Supporting Requirements Verification Using XSLT

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  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]. P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 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, P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE 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> P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE 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: P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE <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)"/> P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE <xsl: a iable name="NOAS" selec ="coun ( em:s ep[ em:ac o Ac ion])"/> <xsl: a iable name="NOSS" selec ="coun ( em:s ep[ em:sys emAc ion])"/> <xsl: a iable name="NOUS" selec ="coun ( em:s ep[ em:useCaseAc ion])"/> <xsl: a iable name="NOCS" selec ="coun ( em:s ep[ em:condi ion])"/> <xsl: a iable name="NOE" selec ="coun ( em:s ep/ em:s epExcep ion)"/> <xsl: a iable name="NIE" selec = "coun (// em:useCaseAc ion[@useCase=cu en ()/@oid])"/> <!-- apply e i ica ion heu is ics he e --> </xsl: o -each> The se o e i ica ion–o ien ed, me ics–based heu is- ics o use cases we ha e de eloped is desc ibed below, including hei co esponding XLST code ( ha mus be in- se ed in o he XSLT pa e n). The in e als o usual alues o me ics ha e been aken a e analyzing 414 use cases de- eloped by ou s uden s using REM. 4.4.1. Checking he numbe o s eps Since use cases desc ibe in e ac ions be ween ac o s and he sys em, a use case should ha e a leas 2 s eps o a minimal in e ac ion ac o eques –sys em esponse (o he au ho s like [4] ecommend a alue o NOS in he in e al [3 ; 9] ). Use cases wi h NOS < 2 should be checked o po en ial incomple eness. On he o he hand, a high alue o NOS is an indica o o oo much complexi y o o he lack o s uc- u e (i.e. includes o ex ends ela ionships) in use cases. The XSLT code co esponding o his heu is ic is he ollowing: <xsl:i es ="($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- P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE 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> P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE 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 . Re e ences [1] I. Alexande . Ge ing S a ed wi h DXL, he DOORS eX en- sion Language. Technical epo , Telelogic Inno a e, 2001. [2] C. Ben Achou , C. Rolland, N. A. M. Maiden, and C. Sou- eye . Guiding Use Case Au ho ing: Resul s o an Empi ical S udy. In ISRE’99 P oceedings, 1999. [3] G. Booch, J. Rumbaugh, and I. Jacobson. The Uni ied Mod- eling Language Use Guide. Addison–Wesley, 1999. [4] A. Cockbu n. W i ing E ec i e Use Cases. Addison– Wesley, 2001. [5] A. Du án. A Me hodological F amewo k o Requi emen s Enginee ing o In o ma ion Sys ems (in Spanish).PhD he- sis, Uni e si y o Se ille, 2000. [6] A. Du án, B. Be ná dez, A. Ruiz, and M. To o. A Requi e- men s Elici a ion App oach Based in Templa es and Pa - e ns. In WER’99 P oceedings, Buenos Ai es, 1999. [7] A. Du án, A. Ruiz, B. Be ná dez, and M. To o. Ve i ying So wa e Requi emen s wi h XSLT. ACM So wa e Engi- nee ing No es, 27(1), 2002. [8] A. Da is e al. Iden i ying and Measu ing Quali y in a So - wa e Requi emen s Speci ica ion. In P oceedings o he 1s In e na ional So wa e Me ics Symposium, pages 141–152, 1993. [9] IEEE. Recommended P ac ice o So wa e Requi emen s Speci ica ions. IEEE/ANSI S anda d 830–1998. [10] R. Jelli e. The Schema on Asse ion Language 1.5. Tech- nical epo , Academia Sinica Compu ing Cen e, 2001. [11] J. C. S. P. Lei e, H. Hadad, J. Doo n, and G. Kaplan. A Scena io Cons uc ion P ocess. Requi emen s Enginee ing Jou nal, 5(1), 2000. [12] J. C. S. P. Lei e, G. Rossi, F. Balague , V. Maio ana, G. Ka- plan, G. Hadad, and A. Oli e os. Enhancing a Requi e- men s Baseline wi h Scena ios. In P oceedings o he 3 d IEEE In e na ional Symposium on Requi emen s Enginee - ing (RE’97), 1997. [13] C. Nen wich, W. Emme ich, and A. Finkesl ein. S a ic con- sis ency checking o dis ibu ed speci ica ions. In P oceed- ings o Au oma ed So wa e Enginee ing, 2001. [14] OMG. XML Me ada a In e change (XMI) Speci ica ion 1.1. Technical epo , No embe 2000. [15] OMG. Uni ied Modeling Language, 1.4. Technical epo , Sep embe 2001. [16] S. Robe son and J. Robe son. Mas e ing he Requi emen P ocess. Addison–Wesley, 1999. [17] C. Rolland and C. B. Achou . Guiding he Cons uc ion o Tex ual Use Case Speci ica ions. Da a & Knowledge Engi- nee ing Jou nal, 25(1–2), 1998. [18] L. Rosenbe g, T. F. Hamme , and L. L. Hu man. Requi e- men s, Tes ing and Me ics. In 15 h Annual Paci icNo h- wes So wa e Quali y Con e ence, U ah, 1998. [19] G. Schneide and J. P. Win e s. Applying Use Cases: a P ac- ical Guide. Addison–Wesley, 1998. [20] W3C. XML Pa h Language (XPa h) 1.0. W3C Recommen- da ion, No embe 1999. [21] W3C. XSL T ans o ma ions (XSLT) 1.0. W3C Recommen- da ion, No embe 1999. [22] W3C. Ex ensible Ma kup Language (XML) 1.0 (Second Edi ion). W3C Recommenda ion, Oc obe 2000. P oceedings o he IEEE Join In e na ional Con e ence on Requi emen s Enginee ing (RE’02) 1090-705X/02 $17.00 © 2002 IEEE