi ional s eps
NOE Numbe o excep ions o he use case
NIE Numbe o imes a use case is included o ex ends
o he use cases
So, conside ing he ollowing DTD agmen in which
he REM XML model o use case s eps is desc ibed:
<!ELEMENT em:s ep (
em:numbe , em:condi ion?,
( em:sys emAc ion | em:ac o Ac ion | em:useCaseAc ion ),
em:s epExcep ion*,
em:commen s )>
<!ATTLIST em:s ep oid ID #REQUIRED>
heu is ics based on me ics de ined in able 2 can be applied
using he ollowing XLST code as a pa e n, whe e me ics
alues a e s o ed in auxilia y a iables:
<xsl: o -each selec ="// em:useCase">
<xsl: a iable name="NOS"
selec ="coun ( em:s ep)"/>
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<xsl: a iable name="NOAS"
selec ="coun ( em:s ep[ em:ac o Ac ion])"/>
<xsl: a iable name="NOSS"
selec ="coun ( em:s ep[ em:sys emAc ion])"/>
<xsl: a iable name="NOUS"
selec ="coun ( em:s ep[ em:useCaseAc ion])"/>
<xsl: a iable name="NOCS"
selec ="coun ( em:s ep[ em:condi ion])"/>
<xsl: a iable name="NOE"
selec ="coun ( em:s ep/ em:s epExcep ion)"/>
<xsl: a iable name="NIE" selec =
"coun (// em:useCaseAc ion[@useCase=cu en ()/@oid])"/>
<!-- apply e i ica ion heu is ics he e -->
</xsl: o -each>
The se o e i ica ion–o ien ed, me ics–based heu is-
ics o use cases we ha e de eloped is desc ibed below,
including hei co esponding XLST code ( ha mus be in-
se ed in o he XSLT pa e n). The in e als o usual alues
o me ics ha e been aken a e analyzing 414 use cases de-
eloped by ou s uden s using REM.
4.4.1. Checking he numbe o s eps
Since use cases desc ibe in e ac ions be ween ac o s and he
sys em, a use case should ha e a leas 2 s eps o a minimal
in e ac ion ac o eques –sys em esponse (o he au ho s
like [4] ecommend a alue o NOS in he in e al
[3
;
9]
).
Use cases wi h NOS < 2 should be checked o po en ial
incomple eness. On he o he hand, a high alue o NOS is
an indica o o oo much complexi y o o he lack o s uc-
u e (i.e. includes o ex ends ela ionships) in use cases. The
XSLT code co esponding o his heu is ic is he ollowing:
<xsl:i es ="($NOS < 2) o ($NOS > 9)">
Use case <xsl: alue-o selec =" em:name"/>,
has an unusual numbe o s eps. Please, check i .
</xsl:i >
4.4.2. Checking he a e o di e en ypes o s eps
The h ee ypes o use case s eps in REM, ac o ac ion, sys-
em ac ion and use case ac ion s eps, should no appea wi h
he same equency. Using he same easoning ha in he
p e ious heu is ic, since use cases desc ibe in e ac ions be-
ween ac o s and he sys em, app oxima ely hal he s eps
o a use case should be ac o ac ion s eps and he o he hal
sys em ac ion s eps. On he o he hand, a use case should
no ha e mos o i s s eps being inclusions o ex ensions, i.e.
a high alue o NOUS is a clea indica o o an abusi e use
o use cases ela ionships.
Da a om ou s uden s’use cases poin o he ollowing
usual alues: NOAS/NOS in
[30%
;
70%]
, NOSS/NOS in
[40%
;
80%]
and NOUS/NOS in
[0%
;
25%]
.
As an example, he ollowing XSLT code lis s all use
cases wi h a NOAS/NOS alue ou o usual in e al:
<xsl:i es ="(($NOAS di $NOS) < 0.3) o
(($NOAS di $NOS) > 0.7)">
Use case <xsl: alue-o selec =" em:name"/> has
an unusual a io o ac o s eps. Please check i .
</xsl:i >
4.4.3. Checking he numbe o excep ions
One o he comple eness condi ions enume a ed in sec ion
4.2 is ha a equi emen s documen mus include esponses
o he so wa e o all classes o inpu da a in all ealizable
si ua ions. In he REM model o use cases, sys em beha io
in abno mal si ua ions is desc ibed as excep ions associa ed
o use case s eps. So, i a use case has no excep ions o jus
a ew when compa ed o he numbe o s eps, i is p oba-
bly because only he o dina y sequence o s eps has been
de ined. Thus, his use case should be checked o com-
ple eness. On he con a y, a use case wi h mos o i s s eps
ha ing associa ed excep ions is p obably oo complex o be
unde s ood.
Da a om ou s uden s’poin o usual alues o
NOE/NOS in he in e al
[5%
;
45%]
, so he XSLT code co -
esponding o his heu is ic is he ollowing:
<xsl:i es ="(($NOE di $NOS) < 0.05) o
(($NOE di $NOS) > 0.45)">
Use case <xsl: alue-o selec =" em:name"/> has
an unusual a io o excep ions. Please check i .
</xsl:i >
4.4.4. Checking cycloma ic complexi y
In he same way a use case wi h a high NOE/NOS a e is
p obably oo complex o be unde s ood, a use case wi h
many condi ional s eps is also di icul o unde s and. De-
spi e o he ac ha use cases a e e y di e en om sou ce
code, he heu is ic o keeping cycloma ic complexi y (CC)
low can also be applied o use cases. Cycloma ic complex-
i y o use cases in REM can be compu ed as he numbe o
decision poin s + 1, i.e. he numbe o condi ional s eps +
he numbe o excep ions + 1.
The ollowing XSLT checks cycloma ic complexi y al-
ues o use cases, in which we ha e aken
[1
;
4]
as he usual
in e al o CC as sugges ed by ou s uden s’use cases:
<xsl: a iable name="CC" selec ="$NOCS+$NOE+1"/>
<xsl:i es ="$CC > 4">
Use case <xsl: alue-o selec =" em:name"/>
has a unusual alue o cycloma ic complexi y.
Please, check i .
</xsl:i >
4.4.5. Checking abs ac use cases
Abs ac use cases a e hose use cases ha can only be pe -
o med om o he use cases and he e o e canno be ig-
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ge ed by any e en . The usual mo i a ion o he c ea ion
o abs ac use cases is a oiding he epe i ion o common
sequences o s eps in o he use cases. I an abs ac use case
is nei he included om o he use cases no i ex ends o he
use cases is clea ly useless and should be dele ed om he
speci ica ion. I i is used o only one use case, i should
be me ged in o he calling use case. The XSLT code co e-
sponding o his heu is ic is he ollowing:
<xsl:i es =" em:isAbs ac and $NIE < 2">
Abs ac use case <xsl: alue-o selec =" em:name"/>
is ha dly used. Please, check i .
</xsl:i >
4.4.6. Checking ac o pa icipa ion
Ano he e i ica ion heu is ic included in [11] is checking
i e e y ac o pa icipa e in a leas one use case. All s ep
ac ion elemen s in he REM DTD ha e an ac o a ibu e o
ype IDREF, so he ollowing XSLT code can be used o
checking i an ac o pa icipa es a leas in one use case:
<xsl: o -each selec ="// em:ac o
[no (// em:ac o Ac ion/@ac o = @oid)]">
Ac o <xsl: alue-o selec =" em:name"/>
does no pa icipa e in any use case.
Please, check i .
</xsl: o -each>
5. Rela ed wo k
Some o he esul s o he ESPRIT p ojec CREWS, es-
pecially s yle and con en guidelines o ex ual speci ica-
ion o use cases [17] ha e in luenced ou wo k. Thei ap-
p oach, implemen ed in he CREWS-SAVRE and L’Ec i oi e
ools, combines na u al language p ocessing (NLP) ech-
niques and linguis ic pa e ns, guiding he cons uc ion o
use cases and p o iding ambigui y de ec ion mechanisms
which a e much mo e powe ul han ou s.
We use linguis ic pa e ns ex ensi ely [6] and ou UML
model o equi emen s is pa ially based on CREWS esul s,
bu we ha e no adop ed an NLP–based app oach o e i i-
ca ion because one o ou goals was o le REM use s w i e
hei own e i ica ion p og ams (i.e. XSLT s yleshee s). Us-
inganNLP–based e i ica ion app oach would ha e made
his goal e y di icul o sa is y because o hei complexi y.
We a e cu en ly conduc ing expe imen s wi h ou s uden s
in o de o know i ou simple app oach yields compa able
esul s o he ones desc ibed in [2].
The Au oma ed Requi emen Measu emen (ARM) ool
[18], is a simple ye powe ul, no NLP–based equi emen s
e i ica ion ool ha scans equi emen s documen s o spe-
ci ic wo ds and ph ases ha a e conside ed indica o s o he
quali y o equi emen s. As shown in sec ion 4.1, REM can
pe o m he same ype o analysis using XSLT and apply a
wide se o e i ica ion–o ien ed heu is ics.
Schema on [10] is an XML–based language o speci-
ying asse ions on XPa h exp essions in XML documen s.
A Schema on documen mus be ans o med in o a XSLT
s yleshee using he Schema on XSLT s yleshee and hen
applying he esul ing s yleshee o he XML documen
being analyzed. Ou app oach and Schema on elies on
XPa h exp essions, bu ou s needs only one XSLT ans o -
ma ion and p o ides g ea e lexibili y o p esen ing esul s
o use s and o compu ing equi emen s–o ien ed me ics.
The xlinki language [13] is an XML–based language o
speci ying consis ency ules be ween XML documen s us-
ing a es ic ed se o i s o de logic and XPa h exp es-
sions. Mos XSLT e i ica ion code p esen ed in his pape
can be exp essed in xlinki . Fo example he XSLT code in
sec ion 4.3 o de ec ing use cases no aced o o he REM
objec s can be ansla ed in o he ollowing xlinki code,
which iden i ies all use cases no aced o any objec as in-
consis en links:
<globalse id="$useCases" xpa h="// em:useCase"/>
<globalse id="$ aces" xpa h="// em: ace"/>
<consis ency ule id="beT aced">
<desc ip ion>
E e y use case mus be aced o some objec ,
i.e. mus be he sou ce o some ace
</desc ip ion>
< o all a ="uc" in="$useCases">
<exis s a =" " in="$ aces">
<equal op1="$uc/@oid" op2="$ /@sou ce"/>
</exis s>
</ o all>
</consis ency ule>
T ansla ing o he XSLT agmen s in o xlinki equi es
he use o he XPa h unc ion ue (xlinki only allows
equali y and inequali y exp essions on XPa h exp essions
as p edica es), and he expansion o a iable exp essions
(xlinki does no allow he decla a ion o local a iables in-
side o all o exis s elemen s). Fo example, he xlinki code
co esponding o he Checking he numbe o s eps heu is ic
is he ollowing:
<globalse id="$useCases" xpa h="// em:useCase"/>
<consis ency ule id="checkingNOS">
<desc ip ion>
E e y use case should ha e 2<=NOS<=9
</desc ip ion>
< o all a ="uc" in="$useCases">
<equal op1="(coun ($uc/ em:s ep) >= 2) and
(coun ($uc/ em:s ep) <= 9)"
op2=" ue()"
/>
</ o all>
</consis ency ule>
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REM e i ica ion s yleshee s mus be XSLT in o de o
be p ocessed by he REM use in e ace and hey mus be
as e icien as possible o as isual eedback o he use .
xlinki ules mus be p ocessed by a Ja a p og am so ha
makes i incompa ible wi h REM. On he o he hand, xlinki
p esen s esul s as xlinks, some hing ha is no cu en ly
suppo ed by mos web b owse s.
DOORS, a comme cial RE ool wi h much mo e ea u es
han REM, includes a C++–like sc ip ing language called
DXL [1]. Using DXL, i is possible o implemen some o
he heu is ics desc ibed in his pape , bu he DOORS use
mus de ine all necessa y a ibu es and ypes o objec s o
ha e a equi emen s model simila o ou s in DOORS. Apa
om he ac ha ou app oach is based on s anda d lan-
guages and no in a p op ie a y one like DXL, he e sa il-
i y o e ed by XML and XSLT ( o epo gene a ion, o
example) is a om he o e ed by DXL (unless XML is
gene a ed om DXL).
6. Conclusions and u u e wo k
In his pape we ha e p esen ed an au oma ed, ligh –
weigh , XSLT–based app oach o he e i ica ion o e-
qui emen s which is in eg a ed in he REM RE ool. Ou ap-
p oach is based on a open echnology like XML and o e s
all he lexibili y o XSLT. In ac , i equi emen s a e ep e-
sen ed in XML no using he REM DTD, many o he XSLT–
based e i ica ion–o ien ed heu is ics p esen ed in his pa-
pe should be easily adap able.
Ou u u e wo k is ocused on iden i ying accu a e in-
e al alues o hose me ics–based e i ica ion heu is ics
(glossa y–based and use case heu is ics mainly). We a e
cu en ly conduc ing an expe imen wi h ou s uden s a he
Uni e si y o Se ille wi h wo main goals in mind. The
i s goal is de e mining in e al alues by applying da a
mining echniques o ou s uden s’RE p ojec s, hus iden-
i ying co ela ions be ween de ec s and me ic alues. The
second goal is o know whe he ou app oach imp o es e-
qui emen s e i ica ion o no , i.e. i mo e de ec s in e-
qui emen s a e de ec ed when equi emen s e i ica ion is
suppo ed by ou XSLT–based heu is ics.
O he lines o u u e wo k a e he de eloping o XSLT
s yleshee s o compu ing use case poin s [19] and o
g aphical isualiza ion o e i ica ion–o ien ed me ics in
web b owse s.
Acknowledgmen s
We wish o hank Julio Lei e o his commen s and sug-
ges ions on an ea ly e sion o his pape .
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