Business Systems Analysis with Ontologies

Transcription

1 Businss Systms Analysis with Ontologis Ptr Grn Univrsity of Qunsland, Australia Michal Rosmann Qunsland Univrsity of Tchnology, Australia IDEA GROUP PUBLISHING Hrshy London Mlbourn Singapor

2 Acquisitions Editor: Dvlopmnt Editor: Snior Managing Editor: Managing Editor: Copy Editor: Typsttr: Covr Dsign: Printd at: Rné Davis Kristin Roth Amanda Appicllo Jnnifr Nidig Dawn Brooks Kristin Roth Lisa Toshff Yurchak Printing Inc. Publishd in th Unitd Stats of Amrica by Ida Group Publishing (an imprint of Ida Group Inc.) 701 E. Chocolat Avnu Hrshy PA Tl: Fax: Wb sit: and in th Unitd Kingdom by Ida Group Publishing (an imprint of Ida Group Inc.) 3 Hnritta Strt Covnt Gardn London WC2E 8LU Tl: Fax: Wb sit: Copyright 2005 by Ida Group Inc. All rights rsrvd. No part of this book may b rproducd, stord or distributd in any form or by any mans, lctronic or mchanical, including photocopying, without writtn prmission from th publishr. Product or company nams usd in this book ar for idntification purposs only. Inclusion of th nams of th products or companis dos not indicat a claim of ownrship by IGI of th tradmark or rgistrd tradmark. Library of Congrss Cataloging-in-Publication Data Businss systms analysis with ontologis / Ptr Grn and Michal Rosmann, ditors. p. cm. Summary: "This book shows systms analysts and businss analysts how ontological thinking can hlp thm clarify rquirmnts analysis tasks in businss systms"--providd by publishr. Includs bibliographical rfrncs and indx. ISBN (h/c) -- ISBN (s/c) -- ISBN (book) 1. Industrial managmnt--data procssing. 2. Information rsourcs managmnt. 3. Ontology. I. Grn, Ptr, II. Rosmann, Michal, HD30.2.B '.001--dc British Cataloguing in Publication Data A Cataloguing in Publication rcord for this book is availabl from th British Library. All work contributd to this book is nw, prviously-unpublishd matrial. Th viws xprssd in this book ar thos of th authors, but not ncssarily of th publishr.

3 130 Rinhartz-Brgr & Dori Chaptr VI A Rflctiv Mta-Modl of Objct-Procss Mthodology: Th Systm Modling Building Blocks Iris Rinhartz-Brgr, Univrsity of Haifa, Isral Dov Dori, Tchnion, Isral Institut of Tchnology, Isral Abstract In this chaptr, w introduc a highly xprssiv, slf-containd rflctiv mta-modl of objct-procss mthodology (OPM). OPM nabls univrsal systm modling basd on th notions of procsss that transform objcts. Extnding th objct-orintd approach, which viws procsss as rsidnts of objcts, OPM provids for th xistnc of stand-alon procsss that can rprsnt transformations in complx systms such as businsss, aircrafts or organisms. A systm modling and dvlopmnt mthodology,

4 A Rflctiv Mta-Modl of Objct-Procss Mthodology 131 which is a combination of a languag for xprssing th univrsal (or domain) ontology and an approach for dvloping systms that uss this languag, can b xprssd in OPM using objcts, procsss and links among thm. Through th rflctiv OPM mta-modl, w dmonstrat th xprssiv powr of OPM and its applicability as a univrsal tool for architcting systms that involv structur and dynamics in a highly, intrtwind mannr. Introduction A systm modling and dvlopmnt mthodology is a combination of a languag for xprssing th univrsal or domain ontology and an approach or a protocol for dvloping systms that maks ffctiv us of this languag. Mta-modling, th procss of modling a mthodology, nabls building, undrstanding, comparing, and valuating mthodologis. Th mta-modling procss producs a mta-modl, that is, a modl of th mthodology (Mta- Modl, 2003). W rfr to a mthodology that can modl itslf as a rflctiv mthodology, and to mta-modling of a rflctiv mthodology as rflctiv mta-modling. In othr words, a rflctiv mta-modl is dfind xclusivly in trms of th modld mthodology. A rflctiv mthodology is spcially powrful sinc it is slf-containd, so it dos not rquir auxiliary mans or xtrnal tools to modl itslf. Objct-procss mthodology (OPM), which is a holistic systm modling, dvlopmnt and volution approach that combins objct-orintd notations with procss-orintd concpts, is a rflctiv mthodology. As notd, mta-modls hav bcom important mans for comparing and valuating mthodologis and thir supporting CASE tools. By and larg, mtamodls ar structur- or objct-orintd, and hnc prtain only to th static lmnts and rlations of th mthodology. Thy thrfor do not includ th procdural parts of th mthodology (also known as th softwar procss ). Rathr, ths ar usually dscribd loosly and informally in som natural languag, most oftn English. Th main rason for this omission of th mthodology s procss part is th lack of xprssiv powr of th mthodology to samlssly and straightforwardly dscrib not only objcts and structur but also procsss and bhavior. OPM ovrcoms this shortcoming by trating objcts and procsss as two qually important ntitis rathr than viwing objct classs ncssarily as supriors to and ownrs of procsss. Through th bimodal OPM modl prsntation of objct-procss diagrams (OPDs) and objct-procss languag (OPL) sntncs, this chaptr prsnts th rflctiv mta-modl of th

5 132 Rinhartz-Brgr & Dori languag and notation parts of OPM, namly its smantics and syntax. Th othr part of th rflctiv OPM mta-modl, which spcifis OPM-basd systm dvlopmnt and volution procsss, can b found in Dori (2002, pp ) and Dori and Rinhartz-Brgr (2003). A major significanc of this work is that it lays out a comprhnsiv, gnric, and formal dfinition of OPM that nabls domain-indpndnt modling of complx systms, in which structur and bhavior ar intrtwind and hard to sparat. Indd, ral-lif systms of intrst can almost always b charactrizd as such. Th chaptr is structurd as follows. First, th main mta-modling concpts ar dfind and xisting mta-modling approachs ar rviwd. Thn, th main concpts of OPM ar introducd and xmplifid through a businss ntrpris modl that handls customr ordrs and rtailr rqusts. Th main part of th chaptr is th OPM rflctiv mta-modl, including all its lmnts, ntitis, and structural, procdural, and vnt links. Finally, th contribution of OPM as a univrsal businss modling mthodology is summarizd, mphasizing its rol in dfining nw mthodologis. Rflctiv Mthodologis and Rflctiv Mta-Modling Systm analysis and dsign activitis can b dividd into thr typs with incrasing abstraction lvls: ral world, modl, and mta-modl (Van Gigch, 1991). Th ral world is what systm analysts prciv as rality or what systm architcts wish to crat as rality. A modl is an abstraction of this prcivd or contmplatd rality that nabls its xprssion using som approach, languag, or mthodology. A mta-modl is a modl of a modl, or, mor accuratly, a modl of th modling mthodology (Mta-Modl, 2003). Mtamodls hlp undrstand th dp smantics of a mthodology as wll as rlationships among concpts in diffrnt languags or mthods. Thy can thrfor srv as dvics for mthods dvlopmnt, also rfrrd to as mthods nginring (Nusibh, Finklstin, & Kramr, 1996; Rossi, Tolvann, Ramsh, Lyytinn, & Kaipala, 2000), and as concptual schmas for rpositoris of softwar nginring and CASE tools. Mta-modling is th procss that crats mta-modls. Th lvl of abstraction at which mta-modling is carrid out is highr than th lvl at which modling is normally don for th purpos of gnrating a modl of a systm (Hndrson- Sllrs & Bulthuis, 1998).

6 A Rflctiv Mta-Modl of Objct-Procss Mthodology 133 Th prolifration of objct-orintd mthods has givn ris to a spcial typ of mta-modling rflctiv mta-modling, that is, modling a mthodology using its own mans alon. Whil mta-modling is a formal dfinition of th mthodology, rflctiv mta-modling can srv as a common way to chck and dmonstrat th mthodology s xprssiv powr. Existing objct-orintd languags, notably th standard unifid modling languag (UML), hav partial rflctiv mta-modls. Th rflctiv UML mtamodl in Objct Managmnt Group (2001), for xampl, includs class diagrams; OCL (objct constraint languag) (Warmr & Klpp, 1999) constraints, which ar addd on top of th UML graphics as a txtual mans to xprss constraints; and natural languag xplanations for dscribing th main lmnts in UML and th static rlations among thm. This mta-modl is incomplt in mor than on way. First, UML is only a notation and not a mthodology, so only th languag lmnts ar mta-modld, but not any (objct-orintd or othr) dvlopmnt procss. Scond, class diagrams ar usd to modl all 10 UML viws (diagram typs) and th mta-modl dos not nforc complt consistncy rquirmnts among th various viws of a UML systm modl. Third, most of th mta-modl (structural) constraints ar xprssd in OCL, which is a programming-languag-lik add-on to UML. Th mta objct facility (MOF) (Objct Managmnt Group, 2003) is a standard mtadata architctur whos main thm is xtnsibility and support of mtadata. MOF dfins four layrs of mtadata: information (i.., ral world concpts, labld M0), modl (M1), mta-modl (M2), and mta-mta-modl (M3). Th mta-mta-modl layr dscribs th structur and smantics of mta-mtadata. In othr words, it is an abstract languag for dfining diffrnt kinds of mtadata (.g., mta-classs and mta-attributs). Th mta modling facility (MMF) (Clark, Evans, & Knt, 2002) provids a modular and xtnsibl mthod for dfining and using modling languags. It compriss a static, objct-orintd languag (MML) to writ languag dfinitions, a tool (MMT) to intrprt thos dfinitions, and a mthod (MMM), which provids guidlins and pattrns ncodd as packags that can b spcializd to particular languag dfinitions. MOF and MMF hav bn applid to mta-modl UML. Sinc both ar objctorintd, thy mphasiz UML lmnts, whil th procdural aspcts ar supprssd. Sinc OPM combins th objct- and procss-orintd approachs in a singl framwork, it can spcify systm structur and dynamics in a balancd way. In particular, mta-modls xprssd in OPM captur both th languag and th systm dvlopmnt approach parts of th modld mthodology.

7 134 Rinhartz-Brgr & Dori Objct-Procss Mthodology in a Nutshll Objct-procss mthodology (OPM) (Dori, 2002) is a holistic approach to th modling, study, dvlopmnt, and volution of systms. Structur and bhavior coxist in th sam OPM modl to nhanc th comprhnsion of th systm as a whol. Contrary to UML with its tn diagram typs, OPM shows th systm s structur and bhavior in th sam and singl diagram typ, nabling dirct xprssion of rlations, intractions, and ffcts. This trait rinforcs th usrs ability to construct, grasp, and comprhnd th systm as a whol and at any lvl of dtail. Morovr, Soffr, Golany, Dori, and Wand (2001) concludd that OPM is ontologically complt according to th Bung-Wand-Wbr (BWW) valuation framwork (Wand & Wbr, 1993). Th BWW framwork aims to b a thortical foundation for undrstanding th modling of information systms. Any modling languag (or grammar) must b abl to rprsnt all things in th ral world that might b of intrst to usrs of information systms, othrwis, th rsultant modl is incomplt (Rosmann & Grn, 2002). Hnc, OPM compltnss according to th BWW framwork is indicativ of OPM s xprssiv powr. Appndix A lists th ontological constructs of information systms, thir BWW xplanations, and thir OPM rprsntation as indictd in Soffr, Golany, Dori, and Wand (2001). Du to its structur-bhavior intgration, OPM provids a solid basis for modling complx systms. Indd, OPM has bn xtndd to support th modling of common typs of systms, including ral-tim systms (Plg & Dori, 1999), ERP (Soffr, Golany, & Dori, 2003), and Wb applications (Rinhartz- Brgr, Dori, & Katz, 2002a, 2002b). Thr indpndnt xprimnts showd that OPM is mor comprhnsibl than objct-orintd tchniqus in modling th dynamic and ractiv aspcts of ral tim systms (Plg & Dori, 2000), Wb applications (Rinhartz-Brgr & Dori, 2005), and discrt vnt simulation systms. OPM Concpts Th lmnts of OPM ontology ar ntitis and links. Entitis gnraliz things and stats. A thing is a gnralization of an objct and a procss th two basic building blocks of any OPM-basd systm modl. At any point in tim, ach objct is at som stat, and objct stats ar changd through th occurrnc of procsss. Analogously, links can also b structural or procdural. Structural links xprss static, structural rlations btwn pairs of objcts or procsss. Ths rlations hold for th systm rgardlss of th tim dimnsion. Aggrga-

8 A Rflctiv Mta-Modl of Objct-Procss Mthodology 135 tion, gnralization, charactrization, and instantiation ar th four fundamntal structural rlations. In addition, gnral structural rlations can tak on any smantics, which is xprssd txtually by thir usr-dfind tags. Th bhavior of a systm is manifstd in thr major ways: 1) procsss can transform (gnrat, consum, or chang) things, 2) things can nabl procsss without bing transformd by thm, and 3) things can triggr vnts that (at last potntially, if som conditions ar mt) invok procsss. Accordingly, a procdural link can b a transformation link, an nabling link, or an vnt link. Th complxity of an OPM modl is controlld through thr scaling (rfinmnt/abstraction) procsss: in-zooming/out-zooming, in which th ntity bing rfind is shown nclosing its constitunt lmnts; unfolding/folding, in which th ntity bing rfind is shown as th root of a dirctd graph; and stat xprssing/supprssing, which allows for showing or hiding th possibl stats of an objct. Ths mchanisms nabl OPM to rcursivly spcify and rfin th systm undr dvlopmnt to any dsird lvl of dtail without losing lgibility and comprhnsion of th complt systm. Each tim a diagram is about to gt too cluttrd, a nw diagram can b spawnd. Th nw diagram is linkd to and laborats upon th ancstor diagram. Th Bimodal Graphic-Txt Rprsntation of OPM Two smantically quivalnt modalitis, on graphic and th othr txtual, jointly xprss th sam OPM modl. A st of intr-rlatd objct-procss diagrams (OPDs), constitut th graphical, visual OPM formalism. Each OPM lmnt is dnotd in an OPD by a ddicatd symbol, and th OPD syntax spcifis corrct and consistnt ways by which ntitis can b connctd via structural and procdural links. Th objct-procss languag (OPL), prcisly dfind by a grammar, is th txtual countrpart modality of th graphical OPD st. OPL is a dual-purpos languag, orintd towards humans as wll as machins. Catring to human nds, OPL is dsignd as a constraind subst of English, which srvs domain xprts and systm architcts. All th stakholdrs can us th OPL spcification along with th corrsponding OPDs to jointly ngag in analyzing and dsigning a systm. Evry OPD construct is xprssd by a smantically quivalnt OPL sntnc or phras. Dsignd also for machin intrprtation through a wll-dfind st of production ruls, OPL provids a solid basis for automating th gnration of th dsignd application. According to Mayr s cognitiv thory (2001), this dual rprsntation of OPM incrass th procssing capability of humans. Morovr, OPDs constitut a complt and consistnt visual formalism that gos hand in hand with th OPL in th following maning: Anything that is xprssd graphically by an OPD is also xprssd txtually in th corrsponding OPL paragraph, and vic vrsa.

9 136 Rinhartz-Brgr & Dori OPCAT (Dori, Rinhartz-Brgr, & Sturm, 2003), a Java-basd objct-procss CASE tool, automatically translats ach OPD into its quivalnt OPL paragraph (collction of OPL sntncs) and vic vrsa. OPM Concpts Dmonstratd by an Invntory Systm Modl Bfor prsnting th OPM rflctiv mta-modl, in this sction w xplain and dmonstrat OPM concpts through an OPM modl of a simpl businss ntrpris invntory systm that handls ordrs. This ntrpris can gt rqusts for products from individual customrs or from rtailrs. Th OPM modl of this ntrpris, which includs information modling as wll as businss procss spcification, is prsntd in Figurs 1-7 using both OPDs and thir corrsponding OPL paragraphs. This dual rprsntation incrass th modl clarity and accssibility, as radrs who ar familiar with OPM and its graphical notation can us th OPDs, whil radrs who ar nw with OPM will probably prfr to start with th OPL paragraphs. Sinc th graphical and txtual notations of OPM ar quivalnt, and, from a cognitiv viwpoint, complmntary, th radr can choos th modality (txt or graphics) with which h/sh is most comfortabl and switch btwn th two at will. Furthrmor, th OPL paragraphs ar slfdocumntd and hnc nd no furthr xplanations. OPM Elmnts As notd, OPM consists of two typs of lmnts: ntitis and links. Entitis ar classifid into things and stats. A thing is a gnralization of an objct and a procss. Objcts ar ntitis that xist, whil procsss ar ntitis that transform things by gnrating, consuming, or affcting thm. A stat is a situation at which an objct xists. Thrfor, a stat is not a stand-alon ntity, but rathr an ntity that is ownd by an objct. At any givn point in tim, th stat-owning objct is at on of its stats. Th status of an objct, that is, th currnt stat of th objct, is changd solly through an occurrnc of a procss. Objcts and procsss ar rspctivly dnotd in an OPD by rctangls (as in class diagrams in UML and arlir notations) and llipss (as in data-flow diagrams). Following Statcharts (Harl, 1987) notation, th OPD symbol of a stat is a roundd cornr rctangl within th rctangl of its owning objct. In Figur 1, for xampl, Ordr, Rcipt, Product Catalog, Customr, and Rtailr ar objcts, whil Ordring is a procss. In Figur 2, cratd, paid, supplid, and compltd ar stats of th Ordr Status attribut.

10 A Rflctiv Mta-Modl of Objct-Procss Mthodology 137 Figur 1. Top lvl, Systm Diagram (SD) of th ordring systm Product Catalog is nvironmntal. Rcipt is physical. Ordring lasts 1 minut to 5 minuts. Ordring rquirs 2 Product Catalogs. Ordring yilds Ordr and Rcipt. Customr is nvironmntal and physical. Rtailr is nvironmntal and physical. Eithr Rtailr or Customr handls Ordring. Figur 2. SD1, in which Ordr is structurally unfoldd Ordr xhibits Ordr Numbr, Ordr Status, Ordr Dat, and Ordr Pric, as wll as Printing. Ordr Numbr is of typ intgr. Ordr Status can b cratd, which is th dfault, paid, supplid, or compltd. Cratd is initial. Cratd lasts 2 sconds to 30 sconds. Paid can b advanc paid, which is th dfault, or compltly paid. Advanc paid is initial. Compltd is final. Ordr Dat is of typ dat. Ordr Pric is of typ float. Ordr consists of optional Ordr Lins. Ordr Lin xhibits Product ID and Quantity. Ordr is placd by ithr Prson or Coopration. Supplid Ordr is an Ordr, th Ordr Status of which is supplid. Ordr 123 is an instanc of Ordr, th Ordr Status of which is paid. A link is an lmnt that conncts two ntitis to rprsnt som smantic rlation btwn thm. Links can b structural or procdural. A structural link is a binary rlation btwn two ntitis, which spcifis a structural aspct of th modld systm, such as an aggrgation-participation (whol-part) or a gnralization-spcialization rlation. A procdural link conncts an ntity with a procss to dnot a dynamic, bhavioral flow of information, matrial, nrgy, or control. An vnt link is a spcialization of a procdural link which modls a significant happning in th systm that taks plac during a particular momnt and might triggr a procss if prconditions ar mt.

11 138 Rinhartz-Brgr & Dori Links ar dnotd in an OPD by lins with diffrnt typs of arrowhads or triangls, as summarizd in Appndix B. In Figur 1, for xampl, Ordring, which is triggrd (activatd) by ithr Customr or Rtailr, uss Product Catalog as an input, and crats Ordr and Rcipt as outputs. Any OPM lmnt can b ithr systmic or nvironmntal. A systmic lmnt is intrnal to th systm and has to b compltly spcifid, whil an nvironmntal lmnt is xtrnal to th systm modl and may thrfor b spcifid only partially. Th OPD symbol of an nvironmntal lmnt diffrs from its systmic countrpart in that its bordrlin is dashd. Th Product Catalog in Figur 1, for xampl, is an nvironmntal objct; it is xtrnal to th systm but should b usd as an unchangabl input for th Ordring procss. In an orthogonal fashion, an OPM lmnt can also b ithr physical or informatical. A physical lmnt is tangibl in th broad sns, whil an informatical lmnt rlats to information. A physical ntity is symbolizd in an OPD as a shadowd closd shap rctangl, llips, or roundd cornr rctangl for a physical objct, a physical procss, or a physical stat, rspctivly. Th Rcipt in Figur 1, rsulting from th Ordring procss, is a systmic and physical objct, whil th Customr and th Rtailr ar nvironmntal and physical objcts. OPM Things As notd, a thing is a gnralization of an objct and a procss. A thing can b simpl or complx. A thing is simpl if it has no parts, faturs (attributs or oprations), or spcializations, and is complx othrwis. An objct is a thing that xists, at last potntially, and rprsnts a class of instancs that hav th sam structur and can xhibit th sam bhavior. Th Ordr in Figur 2, for xampl, is a complx objct which xhibits four simpl attributs (ach of which is an objct in its own right): Ordr Numbr, which is of typ intgr, Ordr Status, which is of an numration typ, Ordr Dat, which is of typ dat, and Ordr Pric, which is of typ float. A procss is a class of occurrncs (or instancs) of a bhavior pattrn, which transforms at last on thing. Transformation can b cration, consumption, or ffct (stat chang) of a thing (usually an objct). To carry out th transformation, th procss may nd to b nabld by on or mor things of diffrnt typs of classs, which ar considrd instrumnts (nablrs) for that procss. An instrumnt is a non-human objct that is not transformd by th procss it nabls. Analogous to an objct instanc, a procss instanc is an occurrnc (on-tim xcution) of th spcific procss. Th xcution tim of a procss can b

12 A Rflctiv Mta-Modl of Objct-Procss Mthodology 139 Figur 3. SD2, in which Ordring is in-zoomd Ordr xhibits Ordr Status. Ordr Status can b paid, supplid, or compltd. Paid is initial. Compltd is final. Product Catalog is nvironmntal. Rcipt is physical. Ordring lasts 1 minut to 5 minuts. Ordring rquirs 2 Product Catalog. Ordring zooms into Ordr Cration, Ordr Vrification, Rtailr Ordr Handling, Customr Ordr Handling, and Rcipt Gnrating, as wll as Product Rqust and Ordr Typ. Ordr Typ can b customr or rtailr. Ordr Cration yilds Product Rqust. Following path individual, Ordr Cration yilds customr Ordr Typ. Following path rtail, Ordr Cration yilds rtailr Ordr Typ. Ordr Vrification consums Product Rqust. Ordr Vrification yilds Ordr. Rtailr Ordr Handling occurs if Ordr Typ is rtailr. Rtailr Ordr Handling affcts Ordr. Customr Ordr Handling occurs if Ordr Typ is customr. Customr Ordr Handling affcts Ordr. Rcipt Gnrating changs Ordr Status from ithr supplid or paid to compltd. Rcipt Gnrating yilds Rcipt. Customr is nvironmntal and physical. Following path individual, Customr handls Ordr Cration. Rtailr is nvironmntal and physical. Following path rtail, Rtailr handls Ordr Cration. constraind by minimal and maximal limits, implying that any procss xcution can only tak a tim intrval that falls within ths tim limits. Th tim limits appar in th OPD as (minimal tim constraint, maximal tim constraint) within th llips rprsnting th procss. For xampl, th spcification of th minimal and maximal tim limits of th Ordring procss in Figur 1 and Figur 3 implis that it must tak at last 1 minut and at most 5 minuts. Th corrsponding OPL sntnc is Ordring lasts 1 minut to 5 minuts. Following th UML notation of classs and objcts, a thing instanc is dnotd in OPM by a rctangl or an llips within which th class nam is writtn as :ClassNam. Th idntifir of th instanc can optionally prcd th colon. Th OPL syntax for an instanc maks us of th rsrvd word th in an

13 140 Rinhartz-Brgr & Dori instanc phras, which is Th ClassNam InstancNam. For xampl, suppos in Figur 3 w rplac Rtailr by Storx, an instanc of Rtailr. In th objct instanc box in th OPD w would writ Storx: Rtailr, and instad of th OPL sntnc Following path rtail, Rtailr handls Ordr Cration. w would writ Following path rtail, th Rtailr Storx handls Ordr Cration. If th instanc idntifir is not xplicitly spcifid, th OPL instanc phras would b Th ClassNam instanc. In our xampl th sntnc would b Th Rtailr instanc handls Ordr Cration. A procss can b atomic, squntial, or paralll. An atomic procss is a lowstlvl, lmntary action that is not dividd into sub-procsss, whil squntial and paralll procsss ar rfind (usually through in-zooming) into svral squntial or paralll sub-procsss. Th tim lin in an OPD flows from th top Figur 4. SD2.1, in which Rtailr Ordr Handling is in-zoomd Ordr xhibits Ordr Status. Ordr Status can b supplid or paid. Paid is initial. Product Catalog is nvironmntal. Ordr Typ can b customr or rtailr. Rtailr Ordr Handling occurs if Ordr Typ is rtailr. Rtailr Ordr Handling rquirs 2 Product Catalogs. Rtailr Ordr Handling zooms into Paying and Supplying, which ar xcutd in paralll. Paying changs Ordr Status to paid. Supplying changs Ordr Status to supplid. Figur 5. SD2.2, in which Customr Ordr Handling is in-zoomd Ordr xhibits Ordr Status. Ordr Status can b cratd, which is th dfault, supplid, or paid. Cratd is initial. Cratd lasts 2 sconds to 30 sconds. Paid is initial. Product Catalog is nvironmntal. Ordr Typ can b customr or rtailr. Customr Ordr Handling occurs if Ordr Typ is customr. Customr Ordr Handling rquirs 2 Product Catalogs. Customr Ordr Handling zooms into Paying and Supplying. Paying changs Ordr Status from cratd to paid. Supplying changs Ordr Status from paid to supplid.

14 A Rflctiv Mta-Modl of Objct-Procss Mthodology 141 of th diagram downwards. Hnc, th vrtical axis within an in-zoomd procss dfins th xcution ordr: Th sub-procsss of a squntial procss ar dpictd in th in-zoomd fram of th procss stackd on top of ach othr with th arlir procss on top of a latr on. Analogously, sub-procsss of a paralll procss appar in th OPD sid by sid, at th sam hight. In Figur 4 and Figur 5, Rtailr Ordr Handling and Customr Ordr Handling ar rspctivly in-zoomd, to show thir two sub-procsss, Paying And Supplying. In th in-zoomd vrsion of Customr Ordr Handling (Figur 5), Paying And Supplying ar xcutd in a srial ordr: first, th Customr pays and only aftrwards Ordr is supplid. In th in-zoomd vrsion of Rtailr Ordr Handling (Figur 4), on th othr hand, Paying And Supplying ar xcutd indpndntly and may occur in paralll. Th dfault xcution ordr is th squntial on, so only th paralll xcution ordr is spcifid in OPL using th rsrvd phras which ar xcutd in paralll. For xampl, th in-zooming sntnc in Figur 4 is Rtailr Ordr Handling zooms into Paying And Supplying, which ar xcutd in paralll. OPM Stats A stat is a situation in which an objct can b for som priod of tim. At any point in tim an objct is in xactly on of its stats. A stat can b a valu from a continuous or discrt valu rang, or a finit numratd st of namd stats. Ordr Status in Figur 2, for xampl, has four possibl, top-lvl stats: cratd, paid, supplid, and compltd. A stat can b initial, final, or dfault. Both cratd and paid ar initial stats, as dnotd by th thick bordrlin roundd cornr rctangl. This implis that Ordr Status can b gnratd in ithr its cratd or paid stats, but not at both, sinc at any point in tim an objct is in xactly on of its stats. If not othrwis spcifid, Ordr will b gnratd in its cratd stat as dnotd by th dfault mark (th small downward diagonal arrow that points towards th cratd stat). Th compltd stat is th final stat of Ordr Status, as dnotd in Figur 2 by th doubl lin roundd cornr rctangl. Whn ntring this final stat, Ordr can b consumd (i.., dstroyd or dltd). Th rsrvd OPL phrass that dscrib initial, final, and dfault stats ar is initial, is final, and which is th dfault, rspctivly (s Figur 2). Lik procss durations, stat durations can also b limitd on on or both sids. For xampl, th cratd stat of Ordr Status in Figur 2 has a minimal tim limit of 2 sconds and a maximal tim limit of 30 sconds, implying that btwn

15 142 Rinhartz-Brgr & Dori Figur 6. SD2.2.1, in which Paying of Customr Ordr Handling is inzoomd Product Catalog is nvironmntal. Ordr Status can b cratd, which is th dfault, or paid. Cratd is initial. Cratd lasts 2 sconds to 30 sconds. Paid is initial. Paid can b advanc paid, which is th dfault, or compltly paid. Advanc paid is initial. Paying rquirs 2 Product Catalogs. Paying zooms into Advanc Paying and Complt Paying. Advanc Paying changs Ordr Status from cratd to advanc paid. Complt Paying changs Ordr Status from advanc paid to compltly paid. 2 to 30 sconds must pass from th momnt Ordr Status ntrs its cratd stat until it xits this stat. Lik objcts and procsss, stats can b simpl or complx. Complx stats rcursivly contain nstd stats, and th innr composition of a complx stat can b xposd by zooming into it. In Figur 2, for xampl, in its paid stat, Ordr Status can b at on of two sub-stats: advanc paid, which is th dfault of a paid Ordr, or compltly paid. Th in-zoomd diagram of Paying (of Customr Ordr Handling) in Figur 6 shows that Advanc Paying first changs Ordr Status from cratd to advanc paid, and thn Balanc Paying changs Ordr Status from advanc paid to compltly paid. OPM Links Links ar th glu that holds ntitis (procsss and objcts with thir stats) togthr and nabls th construction of systm moduls of vr growing complxity. OPM links ar classifid into two typs: structural links and

16 A Rflctiv Mta-Modl of Objct-Procss Mthodology 143 procdural links, with th lattr spcializing into nabling, transformation, and vnt links. OPM Structural Links A structural link dnots a structural, that is, a static, tim-indpndnt rlation btwn two lmnts. It usually conncts two objcts, but it can also connct two procsss. Structural links furthr spcializ into gnral (taggd) structural links, and four fundamntal structural links. A taggd structural link can b unidirctional, graphically symbolizd by, or bi-dirctional, graphically symbolizd by. It is usually labld by a txtual forward tag (for th unidirctional link) or a pair of forward and backward tags (for th bidirctional link). Ths tags ar st by th systm architct to convy a maningful rlation btwn th two linkd ntitis. In Figur 2, for xampl, th two objcts Ordr and Prson ar linkd with a gnral unidirctional, structural link taggd is placd by, conncting an Ordr with th Prson who placd it. Similarly, Ordr and Coopration ar linkd with a taggd unidirctional, structural link that is also labld is placd by. Th four most prvalnt and usful OPM structural rlations ar trmd fundamntal structural rlations and ar assignd various triangular symbols placd along th lin linking th two things. Ths symbols ar graphically mor distinct and appaling to th y than thir txt tag countrparts. Th fundamntal structural links ar: 1. Aggrgation-Participation dnots th fact that a thing aggrgats (i.., consists of, or compriss) on or mor (lowr-lvl) things, ach of which is a part of th whol. It is dnotd by, an quilatral triangl whos tip is linkd to th whol and whos bas is linkd to th parts. To achiv th sam smantics, w could us consists of and is part of as th forward and backward tags of a taggd bi-dirctional, structural link, rspctivly, but, as notd, using th black triangl symbol hlps distinguish this rlation from any othr taggd structural rlation (and th othr thr fundamntal structural rlations). In Figur 2, Ordr consists of optional (0 or mor) Ordr Lins, as th multiplicity constraint * dnots. 2. Exhibition-Charactrization dnots th fact that a link or a thing xhibits, or is charactrizd by, anothr lowr-lvl thing. Th xhibitioncharactrization symbol is. Th xhibitor is linkd to th tip of th triangl, whil th faturs (which can b attributs or oprations) ar connctd to its bas. In Figur 2, Ordr xhibits (i.., is charactrizd by) th attributs Ordr Numbr, Ordr Status, Ordr Dat, and Ordr

17 144 Rinhartz-Brgr & Dori Pric and th opration Printing, whil Ordr Lin xhibits Product and Quantity. 3. Gnralization-Spcialization (Gn-Spc) is a fundamntal structural rlation btwn two ntitis, dnoting th fact that th spcializd ntitis shar common faturs, stats, and structural and procdural links with th gnralizing ntity. Th symbol of th gn-spc rlation is, a blank triangl whos tip is linkd to th gnralizing ntity and its bas to th spcializd ntitis. In Figur 2, Supplid Ordr dfins a subclass of Ordrs whos status is supplid. Lik Ordr, Supplid Ordr has its Ordr Numbr, Ordr Status (which is always supplid), Ordr Dat, Ordr Pric, Ordr Lins, and an owning Prson or Coopration. It can also xcut th opration Printing. 4. Classification-Instantiation rprsnts a fundamntal structural rlation btwn a class of things and an instanc of that class. This typ of link is dnotd by, a triangl nclosing a solid circl, th tip of which is linkd to th class, whil its bas to th instancs. Ordr 123 in Figur 2 is an instanc of an Ordr whos status is paid. Structural links of th sam typ can b connctd by OR and XOR logical rlations to spcify altrnativ structurs. An OR rlation is symbolizd by a doubl dashd arc conncting th rlvant structural links, whil a XOR rlation is dnotd by a singl lin, dashd arc. In Figur 2, for xampl, an Ordr is placd by ithr a Prson or Coopration, but not by both. If thr wr no arcs in that spcification, a spcific Ordr would hav an owning Prson and an owning Coopration. OPM Procdural Links A procdural link rprsnts a dynamic rlation btwn a procss and an ntity. Procdural links ar dividd into nabling links, transformation links, and vnt links. An instrumnt link is an nabling link that conncts a procss with an nablr of that procss. Th nablr is an ntity that must b prsnt in ordr for that procss to occur, but it is not transformd as a rsult of th procss occurrnc. Th instrumnt link can originat from an objct, a procss, or a stat, dnoting that th objct xistnc, th procss xistnc, or th objct in th spcific stat is th nablr, rspctivly. Graphically, an instrumnt link is symbolizd by, whil txtually it is rprsntd by th rsrvd word rquirs. In Figur 1, for xampl, Product Catalog is rquird for th Ordring procss. Howvr, th occurrnc of Ordring dos not affct Product Catalog in any way. Thrfor, Product Catalog is an instrumnt

18 A Rflctiv Mta-Modl of Objct-Procss Mthodology 145 of th procss Ordring. It is, howvr, possibl that for anothr procss, such as Catalog Updating, Product Catalog would b an affct, that is, an objct affctd by Catalog Updating. Hnc, bing an instrumnt for a crtain procss class can b though of as a rol of a thing class with rspct to that particular procss class. A transformation link dnots that a thing is transformd by th occurrnc of a procss. Transformation is a gnralization of consumption, rsult, and ffct. A consumption link is a transformation link that conncts an ntity to a procss from th consumd ntity that consums it. A consumption link is dnotd by to th procss, whil th rsrvd word consums rprsnts it in OPL. In Figur 3, for xampl, Product Rqust is an objct that is intrnal to Ordring (in objct-orintd programming trms it can b thought of as a local variabl of th mthod Ordring) and hnc it appars in th in-zoomd fram of Ordring. Product Rqust is consumd by th procss Ordr Vrification. In othr words, Product Rqust, which had xistd bfor an occurrnc of Ordr Vrification, was consumd (dstroyd or dstructd) by th xcution of that procss, and it no longr xists aftr Ordr Vrification is ovr. A consumption link originating from a stat of an objct mans that th procss consums that objct only whn th objct is in that spcific stat. Th corrsponding stat-spcifid consumption OPL sntnc is Procss consums stat Objct. A rsult link is a transformation link that dnots a cration of a procss, an from objct, or an objct at a spcific stat. It is symbolizd in an OPD by th procss to th rsultant ntity, whil th rsrvd word yilds dnots it in OPL. In Figur 3, for xampl, Ordr Vrification, which consumd Product Rqust, crats an Ordr. Th Ordr had not xistd bfor th bginning of Ordr Vrification. Rathr, it was cratd during this xcution, and it xists as soon as Ordr Vrification is finishd. Sinc a procss is a pattrn of bhavior or xcution, it is also possibl for a procss to gnrat or consum not just an objct but also a procss (.g., whn a procss gnrats a computr program that rprsnts a procss). To avoid, namly solid confusion, th arrowhad pointing at th consuming procss is (black) rathr than blank. Hnc, mans that th right procss mans that th lft procss yilds th consums th lft on, whil right on. An ffct link conncts a procss with a thing that is affctd, that is, undrgos whr a chang, during that procss. Th ffct link, dnotd in an OPD by th black arrowhad points towards th procss and th blank arrowhad points towards th affct (th affctd thing), mans that th affct of th procss had xistd bfor th procss occurrd and it continus to xist aftr th procss was finishd, but at last on of its stats or faturs has changd.

19 146 Rinhartz-Brgr & Dori OPL uss th rsrvd word affcts to rprsnt ffct links. In Figur 3, for xampl, Rtailr Ordr Handling and Customr Ordr Handling affct Ordr. Figur 4 rfins this ffct (stat chang) by xplicitly showing that Paying of Rtailr Ordr Handling changs Ordr Status from any stat to paid and Supplying changs Ordr Status from any stat to supplid. Figur 5 spcifis that Paying of Customr Ordr Handling changs Ordr Status from cratd to paid, whil Supplying of Customr Ordr Handling changs Ordr Status from paid to supplid. Ths rfinmnts ar mad possibl du to th ability to split an ffct link into an input (stat consumption) link and an output (stat rsult) link. Ovrall, th maning of input and output links can b thought of as th procss consums th input stat and yilds th output stat. Howvr, th objct as a whol is nithr consumd nor gnratd it mrly changs its stat (or its valu). Supprssing th objct s stats is an abstraction that hids th stats, whil also joining th input and output links to an ffct link. Procdural links can hav multiplicity constraints lik thir structural countrparts. For xampl, in Figur 1, Ordring rquirs 2 Product Catalogs whil yilding on Ordr (th dfault, whn no multiplicity constraint is indicatd) and on Rcipt. Lik structural links, procdural links of th sam typ can b groupd by OR and XOR connctors to dnot diffrnt possibl instrumnts, consums, rsults, and/or affcts of th sam procss. In Figur 3, for xampl, Rcipt Gnrating can chang Ordr Status from ithr paid or supplid to compltd. A procdural link may hav on or mor path labls. A path labl is a charactr string labl on a procdural link that rmovs th ambiguity arising from multipl procdural links outgoing from th sam ntity. Whn procdural links that originat from an ntity ar labld, th on that must b followd is th on whos labl is idntical with th labl of th procdural link through which that ntity was rachd. Th path labls in Figur 3, for xampl, spcify two possibl scnarios of Ordr Cration. Symbolizd by th path labl individual, this procss occurs at th Customr rqust and it crats a tmporary Ordr Typ objct at stat customr. Symbolizd by th path labl rtail, th procss occurs at th Rtailr rqust and it crats th tmporary Ordr Typ objct in its rtailr stat. Th Product Rqust is gnratd in both scnarios. Th Customr Ordr Handling and Rtailr Ordr Handling procsss occur according to th Ordr Typ, as th conditional nabling links (th instrumnt links with th lttr c insid thm) dnot. A conditional nabling link spcifis a branching control construct. If ths links wr rplacd by rgular nabling (i.., instrumnt) links, th smantics would b wait until Ordr Typ is in its rtailr stat and thn xcut Rtailr Ordr Handling. Aftrwards, wait until Ordr Typ is in its customr stat and thn xcut Customr Ordr Handling.

20 A Rflctiv Mta-Modl of Objct-Procss Mthodology 147 Any typ of procdural link (xcpt for th rsult link) can b mad conditional. Graphically, this is don by adding th lttr c to th link symbol, as shown in Appndix B. In OPL, a conditional procdural link is spcifid by two sntncs: on for its procdural aspct (.g., an nabling sntnc: Procss rquirs Objct. ) and th othr is a condition sntnc. Th two possibl condition sntncs ar a thing condition sntnc: Procss occurs if Thing xists. and a stat condition sntnc: Procss occurs if Objct is stat. OPM Evnt Links An vnt is a significant happning in th systm that taks plac during a particular momnt in th systm s lifcycl, and it oftn triggrs som procss in th systm. An vnt is rprsntd by an vnt link, which is a procdural link that conncts a sourc ntity with a dstination procss. Following th Evnt- Condition-Action paradigm, th smantics of an vnt link is that th sourc ntity attmpts to triggr th dstination procss. Th procss dos not start unlss th vnt link is nabld, that is, th vnt occurs, and all th procss prconditions, rprsntd by th rgular (conditional or non-conditional) procdural links, ar satisfid. Thr ar fiv typs of vnt links: 1. Agnt link: an agnt is an intllignt objct, a human or a group of humans, such as a dpartmnt in an organization, who initiats a procss by supplying an input signal (.g., pushing a button or oprating a machin) or supplying control data. An agnt link is an vnt link that conncts an agnt with th procss it triggrs. Th Ordring procss in Figur 1 starts only whn on of its agnts, th physical and nvironmntal (xtrnal) Customr or Rtailr, nabls its occurrnc. Th OPD symbol of an agnt link is from th agnt to th triggrd procss. In th OPL paragraph, this link is rprsntd by th rsrvd word handls. 2. Stat chang vnt links: th fact that an objct is at som stat is a possibl triggr for an vnt. In a stat chang vnt, th actual vnt can happn at any point in tim btwn ntranc to th stat and xit from it. A stat chang vnt link conncts an objct stat with th procss it triggrs whn ntring or xiting th stat. An nabling stat chang link is symbolizd by, whil a consumption stat chang link by. A stat chang vnt has a timing attribut that dtrmins at what point in tim th vnt occurs along th stay of th objct at th stat. Th possibl valus of th timing attribut ar any, ntranc, xit, and switch. Th any stat chang vnt is an vnt that can occur at any point in tim

21 148 Rinhartz-Brgr & Dori during th stay of th objct at th stat. Th stat ntranc vnt occurs upon th objct ntring th stat, whil th stat xit vnt mans that th vnt occurs upon th objct xiting (laving) th stat. Th stat switch vnt mans that th vnt occurs upon th objct ithr ntring th stat or xiting it. Th timing of th vnt is dnotd graphically by th timing bar a small bar prpndicular to th vnt link, whos location along th link from th triggring stat to th triggrd procss symbolizs th point in tim at which th vnt occurs. Thus, an nabling stat ntranc vnt link is symbolizd by, whil a consumption stat ntranc vnt link is symbolizd by. An nabling stat xit vnt link is symbolizd by and a consumption stat xit vnt link is symbolizd by. Timing bars at both nds of th link dnot a switch (ntranc or xit) stat vnt link, whil no bar at all mans a stat chang vnt link, whr th vnt can tak plac at any point in tim during th objct s stay at th stat. In OPL, a triggring sntnc is addd to th OPL sntnc rprsnting th procdural aspct of th link. Archiv Updating in Figur 7, for xampl, is triggrd whnvr Ordr Status ntrs its compltd stat. Two OPL sntncs dscrib this link: th nabling sntnc Archiv Updating rquirs compltd Ordr Status. and th triggring sntnc Ordr Status triggrs Archiv Updating whn it ntrs compltd. For a stat xit vnt link, th OPL sntnc would b Ordr Status triggrs Archiv Updating whn it xits compltd. For a stat chang vnt link that dos not spcify whthr th vnt occurs upon ntry to or xit from th stat, th corrsponding sntnc would b Ordr Status triggrs Archiv Updating whn it is compltd. For a stat switch vnt link, which spcifis that th vnt occurs ithr upon ntry to or upon xit from th stat, th corrsponding sntnc would b Ordr Status triggrs Archiv Updating whn it ithr ntrs or xits compltd. 3. Gnral vnt links: a gnral vnt can b an xtrnal stimulus, a chang in an objct stat or valu, and so forth. Th sourc of a gnral vnt link is a thing (objct or procss). In Figur 7, for xampl, a gnral vnt link spcifis a rquirmnt that th Log Rcording procss is triggrd any tim Ordr Status changs its stat. This singl link could b rplacd by fiv stat ntranc vnt links from ach on of th bottom lvl stats of Ordr Status, but th notation in Figur 7 is mor compact. Th Log Rcording procss dos not chang Ordr Status, as th nabling aspct (th circl) of th vnt link,, dnots. A gnral vnt link can also b of typ consumption, symbolizd by, or ffct, symbolizd by, dnoting that th sourc objct or procss is rspctivly consumd or affctd by th triggrd procss. Th OPL sntnc that spcifis th

22 A Rflctiv Mta-Modl of Objct-Procss Mthodology 149 triggring aspct of a gnral vnt link is Thing triggrs Objct. (for xampl, Ordr Status triggrs Log Rcording. ). 4. Invocation link: an invocation link is a tim-dlimitd vnt link btwn two procsss an invoking procss and an invokd on. As notd, th vrtical axis in an OPD dnots th tim lin within an in-zoomd procss. Th invocation link is usd whn this dfault procss squncing nds to b ovrriddn, as in loops or jumping instructions. Using th timing bar symbol, an invocation link can triggr th invokd procss whn th, nds, dnotd by, starts or invoking procss starts, dnotd by nds, rprsntd by, or at any tim during its xcution, rprsntd. Figur 7 spcifis that Log Rcording is triggrd any tim by Printing trminats. All th possibl OPL invocation sntncs ar spcifid in Tabl 5 in Appndix B. 5. Timout vnt link: a timout vnt link is a tim-dlimitd link that conncts a timd lmnt, which can b a procss, a stat, or an vnt link, with a procss that is triggrd whn th lmnt violats its tim Figur 7. SD3, in which Ordr is unfoldd, showing its oprations and vnt triggrs Ordr xhibits Ordr Status, as wll as Timout Rporting, Printing, Log Rcording, and Archiv Updating. Ordr Status can b cratd, which is th dfault, paid, supplid, or compltd. Cratd is initial. Cratd lasts 2 sconds to 30 sconds. Paid is initial. Paid can b advanc paid, which is th dfault, or compltly paid. Advanc paid is initial. Compltd is final. Ordr Status triggrs Log Rcording. Ordr Status triggrs Archiv Updating whn it ntrs compltd, with a raction tim of 2 sconds to 5 minuts. This link triggrs Timout Rporting whn its raction tim lasts mor than 5 minuts. Ordr Status triggrs Timout Rporting whn cratd lasts mor than 30 sconds. Timout Rporting yilds Timout Mssag. Printing triggrs Log Rcording whn it nds. Log Rcording rquirs Ordr Status. Log Rcording yilds Log Rcord. Archiv Updating rquirs compltd Ordr Status. Archiv Updating affcts Archiv.

23 150 Rinhartz-Brgr & Dori constraints. Th timd lmnt is constraind by minimal and/or maximal tim limits. Ths constraints limit procss xcution, stat duration, or th raction tim btwn triggring a procss by an vnt link and th actual bginning of th triggrd procss. Th timing bar dnots whthr rfrnc is mad to th violation minimal, maximal, or ithr on of th two tim constraints. Whn th timd lmnt (timd procss, timd stat, or timd vnt link) violats its minimal tim constraint, th minimal timout vnt link, dnotd by, is followd. Whn th lmnt violats its maximal tim constraint, th maximal timout vnt link, dnotd by, is followd. Th symbol rprsnts a timout vnt link which is followd whnvr an xtrm tim constraints is violatd, whil rprsnts an unspcifid timout violation vnt. Th squar had of th timout vnt link points towards th triggrd procss. Th cratd stat of Ordr Status in Figur 7, for xampl, is spcifid to last 2 to 30 sconds. If it lasts mor than 30 sconds, it triggrs th Timout Rporting procss, announcing th occurrnc of a timout rror. All th possibl OPL timout sntncs ar spcifid in Tabl 5 in Appndix B. As notd, an vnt link can hav minimal and maximal raction timout constraints: if th triggrd procss dos not start within th intrval (minimal tim constraint, maximal tim constraint) aftr a stimulus occurrd, a timout vnt occurs. In Figur 7, for xampl, Archiv Updating should b triggrd within 2 sconds to 5 minuts aftr Ordr Status ntrs its compltd stat. If Archiv Updating is not triggrd within 5 minuts from that vnt, Timout Rporting is triggrd, announcing th raction timout rror. OPM Rflctiv Mta-Modl Up until now w hav prsntd OPM in a rathr informal way and accompanid th introduction with a running xampl. W dvot th scond part of this chaptr to a formal rflctiv modl of OPM. OPM is itslf a complx systm that combins languag constructs and an approach to us that languag. As such, it is amnabl to modling with any modling languag that is sufficintly xprssiv. In particular, it can b modld in trms of OPM itslf, yilding th OPM rflctiv mta-modl. Th rst of this chaptr prsnts th languag and notation parts of th OPM mta-modl. As notd, th dvlopmnt part of OPM is th focus of Dori and Rinhartz-Brgr (2003) and, hnc, is not dscribd hr.

24 A Rflctiv Mta-Modl of Objct-Procss Mthodology 151 Th Top Lvl Spcification Th systm diagram (SD), which is th top-lvl, most abstract spcification of th OPM mta-modl, is prsntd in Figur 8. SD contains OPM and its faturs, which ar th attributs Languag and Notation, and th opration Systm Dvloping. Systm Dvloping, which rprsnts th ntir OPM-basd st of procsss, is handld by th Usr, who is th agnt of Systm Dvloping. This Usr can b th systm architct, dvlopr, or any othr stakholdr who uss OPM to architct, dvlop, and volv a Systm, as wll as a tam consisting of ths stakholdrs. Th Systm Dvloping procss rquirs OPM s Languag and Notation as instrumnts (unchangabl inputs) to crat a nw Systm. OPM s Languag ncompasss OPM lmnts, thir faturs, and th structural and procdural links among thm, but it dos not spcify anything about th symbols usd to dnot thm. Th Notation rprsnts th Languag both visually, through intrconnctd OPD symbols, and txtually, through OPL paragraphs and sntncs. Unfolding Notation, SD1 (shown in Figur 9) xposs th dtaild rlationships btwn Languag and Notation. Notation is charactrizd by Modality, which has two possibl stats: graphical and txtual. An OPD Symbol is a Notation th Modality of which is graphical, whil an OPL Sntnc is a Notation th Modality of which is txtual. An OPD Symbol graphically rprsnts an OPM Elmnt, th building blocks of th Languag, whil an OPL Sntnc txtually rprsnts svral Elmnts. An OPL Figur 8. SD, th top lvl spcification, of th OPM rflctiv mta-modl OPM xhibits Languag and Notation, as wll as Systm Dvloping. Notation rprsnts Languag. Systm Dvloping rquirs Languag and Notation. Systm Dvloping yilds Systm. Usr is nvironmntal and physical. Usr handls Systm Dvloping.

25 152 Rinhartz-Brgr & Dori Figur 9. SD1, in which OPM Notation is unfoldd Languag consists of Elmnts. Notation xhibits Modality. Modality can b graphical or txtual. Notation rprsnts Languag. OPD Symbol is a Notation, th Modality of which is graphical. OPD Symbol graphically rprsnts an Elmnt. OPL Sntnc is a Notation, th Modality of which is txtual. OPL Sntnc consists of at last on OPL Phras. OPL Phras consists of optional OPL Phrass and optional Atomic OPL Phrass. Atomic OPL Phras txtually rprsnts an Elmnt. OPL Sntnc txtually rprsnts at last on Elmnt. Sntnc may consist of svral OPL Phrass, ach of which can b an Atomic OPL Phras or a complx OPL Phras, that is, on that consists of othr OPL Phrass. An Atomic OPL Phras txtually rprsnts a singl OPM Elmnt. Elmnt Mta-Modl Figur 10 shows th third OPD of th OPM mta-modl, labld SD2, in which Languag is unfoldd. It spcifis that Languag consists of Entitis and Links, ach of which is an Elmnt. An Entity, which xhibits (i.., is charactrizd by) a Nam, spcializs into a Thing and a Stat. A Thing furthr spcializs into an Objct and a Procss. Th structural rlation btwn an Objct and a Stat rprsnts that an Objct owns som Stat, whil a Stat spcifis th status of an Objct. A Link xhibits Homognity, which is homognous for a Structural Link (that usually conncts two Objcts or two Procsss) and nonhomognous for a Procdural Link that usually conncts an Objct and a Procss. Th various typs of links ovrrid this Homognity attribut whn rquird. Each Elmnt is charactrizd by thr orthogonal attributs: