1. Operations Operations managementmanagement research: some reflections on research evolution, models and 655empirical studies in OM Roberto FilippiniIstituto di Ingegneria Gestionale, University of Padua, Vicenza, ItalyThe first phase of OM researchHistory, in terms of evolution of research approaches and subjects of interest,has had its role in helping to frame the right questions to ask when teaching,researching and/or practising[1]. In his well known work, Buffa[2] suggestedthat it is possible to trace three main phases of evolutionary development in thefield of OM during the 30 year period after the Second World War. For much of the 1950s OM was called industrial management or factorymanagement. Studies were characterized by their descriptive approach.Numerous techniques were studied and put forward: time and motion study,plant layout, production control and descriptions of how production systemsworked. In this period, mathematical techniques, such as queuing theory andMonte Carlo simulation, also began to be developed and chapters on personnelmanagement, finance, marketing and organization management appeared inthe textbooks. During this phase all studies implicitly assumed that: the production system both is cut off from the environment and isstrategically neutral; it is prevalently characterized by technical features; and the final aim is that of maximizing the productivity of labour.During the 1960s, and for much of the 1970s, management science/operationsResearch (MS/OR) studies provided the scientific methodology that allowed usto develop something akin to the natural science or physics operating systems.MS/OR also opened the door to the study of service systems as a naturalbroadening of production management into the present scope of operationsmanagement. For at least 20 years we have enjoyed the pleasure of ample,researchable topics with publishing outlets in the MS/OR journals[2]. Chase[3] highlighted the fact that during the 1970s, OM research wasdominated by abstract application of techniques and rarely involved empiricalstudies; hence, they were of little real use to operations managers. He analysedInternational Journal of Operations134 papers which had appeared between 1977 and 1979 in some refereed & Production Management,Vol. 17 No. 7, 1997, pp. 655-670.journals (Decision Sciences, AIIE Transactions, Management Science, MCB University Press, 0144-3577

2. IJOPM International Journal of Production Research) and classified the articles into17,7four categories, based on two dimensions: research orientation (micro, whichdeals with isolated problems, and macro) and research emphasis (people, i.e.managerial, and equipment, i.e. technical). Chase found that 88 per cent of the articles were micro type and 76 per centemphasized equipment and were centred on questions of scheduling,656 aggregate/capacity planning, layout, quality control and inventory control.Only 12 per cent were macro-oriented. However, it is interesting to note that inthe same period there were books, and in particular textbooks, which adopted amore general perspective and a more managerial approach. For example, Chaseand Aquilano[4] proposed a more integrated approach for production andoperations management which included a temporal view of the evolution ofproduction systems. Wild[5] used a systemic approach to study operations.Whereas Skinner[6], in marked opposition to the dominant tendency of studiesto be micro/technical oriented, emphasized the strategic importance ofmanufacturing.Changes during the 1980sBy the end of the 1970s, OM had begun to be a functional field of study withinmanagement disciplines. 1980 was an important year for OM history. Indeed,both the Journal of Operations Management, voice of the OperationsManagement Association (OMA), and the International Journal of Operations &Production Management, voice of OMA-UK, were set up. In the first part of thedecade there was a marked development in OM research. Not only the twonewer journals, but also others, dedicated a lot of space to OM. In 1981, Decision Sciences published a collection of papers dealing with thestate of the art in OM. These papers emphasized the importance of certainthemes such as the development of strategic orientation. Miller and Graham[7],for example, put forward an agenda for the 1980s which was subdivided intofour main topics or areas. A similar agenda was suggested by Voss, in the UKin 1984[8]. The main areas on which OM studies were concentrated during the 1980swere identified as: Operations policy, which includes manufacturing strategy, and which analyses the reasons for success or non-success in operations. Operations control where, alongside the traditional techniques, such as MRP, new techniques, particularly JIT, attracted attention. Service operations, it had become clear that the principles underlying OM could equally well be applied to service[9,10]. Productivity and technology, here the advent of new technologies posed important problems of process design and how to use it; this issue aroused a great deal of interest and the approach was broadened with respect to earlier studies. 3. In the 1980s, the themes of total quality management (TQM) and of the so-calledOperationsJapanese techniques acquired greater importance than had been foreseen in managementresearch agendas. The concept of total quality, pioneered in the USA by Juranresearchand Deming, was rediscovered in response to the pressure of the Japanesemanufacturing approach[11]. The concept of just-in-time (JIT) was approachedboth from the descriptive angle of techniques and from their impact onperformance[12-14].657 Other signs of the way in which OM was entering the field of managementstudies during the 1980s can be found in a variety of texts such as that ofBuffa[15], Hayes and Wheelwright[16] and Skinner[17]. A multiplicity of pointsof view were adopted which drew on other areas of management, such as, theconcept of manufacturing capability as a competitive weapon andmanufacturings strategic role in corporate strategy. Some changes in the subjects of interest in refereed journals were also noted.Amoako-Gyampah and Meredith[18] analysed the articles that had appearedover the period 1982-1987 in the ten journals in which OM researchers usuallypublished. They classified these articles into 17 categories with the aim ofseeing whether there had been any change in the direction of OM research.They then compared the distribution of subjects in the period 1982-1987 withthe analogous distribution carried out by Chase for the period 1977-1979. The area of operation control continued to be dealt with in more than half thepapers published, the most common topics being MRP and productionplanning. Scheduling, while still important (20 per cent of papers), had fallenfrom the higher position (36 per cent) it had held in Chases study. Work on thetopics of process design/technology and manufacturing strategy had attractedmore attention than in the earlier period, while research on so-calledengineering techniques, work measurement, maintenance/reliability andfacility (plant) location, had lost ground. Other reviews of OM papers publishedduring the 1980s would seem to confirm these findings[19,20]. Neely[19] examined the papers published in the first ten volumes (1980-1990)of the International Journal of Operations & Production Management. UsingChases four main categories (micro versus macro and people versus equipment),Neely found that OM was emerging as a functional field of management. At thebeginning of the decade, in early volumes of IJOPM, micro/equipment topicswere paid the same percentage level of attention as in Chases study (over 70 percent). However, by mid-decade, they had fallen off considerably, whereasmacro/people topics, with a more managerial emphasis, had increased theirshare and stabilized at around 40 per cent.Recent evolutionAlready, by the end of the 1980s, the outlines of the path that OM researchwould be taking in the future had been laid down. In the USA, manufacturinghad assumed an important role within the debate about levels of competitivity;a debate which arose from the comparison of Japanese approaches toproduction with the North American approach. In Europe, too, the debate was 4. IJOPM lively: various schools of thought had come into the discussion, which was17,7developing both between academics and between practitioners. The rules for the successful management of operations were changing. Newlines of study and research were being developed and published, spurred on,above all, by production innovations being carried out by the Japanese. In thelate 1980s and early 1990s, many studies looked at the problem of production658 models, for example, studies of world class manufacturing[21,22] and the well-known study carried out by Massachussetts Institute of Technology on the autoindustry[23] which sparked off an international debate on the directionproduction systems would take in the future. These studies laid particularemphasis on organizational aspects and on the role of human resources. A further contribution to the broadening of the debate came from the interestshown by some researchers in the theme of organization, particularly from theeconomic aspect: MIT research is just one example. Some topics were approached in new ways and others took on a moreimportant role: manufacturing was recognized as being strategically very important forcompanies and manufacturing strategy received more attention[24-26]; the traditional concept of trade-off tended to be left behind[27] andattention paid to improvements in performance in the areas of time,quality and cost[28]; operations were seen in a broader, yet more integrated manner, upstreamwith suppliers and downstream with clients, according to a certain viewof systems of firms and of the relations between them[29,30]; more importance was attributed to the study of product developmentand to its relationships with manufacturing[31,32]; many studies have been carried out on JIT and TQM; these practices arenow being seen within an integrated setting and their impact onperformance is being studied. Some of these empirical studies arebeginning to use approaches and methods drawn from other managerialdisciplines and from social sciences[33-38].But precisely what changes did take place in OM studies in the early 1990s?Some researchers, such as Walton and Handfield[39], maintain that there wereno especially important changes at all. After analysing OM papers whichappeared between 1990 and 1995 in four leading journals (Decision Science,Journal of Operations Management, Management Science and Production andOperations Management) they concluded that the primary area studied in theOM literature is still inventory and scheduling, with an OR/MS approach. On the other hand, other authors, such as Voss[40], believe that there havebeen changes in OM research, both in the core discipline and in the numerousareas on which OM touches and, furthermore, that there are some differences,above all in research methods, between the situation in the USA, in Europe and,markedly, in the UK. 5. We have examined the 1996 conference proceedings of the Decision ScienceInstitute, which represent, fairly well, current research in the pipeline in theUSA. A total of 244 papers have been analysed and the results compared withthose of the study by Amoako-Gyampah and Meredith[18] which classified the1986 and 1987 conference proceedings of the Decision Science Institute into 17OM topic areas. The results of this comparison are summarized in Table I.Category Pipeline research 1986/87 Pipeline research 1996Inventory control/MRP/JIT17.577.99Aggregate planning4.050.84Forecasting 4.730.42Scheduling/MPS/SFC 16.89 15.55Capacity planning 0.680.42Purchasing (supply chain) 6.083.78Facility location 2.700.84Facility layout 0.000.84Process design/technology14.19 16.80Maintenance 3.381.68Quality 6.08 19.33Work measurement0.000.84Strategy6.76 13.86Distribution2.030.42Table I.Quality of working life 0.000.42Classification by topic ofProject management0.680.42the DSI proceedingsServices 14.18 15.55 1986/87 and thoseTotal 100.00100.00of 1996As the Table illustrates, in 1996 some issues were receiving less attention thanin the past: inventory control, cut by more than half, aggregate planning andforecasting. Less attention was paid to purchasing, too, and papers in this areaemphasized the new issues of the supply chain. There was little change asregards scheduling and services. Slightly more space was allocated to processdesign/technology (from 14.19 per cent to 16.8 per cent). Here, as well as paperson more traditional themes, there were also papers on product development andhuman resource management in the much discussed advanced technologies. However, there was a marked increase in interest in questions of quality(from 6.08 per cent to 19.33 per cent) which encompass numerous issuesincluding quality control, ISO 9000 and TQM. The question of quality was alsotaken up from an integrated and interfunctional angle, for example, the study ofthe relation between quality and performance, or between quality, suppliersand product design. Within this topic there were many surveys (47 per cent ofthe total) and theoretical, conceptual studies (24 per cent). The strategy issue attracted more attention than before (from 6.76 per cent to13.86 per cent) and many papers approached the question from aninterfunctional point of view, for example: best practices and 6. IJOPM performance/competitiveness; manufacturing strategy and environmental17,7management; manufacturing strategy and product development.Many of the papers presented at the 1996 DSI meeting were of aninterfunctional nature. They took up the theme of the relationship betweentechnological and managerial variables, examining them from both theoperational and the strategic points of view. In some cases this made it difficult660 to find the most appropriate category for such papers within the traditional 17topic areas which have, until now, been used to classify research papers. In thefuture it may well be worth considering some issues separately, for example:product development, practice-performance relationship, performancemeasurement, management of technology and environmental management.Thus, comparing of DSI conference proceedings after a ten year interval hasserved to highlight some interesting changes that have taken place. Obviously,it is impossible to foresee when and to what degree such changes will bereflected in the papers published in journals.Lastly, it should be mentioned that six papers have been omitted from thetable. These papers dealt with the topic of OM research and methods forempirical research, including the problems of measuring variables in the field ofoperations.Models, theories and empirical research in OMHowever, merely analysing evolution and trends in publication is not enough ifone is seeking to understand fully research requirements and potentialperspectives. Such requirements derive both from the questions that researchitself poses for the future and, given that OM is very much an applied discipline,from the need to offer answers to the concrete problems that emerge within bothindustry and services. The current evolution of competition between firms atthe international level, the search for cost reduction together with timereduction, the challenge posed by global markets which even SMEs must faceand the development of networks of firms, all pose new problems of strategyand practice for firms. Future developments in a discipline must also be evaluated in the light of thelevel of models and theories and in the need for them. Some researchers, in particular Flynn et al.[41], Meredith et al.[42],Swamidass[43] and Meredith[44], maintain that one of the main problems forOM research lies in the paradigms, theories and empirical research methodsused. This opinion is probably not shared by other OM researchers, particularlythose who mainly study the applied aspects of the discipline and do not thinkthat generating theory is a fundamental task for OM. However, given that OM is a discipline which is concerned with the selection,adoption and management of new technologies and socio-technical systems, wewould agree with those who believe that there must be progress at the level ofmodels and theories, too, especially if these are developed on the basis ofempirical study. It would seem crucial that there be theories available which 7. make it possible to design and manage complex systems and which enable the Operationsexisting relationships between the technical and organizational variables to be managementexplained. Theory can offer models which help in decision making even in the researchpresence of uncertainty and variability, because they help in predicting thepossible consequences of alternatives: for example, theory regarding productinnovativeness and success in the marketplace, or theory about the differenttypes of manufacturing strategy and the conditions under which they can be 661applied, or, theory of total quality management in the context of other theoriesabout the firm. Just as in other applied sciences, OM could benefit from theories which helpto explain phenomena and the relationships between relevant variables. Ingeneral the characteristics that a theory should have are: it must specify thevariables it considers and their relationships and must offer criteria for definingits boundaries. It must add to the existing body of knowledge about aphenomenon[45,46]. The predictive element, intrinsic to a good theory, isindubitably important but that of explanation is even more crucial. It isgenerally accepted that the only valid result of scientific theory is adequateexplanation. This means defining the theory well at the conceptual level(variable definition must be conceptual, domain specified, relationshipspecified) and then checking the theory empirically. There are three phases involved in developing a theory[44,47]. Thedescription phase allows the elements that are of interest to be characterized.Exploratory research, based on preliminary, descriptive research is very usefulin this phase. The second phase, called the explanation phase, entails the construction of aframework which defines and justifies the relations between the variables. Itmust be constructed and described in such a way as to generate testablehypotheses and to allow successive empirical studies to be carried out. Thisexplanation phase has been neglected often in those OM studies where acomplex phenomenon has been simplified and solved with an algorithmicmodel, thus ignoring important aspects of the real world. For example, in costminimization models the impact of interventions on human resources are oftenomitted; hence, different results cannot be explained through such models. The third phase is that of theory testing, which permits the modification anddevelopment both of concepts and of the model. In the field of OM, especially inthe past, this phase has often been carried out using simulation. If there is notesting phase, each new explanation will push the field in a new direction andthere is no real, cumulative progress, as in anecdotal literature. Meredith haslikened this to war stories. What theories exist within OM and what type are they? Many theories are ofthe deductive type, that is, mathematically deduced theory, for example, thosein the field of inventory control or scheduling. They are normative and notdescriptive and are not testable through empirical observation. They can onlybe applied concretely in the context of the confines and limits hypothesizedwithin the definition of the models themselves. 8. IJOPMIn recent years efforts have been made to generate OM theories, even though17,7they are still inadequate in terms of what is really required. To cite only threeareas, total quality management, just-in-time and manufacturing strategy,where some efforts have been made to develop theory using empirical researchas well: areas, that is, other than those such as inventory control or scheduling,where models have been constructed and tested from the MS/OR perspective.662Research efforts have been made along both conceptual and empirical linesin the field of TQM. There were, and still are, many questions left unansweredamong which are: the components of total quality and their measurements,relations between these, the impact of different practices on performance,conditions under which various interventions can be applied and their effects.To mention just some of the research in this area: the definition of a frameworkcontaining the dimension of quality and their measures[36], the comparison oftotal quality and management theory[35] and, the effects of total qualityinterventions on performance and competitive advantage[38,48,49]. A lot ofwork also remains to be done in terms of theory-driven empirical research onquality management, but it would seem to us that the way has been openedtowards the construction of models and theories about a phenomenon whichoften, in the past, was only studied through an anecdote-type approach withattention focused on methods and operating techniques. Because of itsinherently interfunctional nature, the issue of TQM has been taken up byvarious management disciplines; for example, Hackman and Wageman[50]have analysed the congruence between TQM practices and behavioural scienceknowledge. In the field of JIT too, research has tried to answer the open questions wherethere are still a lack of models and theories. Questions such as: what are theelements of JIT and under what conditions can it be successfully implemen-ted[51,52]; what is the relationship between JIT and performance[33,34,37]; andwhat relationships are there between JIT and supply policies[53]. Various studies among those cited for TQM and JIT are empirical and haveused surveys as part of their research methods. In these articles the empiricalresearch has been used for theory building, usually in an initial exploratoryphase. In the area of manufacturing strategy too, considerable efforts have beenmade to improve the range of theories available for two common themes: theprocess and the content of a manufacturing strategy. In their recent review ofthis question, Swink and Way[24] found that both the formulation and theimplementation of manufacturing strategy have been the subject of variousconceptual and empirical works. However, the development of strategic types isstill lagging behind from both the theoretical and the empirical standpoint[54].In his study, Voss[40] identified three elements: competing throughmanufacturing (order winners, generic manufacturing strategies), strategicchoices (processes and infrastructure, focus, consistency) and best practices(TQM, WCM, continuous improvement). There are many conceptual typestudies for each of the three elements. 9. Models of manufacturing strategy have been developed from the evidence of Operationscase studies. But there is still a lack of theory development and systematicmanagementempirical research even though both could be very interesting[55-57].research Some of the already existing theories in the area of manufacturing strategyare well known, for example: Hayes and Wheelwrights Four Stages Model,which defines the strategic role of manufacturing within corporate strategy[16],and Skinners Plat Focus Model[58].663 This latter theory takes two variables into account: factory focus andperformance, and includes a prediction, which is that focused factories performbetter than their unfocused counterparts. Taking this theory as an example,Swamidass[43] argued that theories in the OM area are not expressed in such away as to be able to formulate propositions and hypotheses that can be testedempirically. Starting from the concept of the focused factory and using laterstudies which further developed it, Swamidass described the concept and therelationship between the variables and put forward six propositions forempirical investigation. For example, one of these empirically testablepropositions was formulated as: In companies requiring low-cost productionwith complex processes that are capital intensive, without a need for rapidintroduction of new products, without a need for flexibility in output levels,process focus will perform better than product focus. Existing OM theories are, all too often, implicit or difficult for the researcherto articulate[40]. Many concepts and models in OM could be translated intoempirically testable propositions. Empirical studies can be used either fortheory building or to verify theory but both cannot be done in the same study.Theory testing uses data gathered using a structured data collection method,for hypothesis testing. In theory building research, the goal is to explain thesimilarities, if they exist, between different data sets. Obviously, care must betaken that empirical research does not offer an explanation only for the case inquestion. Theory building uses data to enrich/modify the theory, to refine thedefinition and the measurement of the variables and, to look for other variablesthat can be considered and which may influence the phenomena being studied.Research approach and methodsResearch approaches can be classified into two key dimensions[42]. The firstconcerns the approach adopted to generating knowledge which has twoextremes: on the one hand, the deductive approach and, on the other, theinductive approach. The logical/positivist empiricist perspective is in themiddle. The second dimension concerns the source and kind of informationused in the research which has, on one hand, direct observation and, on theother, subjectivism (artificial reconstruction of reality). Meredith et al.[42] wouldplace peoples perceptions of objective reality in the middle. Normative or descriptive analytical modelling which uses artificial methodsto reconstruct objective reality and a deductive approach (and is commonlyused in operations where simulation is used to test the models) can be put at oneextreme corner. Conceptual modelling (taxonomies and categorizations) can be 10. classified as artificial methods but with an inductive approach; whereas casestudies, in which a company or a plant is studied in detail in its natural setting,where direct observation of an objective reality and an inductive approach areadopted, can be put at the other extreme. Usually such case studies are used toprovide examples and, in the earlier stages of research, for describing thephenomena and related variables. Many methods fall into the intermediate category, which is based on peoplesperceptions of objective reality and takes a logical/positivist empiricistapproach. Some of these methods are: structured/unstructured interviewing,historical/archival analysis (sometimes both methods are used together in thesame study) and survey research. Let us try to understand whether there has been any change and progress inOM research by analysing which methods and approaches have been used. When analysing ten journals over the period 1982-1987, Amoako-Gyampahand Meredith[18] found that the most popular research approach was that ofmodel formulation and simulation which was usually directed towards theorytesting: 69 per cent in the published research and 66 per cent in the pipelineresearch as represented by 1986/87 DSI conference proceedings. They foundthat the proportion of case studies and surveys being used in pipeline researchwas almost twice that used in journal publications. We analysed the papers of the 1996 DSI conference proceedings and theresearch methods used. We then compared these with the figures from ten yearsearlier (see Table II). As the table illustrates, there was a fall-off in the numberof studies based on modelling and simulation, from 66 per cent to 43.8 per cent.Research approachPipeline research 1986/87Pipeline research 1996Modelling33.9627.66Simulation 32.0816.17Survey 13.2126.81Case study7.54 2.13Table II. Field study 1.89 5.53Research approaches Laboratory experimentation1.89 0.85in DSI proceedingsTheoretical/conceptual9.4320.851986/87 and 1996Total 100.00 100.00This drop was matched by an increase in the number of studies of a conceptualand theoretical nature and by more empirical research, particularly that basedon surveys. The proportion of conceptual and theoretical studies doubled, increasingfrom 9.43 per cent to 20.85 per cent. These studies concentrated on three topics:process design/technology (22.4 per cent), quality (20.4 per cent) and strategy(14.3 per cent). The number of studies which used surveys also doubled, (from13.21 per cent to 26.81 per cent). More than half of the surveys concentrated on 11. the topic of quality (34.9 per cent) and strategy (20.6 per cent). With few Operationsexceptions, all surveys were cross-sectional.management Voss[40] highlighted another important change that has taken place over theresearchpast decade. He found that there were differences between the US and theUK/European environment both in the type of research and in the approach toresearch. He compared papers published in the Journal of OperationsManagement, which carries mainly US research, and the International Journal 665of Operations & Production Management, which is an important expression ofthe work carried out by UK and European OM researchers. When ranked bytype of research, Voss found that US publications are dominated by modellingand simulation while UK research is dominated by conceptual, field and survey-based research. The data highlighted in Table II, concerning trends inapproaches found in pipeline research in the USA would seem to show that USmethods are coming closer to those adopted in the UK and Europe, where, inrelation to modelling and simulation, more emphasis is laid on conceptualstudies and on empirical research based on surveys.Survey researchThe term survey is usually used to mean a collection of data, information andopinions of a large group of units, referred to as a population. The subjectstudied (unit of analysis) may be individuals, groups, plant, companies or, even,projects and systems. Surveys use structured and pre-defined questions anddata collection on the sample and can be carried out in a variety of ways: mailquestionnaire, face to face structured interview and questionnaire and/or,telephone interview. Studies are usually cross-sectional, in part because theserequire fewer resources than the longitudinal type. However, if data arecollected at only one point in time, then there are limits to the causal analysisthat can be carried out. Survey research can have three aims[59]: (1) Investigation in order to determine which concepts are related to the phenomena and, how to measure them or how to discover new dimensions of the phenomena themselves. This type of survey can provide the basis for a more in-depth survey. Most of the above- mentioned research on the TQM, JIT and manufacturing strategy topics falls into this category; (2) Confirmatory, in order to test theory, to seek the relationship and/or causal relations between variables. Hypotheses must be very clearly formulated for this type of research, sampling procedures and data collection must be carefully defined. In this case longitudinal studies are more useful. Very little OM research falls into this category; (3) Description of events or opinions and/or their distribution. Unlike in other types of study, here, the aim is not that of testing, or building, a theory. Traditionally, most surveys in OM have been used for descriptive purposes. 12. IJOPM The survey offers a particularly interesting method for empirical studies in OM.17,7OM is a relatively new discipline and there is still more need to build theorythan to test it. Hence, the fact that OM surveys are often carried out on smallsamples is not so serious because large samples are required for theory testingsince, for theory building, one only has to describe and explain the phenomenaand identify the concepts and the relationships between variables. Surveys can666 be very helpful for bringing models, theories, concepts and variables into betterfocus. Theory building research seeks to explain why and how similarities exist indifferent contexts and various surveys which can be repeated in differentsituations would seem to be very useful. One methodological problem which represents an obstacle both to the spreadof survey research and to comparisons between different studies is the limitedavailability of accurate and standardized measures for the concepts that are tobe analysed. If each researcher adopts his/her own measure for a concept, thenit becomes difficult to understand what the validity of these constructs is andimpossible, or nearly so, to repeat the study and compare the results. Hence, oneof the fundamental characteristics for the development of scientific researchwithin a discipline is missing: the creation of a stock of methods and measuresand shared parameters that can be used in different studies. Measures have only just begun to be constructed in the field of OM and thescientific community must make further efforts if it is to have valid and reliableones available so as to ensure that empirical research will be reproducible.However, other important aspects of designing and conducting surveys (e.g.strategy contact, data collection, sample design, methods for data analysis)could benefit from the patrimony of knowledge and methods already availablewithin the social sciences. This measurement problem was highlighted, in relation to managerialdisciplines, in the 1993 Special Research Forum on Methodological Issues inManagement Research. Introducing the articles from the forum in the Academyof Management Journal, Bartunek, Bobco and Venkatraman said[60]: It isdifficult to make new methodological contributions. There are a large number ofcomponents to attend to, such as defining and measuring constructs, linkinghypotheses and testing procedures and, adequately discussing the reliabilityand validity of the measures employed. The papers published in this special issue have been written by OMresearchers experienced in the use of surveys, and offer examples of severalmethodological aspects linked to survey research: measurement, theorydevelopment, combined survey and interview and, use of survey in internationalstudy with transnational comparisons for benchmarking.Some final considerationsMany researchers have stressed the need to develop empirical research, inparticular that which uses surveys, in order to support theory development.However, for this to be successful, diverse approaches must be combined and 13. integrated because empirical research risks becoming an end in itself if it is not Operationsaccompanied by, and does not interact with, other, theoretical and conceptual managementstudies. research To encourage the development of empirical research in OM, various aspectsshould be borne in mind, some of which are described below:many concepts, models and prescriptive ideas present in the OM667 literature should be re-examined in order to extract propositions and preliminary theories that could be used in explorative empirical studies;more attention should be paid to the semantics of the discipline. Use of more than one term to describe the same variable and phenomenon should be avoided, as should lack of clarity, or vagueness, in the terms themselves;concepts and reliable and valid measures should be developed within the field of Operations Management. Particular attention should be paid to the external validity of the instruments so as to ensure greater validity for the results obtained by the survey which has used them;research should be developed within a broader perspective so as to take into account the multiplicity of variables that intervene in operations. One would hope that there could be more contact, and integration with other disciplines, such as both organizational behaviour, in order to take more account of the internal environment in relation to human resources and, industrial organization, in order to consider the external variables of the business environment. As stated above, there has been a gradual increase in the number of interfunctional papers, with a broader outlook, being published;the scientific community should be encouraged to appreciate the value and usefulness of empirical research carried out using existing data collection methods and statistical analysis techniques. Authoritative encouragement, such as the calls for papers which use empirical field- based methodologies which have appeared in some leading journals in recent years, could help a great deal in this. We have seen how there are more papers now, than in the past, which discuss OM research problems and methods;more attention should be paid to explaining the phenomena being observed: to do this methods for analysing causal relationships between variables should be encouraged; furthermore, longitudinal studies should be more widely used;more attention should be dedicated to comparisons between studies and the accumulation of knowledge. 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