324 E-Business Planning and Analysis Framework Online Service: The provision of an intan- gible value-adding activity using Internet-based technology. Quality Function Deployment (QFD): A tool for converting user requirements into functional requirements that facilitates trade-off analysis, benchmarking, and deployment of requirements IURPDKLJKOHYHOGRZQWRDGHWDLOHGVSHFL¿FDWLRQ It attempts to build-in quality from the initial stages of any systems development project. Systems Development Lifecycle: A logical and iterative sequence of activities that highlight the phases of any development project. These phases typically include analysis, logical design, physical design, test, measurement and implemen- tation, and maintenance, and are often performed as concurrently as possible. Value Chain Analysis (VCA): A tool for map- ping business processes that are either primary to the business operations or serve as support processes. Variants of the model are produced for service and manufacturing sectors. This work was previously published in Encyclopedia of E-Commerce, E-Government, and Mobile Commerce, edited by M. Khosrow-Pour, pp. 264-271, copyright 2006 by Information Science Reference (an imprint of IGI Global). 325 Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 2.2 E-Business Reference Models 9RMLVODY%0LãLü University of Manitoba, Canada J. Leon Zhao University of Arizona, USA ABSTRACT A number of reference models have been pro- posed to facilitate the development of e-busi- ness systems and applications. A comparative analysis of existing models and their pertinent FKDUDFWHULVWLFVVKRXOGEHWKH¿UVWVWHSLQVHOHFWLQJ the right one to be used as the foundation for the system being developed. This chapter addresses that goal through an exposition of different refer- ence models to be used for the development of e-business systems and applications, as well as of suitable quality evaluation frameworks to be used for their assessment. INTRODUCTION Electronic business (or e-business, for short) may EH VXFFLQFWO\ GH¿QHGDVWKHDELOLW\ WR SHUIRUP exchanges of goods, services, content, assets and money, using electronic tools and techniques (Zwass, 1994). E-business transactions may be conducted by individual customers, businesses LQFOXGLQJQRQSUR¿WRUJDQL]DWLRQVDQGYDULRXV governmental agencies and departments. The main promises of e-business include cost reduc- tion, new ways of accessing customers and the ability to overcome geographical distance and other physical obstacles. In order for all these EHQH¿WVWREHUHDOL]HGDQGIRUWKHGHYHORSPHQW of e-business systems to be ultimately successful, proper foundation is needed—part of which is the use of suitable models. The concept of a model has at least two mean- ings in the study of e-business. Those meanings are distinct yet not altogether mutually exclusive, as will be seen from the following. From the business perspective, an e-EXVLQHVVPRGHOLV³D description of the roles and relationships among D¿UP¶VFRQVXPHUVFXVWRPHUVDOOLHVDQGVXS- SOLHUVWKDWLGHQWL¿HVWKHPDMRUÀRZVRISURGXFW 326 E-Business Reference Models LQIRUPDWLRQDQGPRQH\DQGWKHPDMRUEHQH¿WV to participants,” according to Weill and Vitale (2001). This concept does not differ in essence from the more traditional view of a business PRGHODV³WKHRUJDQL]DWLRQRUµDUFKLWHFWXUH¶RI SURGXFWVHUYLFHDQGLQIRUPDWLRQÀRZVDQGWKH VRXUFHV RI UHYHQXHV DQG EHQH¿WV IRU VXSSOLHUV DQGFXVWRPHUV´7LPPHUV7KXVGH¿QHG the business model provides the vision and the foundation upon which strategies to pursue their respective business goals are developed and implemented in practice. )URPWKHGH¿QLWLRQVJLYHQDERYHLWPD\VHHP that e-business is just another form of business, having the same goals as any other business and requiring the convergence of business capabili- ties in order to achieve those goals. However, WKHSUH¿[³H´LVPRUHWKDQDVLPSOHGHVLJQDWLRQ for a convenient vehicle to be used in the pursuit of those goals—it is the indication that another NLQGRIFRQYHUJHQFHLVQHHGHGWKH³FRQYHUJHQFH of multiple technologies into an integrated elec- tronic infrastructure” which is a sine qua non for conducting e-business (Weill & Vitale, 2001). The synergy of business and technology is the single most important characteristic of e-business. From the technology perspective of the IS and computer science, on the other hand, an e-busi- ness model can be understood and employed as a reference model for the development of e-business systems and applications. A reference model, as GH¿QHGE\WKH,62VWDQGDUG,62 describes a standard decomposition of a known problem domain into a collection of interrelated parts, or components, that cooperatively solve the problem; furthermore, it describes the man- ner in which the components interact in order to provide the required functions. In this manner, a reference model provides a shared mental model that facilitates learning, improves understanding and leads to better communication among all the stakeholders (Osterwalder & Pigneur, 2004). A reference model can also be used to develop PRUH VSHFLDOL]HG PRGHOV WKDW VXSSRUW VSHFL¿F requirements and scenarios, such as specialized markets or business applications. It also provides the foundation for the development of e-business systems and applications. Finally, a reference model provides the contextual framework to identify the need for, develop and coordinate related technology standards, without which ÀH[LEOH DQG LQWHURSHUDEOH HEXVLQHVV V\VWHPV ZRXOG EH LPSRVVLEOH WR EXLOG 0LãLü =KDR 2000). It is this latter meaning of the concept of an e-business reference model that we will focus on in this chapter. We stress that the need for reference models exists regardless of the particular strategy and implementation path (or paths) chosen for the development of e-business applications. Ideally, such systems and applications should be developed in a structured, top-down and architecture-cen- tric fashion (Bass, Clements, & Kazman, 2002). In practice, however, few businesses have the luxury of being able to develop their respective systems and applications in this manner, start- ing from zero (although some projects may be developed in that manner). Most of the others already utilize a multitude of existing systems and applications—often referred to using the TXDOL¿HU ³OHJDF\´²WKDW ZHUH GHYHORSHG RYHU the years on heterogeneous hardware, software and application platforms. While sometimes inadequate and most often incompatible with one another, legacy systems cannot simply be discarded since they encapsulate crucial business logic and manage vast quantities of operational data; instead, they should be integrated with one another and with newly developed e-business systems. (Such development is often referred to as evolutionary.) In both cases, the availability of a suitable model to govern the development is a necessary precondition for success. A number of reference models for the develop- ment of e-business applications have been pro- posed over the years. Developed by both individual companies and organizations and industrial con- sortia, they offer markedly different perspectives 327 E-Business Reference Models and different sets of features. Selecting the most appropriate one under a given set of requirements and constraints that hold in a given environment is a non-trivial undertaking. Therefore, the study of e-business reference models should help both researchers and practitioners to develop better and more advanced e-business application systems, and thus help implement the business vision and VWUDWHJLHVGH¿QHGE\HEXVLQHVVPRGHOV7RDLGLQ that process, this chapter provides a compendium of e-business reference models, primarily from the technology perspective, with a twofold objective: ¿UVWW RRXWOL QHW KHDYD LODEOHDUFKLW HFW X U DORSWLRQV and choices in the design of e-business applica- tions and systems, and second, to highlight the tradeoffs incurred in the selection process. Of course, an exhaustive enumeration of all models, architectures and frameworks relevant to e-busi- ness is not possible. Yet we have tried to include all the developments with theoretical and practi- cal relevance, as well as some of the others that highlight certain important aspects of e-business reference models. The remainder of the chapter is organized as follows. First, the chapter outlines the basic concepts relevant to the e-business reference models, using some of the models proposed in the literature to illustrate and clarify them. A brief historical overview of the development of e-busi- ness reference models is then given, followed by the discussion of a number of important models. Particular attention will be paid to the models that use Web services, which are quickly becoming the GRPLQDQWSDUDGLJPIRUWKHGHYHORSPHQWRIÀH[- ible, interoperable e-business systems, not least on account of their ability to integrate heterogeneous systems and applications, including legacy ones (Booth et al., 2004; Fletcher & Waterhouse, 2002; Gottschalk, Graham, Kreger, & Snell, 2002). The next section addresses the ever important issue of quality of reference modeling and presents a brief overview of a quality framework suitable for evaluating that quality. Finally, the chapter sum- marizes the chapter’s content and outlines some promising avenues for further research. CHARACTERISTICS OF E-BUSINESS REFERENCE MODELS In this section, a number of pertinent characteris- tics of HEXVLQHVVUHIHUHQFHPRGHOVDVLGHQWL¿HG E\ 0 L ãLüD Q G = K D R Z L O O E H O L V W H G G L V FX V V H G and illustrated using actual e-business models that feature them. Orientation E-business, as its very name implies, is built on the dual foundations of business and technology (Zwass, 1996). Successful development of e-busi- ness systems thus requires that both business- and technology-related issues are addressed in an interdependent way. This interdependence has been recognized since the beginnings of e-busi- ness in the early nineties, yet most of the research ZRUNUHSRUWHGVRIDUFDQUHDGLO\EHFODVVL¿HGDV primarily business- or technology-oriented. While this dichotomy is not quite unexpected—after all, e-business systems are quite complex in terms of both the number of features and the diversity thereof, and researchers themselves are not always ready to step outside their narrow area of expertise—it does play a crucial role in determining the scope and focus of much of the research work reported. In doing so, the issues related to the other side (i.e., business issues, in case of technology-oriented models, and vice versa) may be implicitly assumed to be easy or already solved. While the latter may well be the case, the former is almost never true, and may incur serious risks in later development. $VDQH[DPSOHRIDGH¿QLWHRULHQWDWLRQFRQ- VLGHUWKHFODVVL¿FDWLRQRI,QWHUQHWEXVLQHVVPRGHOV originally proposed by Timmers (1998), which is shown in Figure 1. Although, strictly speaking, it 328 E-Business Reference Models is not a reference model, it is nonetheless interest- ing on account of its clear business orientation and because it provides a useful, albeit somewhat limited, taxonomy of different e-business models. Similar taxonomies have been described by other DXWKRUV XVLQJ GLIIHUHQW FULWHULD IRU FODVVL¿FD- tion; among the better known ones are the eight atomic models described and analyzed in detail by Weill and Vitale (2001), and an exhaustive ontology of e-business models by Osterwalder and Pigneur (2004). A more detailed discussion of those taxonomies is beyond the scope of this chapter, as our primary focus is the discussion of e-business reference models as vehicles to aid and facilitate the development of e-business systems and applications. Perspective and Viewpoint Support The existence of distinct, mostly independent and (sometimes) mutually orthogonal views was recognized in several areas, in particular in relationship with architectural modeling of software-intensive systems (Bass et al., 2002; Kruchten, 1995; Shaw & Garlan, 1996). A view (often referred to as a viewpoint or perspective) attempts to describe the system from the per- spective of a related set of concerns, most often corresponding to the requirements put up by a VSHFL¿FJURXSRIVWDNHKROGHUV,(((,Q fact, even the dichotomy between business and technology orientation mentioned above can be c o n s i d e r e d a s a n i n s t a n c e o f m u l t i p l e p e r s p e c t i ve s . This approach is adopted by the ISO Open EDI 6WDQGDUGZKLFKGHVFULEHV³WZRSHUVSHFWLYHVRI business transactions” through business aspects and information technology aspects (ISO/IEC, 1998). The modeling methodology of the recent ebXML standard also distinguishes between business and information technology aspects of business transactions, described through business operational view and functional service view, respectively (Eisenberg & Nickull, 2001). However, many proposed models include more than two perspectives. According to Bussler and Jablonski (1994), descriptions of business systems commonly include functional, informational, behavioral and organizational perspectives. Tech- nology-oriented models sometimes include even more: Witness the ISO/IEC reference model for RSHQ GLVWULEXWHG SURFHVVLQJ ZKLFK GH¿QHV QR OHVV WKDW ¿YH YLHZSRLQWV HQWHUSULVH LQIRUPD- tion, computational, engineering and technology (ISO/IEC, 1992); the same number of views has EHHQLGHQWL¿HGLQWKHDUHDRIVRIWZDUHDUFKLWHFWXUH (Kruchten, 1995). Regarding e-business itself, +ROVDSSOHDQG6LQJKKDYHGH¿QHGDWRWDO RI¿YHVXFKYLHZVWKHWUDGLQJYLHZWKHLQIRUPD- tion exchange view, the activity view, the effects view and the value chain view. Therefore, a reference model of e-business should (a) account for as many different perspec- Figure 1. &ODVVL¿FDWLRQRI,QWHUQHWEXVLQHVVPRGHOV$FFRUGLQJWR7LPPHUV functional integration degree of innovation value chain integrator e-shop e-procurement e-mall e-auction trust services value chain service provider info brokerage virtual community third-party marketplace collaboration platform lower higher single function multiple functions/ integrated 329 E-Business Reference Models tives as possible, and (b) specify the perspective or (preferably) perspectives it takes into account. The former property may be considered as yet another facet of the completeness property. The reference model for electronic markets (RM-EM) proposed by Schmid and Lindemann (1998) is shown in Figure 2. This is a business- oriented model that supports multiple views, arranged to support the decomposition of a busi- ness transaction into information, agreement and settlement phases. Similar phase decomposition, but with an additional support or communication phase after the settlement, was proposed by Selz and Schubert (1998). A similar approach has been adopted by the project on Building Blocks for Electronic Com- merce (EBES/EWOS, 1997), where the concepts of sequential and hierarchical decomposition are u s e d a s t h e m a i n a n a l y t i c a l t o o l s . Bu s i n e s s a c t i v i - WLHVDUHVHTXHQWLDOO\GHFRPSRVHGLQWR¿YHVWHSV or high-level commercial processes of marketing, contracting, logistics, settlement and interface with administrations. (Notice the similarity with the RM-EM model.) These processes are, in turn, decomposed into lower-level activities referred WRDVEXLOGLQJEORFNVVXFKDV³FRQVXOWSURGXFW FDWDORJXHV´ ³UHTXHVW SULFH TXRWDWLRQ´ DQG WKH like. The technology-dependent implementation RIDEXLOGLQJEORFNLVFDOOHGD³VROXWLRQ´ZKLFK is to be integrated into appropriate applications or services; a number of integrated products or services used to provide support for one or several VXESURFHVVHV LV FDOOHG D ³VROXWLRQVHW´ 7KLV LV schematically shown in Figure 3; note the com- bination of views and layering which indicates another similarity with the RM-EM model. Layering /D\HULQJ RU VWUDWL¿FDWLRQ KDV EHHQ H[WHQVLYHO\ used as one of the main vehicles to reduce the complexity of models. Probably the best known example of layering is the ISO OSI reference model (ISO, 1984), predominantly used to describe networking systems, which has no less than seven different layers; although few actual systems use all the layers (and even the layers which are used FDQQRWDOZD\VEHXQDPELJXRXVO\GH¿QHGWKLV PRGHO LV FRQVLGHUHG DV D VLJQL¿FDQW PLOHVWRQH in the area of networking, and it is widely used in research, education and practice ever since. Note that structural properties, such as number of layers, partitioning of system functionality between them, the level of abstraction of each layer, the manner in which components interact (both within each layer and between different layers) and the like, can be used to compare and evaluate different layered models. Figure 2. Reference model for electronic markets (After Schmid & Lindemann, 1998) Functional View Business View subprocess 1 subprocess 2 subprocess n Building Block 1 Building Block 2 Building Block n EC process (phase or step) Technology View solution set n solution n.1 solution n.2 solution 2 solution 1 330 E-Business Reference Models In the e-business area, layered models have b e e n u s e d f r o m t h e ve r y b e g i n n i n g . I n f a c t , o n e of WKH¿UVWVXUYH\VRIHFRPPHUFHUHVHDUFK=ZDVV 1996) describes a three-layer, seven-sublayer framework for e-commerce. This framework, not unlike the original ISO/OSI reference model (ISO, 1984), is shown in Table 1. A similar framework, but with a different layering structure, has been proposed by Kalakota and Winston (1996). Most other e-business models are also layered, with the number of layers ranging from three to seven. Moreover, several of those models possess more than one level of decomposition, resulting in an even wider range of layers. Of course, the optimum number of layers in a reference model cannot be prescribed in advance. Technology (In)Dependence An important characteristic of e-business models, tightly coupled to the business vs. technology dichotomy explained above, is their technology independence or lack thereof. E-business sys- tems are ultimately implemented using available technology; but the models themselves should be as little dependent on any particular technol- ogy as possible. The reasons for this are nearly self-evident: Figure 3. EBES/EWOS building blocks architecture Business View Infrastructure View Service View Transaction View Business Model Mediating Catalog Contracting Tool Logistics Market Transactions and Business Scenarios Communication Infrastructure Phases of a Market Transaction Information Agreement Settlement Table 1. Hierarchical framework of e-commerce (Adapted from Zwass, 1996) meta-level level function products and structures 7 electronic marketplaces and electronic hierar- chies 6 products and systems services 5 enabling services 4 secure messaging infrastructure 3 hypermedia/multimedia object management 2 public and private communication utilities 1 wide-area telecommunication infrastructure 331 E-Business Reference Models • As the number of decisions and choices to be made in actual system implementation is large, using a model tied to a particular technology restricts those choices and de- SULYHVXVRISRVVLEOHEHQH¿WVEURXJKWRQE\ more advanced technology. On the contrary, the use of a technology-independent model provides the freedom to choose the imple- mentation technology on the basis of other FULWHULDDQGWKXVPLQLPL]HWKHFRVWEHQH¿W ratio and maximize the return on invest- ment. • The use of a model tied to a particular technology may preclude reuse of tools and components already available, thus increas- ing the cost of developing the new system. • The use of a technology-independent refer - ence model ensures its longevity, thus pro- tecting our initial investment, both monetary and intellectual, made in the development of that model. • Finally, the use of a technology-independent model facilitates the interoperability with other e-business systems and thus allows for easy integration of both existing and newly developed applications into a coherent enterprise system. Typically, models with dominant business orientation exhibit the least amount of technology LQGHSHQGHQFH $V IRU WKH PRGHOV ZLWK GH¿QLWH technology orientation, some of them are tied to a particular technology while others are not; ex- amples for both kinds of models will be provided. On the other hand, technology orientation does not automatically imply technology dependence: Some among the reference models with clear technology orientation are essentially technol- ogy-independent. This distinction essentially vindicates our approach to separately consider the dependence/independence and orientation properties. Interoperability and Openness O n e of t h e m a i n t e n e t s o f e - b u s i n e s s (a n d a n y o t h e r business, for that matter) is interaction between two or more business partners. In order to enable and facilitate the communication between their re- spective e-business systems, those systems should adhere to some protocols and standards. This decision has to be reached by consensus within the community, as there is no central authority to mandate the use of a particular protocol or standard—although such attempts often happen as vendors attempt to gain market share and force the use of proprietary standards onto the user community. Such attempts sometimes succeed, and indeed proprietary standards may sometimes offer certain advantages in terms of performance, reliability or otherwise. Yet the use of open stan- GDUGVLVFRQVLGHUHGEHQH¿FLDOLQWKHORQJWHUP if only because it avoids vendor lock-in and thus results in distinct economic advantages. Another facet of this property is openness, GH¿QHGDVWKHDELOLW\RIWKHV\VWHPWRLQWHUIDFH to other systems and actors in the outside world 0LãLü=KDR2SHQQHVVLVFHUWDLQO\ID- cilitated through the use of established and widely accepted standards and protocols. The Role of Standards We note that protocols exist almost as long as h u m an s h a v e c o m mu n i c a t e d ( a ny n a t u r al l a n g u a g e is, in essence, a general purpose protocol), and the importance of standards in industrialized society hardly needs mentioning. Yet the impe- WXV IRU GHYHORSPHQW IRUPDO VSHFL¿FDWLRQ DQG YHUL¿FDWLRQRISURWRFROVLVLQH[WULFDEO\OLQNHGWR the development of data communication through computer networks (Stallings, 2005). As a result, a number of standards for communication between independent business systems and applications h ave been pr oposed ove r t he yea rs. So me of those standards have enjoyed rather wide acceptance: SWIFT, a secure messaging standard developed 332 E-Business Reference Models DQGXVHGWKURXJKRXWWKH¿QDQFLDOLQGXVWU\,62 2004), and eectronic document interchange, or EDI, a standard for electronic document inter- change (FIPS, 1996), to name but two among the best known ones. However, the advent of the Internet and e-busi- ness, together with the characteristics of Internet communications and the underlying TCP/IP family of protocols, have introduced the need for new and improved standards. A number of standards evolved from the existing ones, or have been developed from scratch. The list includes Open EDI (ISO/IEC, 1998), Open buying on the Internet (OBI, 1999), and open trading protocol (IOTP, 1998), among others. Unfortunately, those protocols did not succeed in achieving wider acceptance, mainly on account of the following factors: • Most of those protocols cover only a frac - tion of possible e-business scenarios and activities. For example, the OBI protocol (OBI, 1999) deals with payment only, and payment is but one phase in any e-business WUDQVDFWLRQ&RQVHTXHQWO\WKHEHQH¿WV achievable through deploying such a proto- FROZHUHSHUFHLYHGDVLQVXI¿FLHQWWRRIIVHW the high initial cost in infrastructure and manpower. • As some of the new protocols were exten - sions of the existing ones (e.g., Open EDI has evolved from EDI), business that did not use the original protocols had little incentive to jump start the new ones. • The sheer number of such protocols meant that there was no clear winner in sight. Therefore, a majority of businesses were rather reserved in deploying them, deferring the costly switching to the new technology until they could be assured of widest possible interoperability. In contrast, the World Wide Web has been readily embraced by most businesses—but a universally interoper- able standard was available (HTML), and WKHFRVWVLQFXUUHGZHUHVHHQDVMXVWL¿HGLQ view of the increased reach and presence. Consequently, each developer of e-business systems was free to design its own interoperability standard without any concern regarding interoper- ability with the others. This was further aggravated by the relative immaturity of e-business, as the traditional business models and approaches were found inappropriate for the new business envi- ronment, and new modes of conducting business had to be devised, validated and perfected. Note that similar situations are quite common in many industries, in particular in information technol- ogy-related markets at an early stage—remember the number of incompatible PC-based operating systems, word processors and spreadsheets that were available in the early eighties, and compare it to the numbers available in the respective mar- kets now. However, as the markets mature, the number of competitors tends to diminish. Quite often, a new standard (or a new set of standards) appears that replaces the existing ones, either as a synthesis of their best features or merely as their least common denominator—but at least only one standard remains upon which new, interoperable systems can be built. The problems mentioned above could be ad- dressed in different ways. In one approach, stan- dards are built in a bottom-up manner, starting from the lowest common denominator that all interested parties can agree upon, and then gradually adding PRUHIXQFWLRQDOLW\DVQHHGHG6XFKD³PLQLPDO- ist” approach was adopted by the proponents of Web services, a recent interoperability standard endorsed by all major players on the market: BEA, IBM, Microsoft, Sun and others (Erl, 2004; Fletcher & Waterhouse, 2002). While the Web services paradigm provides just the bare interop- erability between applications (which means it is not too useful in practice), it also offers a common conceptual and technical foundation upon which PRGHOVDQGV\VWHPVFDWHULQJWRVSHFL¿FEXVLQHVV requirements can be built. 333 E-Business Reference Models Another approach gives preference to depth over breadth, as it attempts to leverage the advances in organizational knowledge. Namely, when new ap- plication domains arise, requirements are initially YDJXHDQG¿UVWV\VWHPVLQYDULDEO\VXIIHUIURPWKH ODFNRIIRFXVDQGZHOOGH¿QHGVFRSH$VDUHVXOW such systems, including reference models, are not very successful—as production-quality solutions, WKDWLVEXWWKH\GRDOORZXVWRFODU LI\DQGUH¿QHWKH requirements, and ultimately improve our knowl- edge. As the market matures, our knowledge of it improves—we know more about both problems and their solutions, and we can choose more promising routes to follow in solving those problems. The qualitative and quantitative improvement obtained in this manner is inversely proportional to the scope of the domain: The narrower the scope, the greater the improvement that can be achieved. This enables the development of standards and practices that GLVWLOODQGHPERG\WKDWNQRZOHGJHIRUWKHEHQH¿W RIDO O S D U W LHV L QYR OYHG 6 X F K D ³ V S H F L D O L V W ´ D S SUR D F K LVSHUKDSVEHVWH[HPSOL¿HGE\WKHGHYHORSPHQWRI two recent families of standards known as ebXML (Eisenberg & Nickull, 2001) and RosettaNet (Kak & Sotero, 2002), both of which build upon existing standards at different levels, including Open-EDI and XML (among others), while focusing on their respective application areas in depth. A more detailed description of both standards is given in Section 4. Extendibility Extendibility refers to the ability of the model to evolve over time. Evolution includes accommo- dating new or changed requirements, which may (and ultimately will) emerge over time. Require- ments may change because of new or changed business needs, technology changes due to new advances or phasing out of obsolete technologies or changes in the business environment. Yet re- gardless of their particular cause, changes must be absorbed and seamlessly integrated into the model, if it is to remain a coherent foundation for the development of e-business systems. Extend- ibility might also mean that existing standards are enriched or extended using certain new facilities: For example, the SWIFT messaging standard for ¿QDQFLDOLQGXVWU\KDVUHFHQWO\EHHQHQULFKHGZLWK appropriate UML models and XML message structure (ISO, 2004). E-BUSINESS MODELS: PAST AND PRESENT 7KLV VHFWLRQ ZLOO EULHÀ\ SUHVHQW D QXPEHU RI e-business reference models, including some that have already been mentioned, in historic succession. Early Attempts A number of early attempts at creating a reference model for e-business are worth mentioning: • The DoD electronic commerce model, in fact an extension of the EDI standard (Jo, Pottmyer, & Fetzner, 1995). • A layered model described by Kalakota and Winston (1996), which is similar to the Zwass (1996) framework mentioned above. • The EBES/EWOS model mentioned above (EBES/EWOS, 1997) was sponsored by the European Commission through EBES (Eu- ropean Board for EDI/EC Standardisation) and EWOS (European Workshop for Open Systems); both bodies were later superseded by the European Committee for Standardisa- tion (CEN). Building on Existing Pre-Internet Models Soon enough, as more experience in various aspects of e-business was obtained, a number of more mature models began to appear. . messaging standard developed 332 E-Business Reference Models DQGXVHGWKURXJKRXWWKH¿QDQFLDOLQGXVWU,62 2004), and eectronic document interchange, or EDI, a standard for electronic document. as vehicles to aid and facilitate the development of e-business systems and applications. Perspective and Viewpoint Support The existence of distinct, mostly independent and (sometimes) mutually. (Adapted from Zwass, 1996) meta-level level function products and structures 7 electronic marketplaces and electronic hierar- chies 6 products and systems services 5 enabling services 4 secure messaging infrastructure 3