Maritime University of Szczecin
Akademia Morska w Szczecinie
2010, 24(96) pp. 111–117 2010, 24(96) s. 111–117
Syntax errors in the EPC diagrams of the integrated
management system documents
Błędy składniowe w diagramach EPC w dokumentacji
zintegrowanych systemów zarządzania
Bartosz Szczęśniak
Silesian University of Technology, Faculty of Organisation and Management Institute of Production Engineering
Politechnika Śląska w Gliwicach, Wydział Organizacji i Zarządzania, Instytut Inżynierii Produkcji 41-800 Zabrze, ul. Roosevelta 26, e-mail: bartosz.szczesniak@polsl.pl
Key words: procedure creation, process modelling, EPC models Abstract
The EPC methodology enables accurate modelling of economic processes. One of the main spheres of its application is procedure creation under quality, occupational health and safety or environment management systems. The development of the methodology in question has led to establishment of precise conditions that must be conformed with in a correct process model. The main theme of the article is a general discussion of the EPC methodology. Based on an analysis of numerous literary studies published, a set of principles that should be met by an EPC diagram as a graphical representation of the process being described has been identified and discussed. Another subject touched upon in the article is the results of examinations of 156 diagrams from documents of integrated management systems implemented in two companies. The examinations conducted have implied that the diagrams created in the course of the documentation drawing up do not conform with many of the applicable requirements. The individual syntax errors occurring in the documents have been identified and discussed in the paper, and special attention has been paid to those related to application of the OR and XOR split connectors as well as those occurring when joining diagrams. Słowa kluczowe: tworzenie procedur, modelowanie procesów, modele EPC
Abstrakt
Metodologia EPC pozwala na precyzyjne modelowanie procesów gospodarczych. Wśród wielu obszarów jej zastosowania znajduje się miedzy innymi tworzenie procedur w ramach systemu zarządzania jakością, bez-pieczeństwem i higieną pracy czy środowiskiem. W ramach rozwoju metodologii określone zostały precyzyj-ne zasady, które muszą być spełnioprecyzyj-ne przez prawidłowy model procesu. W artykule omówiono ogólnie meto-dologię EPC. Na podstawie badań literaturowych zidentyfikowano i przedstawiono zbiór reguł, które powin-ny być spełnione przez diagram EPC będący graficzną prezentacją opisywanego procesu. Przedstawiono również wyniki badań przeprowadzonych na 156 diagramach pochodzących z dokumentacji zintegrowanych systemów zarządzania z dwóch firm. W wyniku badań stwierdzono, że tworzone w ramach dokumentacji diagramy nie spełniają wielu z przedstawionych zasad. Zidentyfikowano i omówiono pojawiające się w dokumentacji poszczególne błędy składniowe. Za szczególnie istotne uznano błędy związane ze stosowa-niem operatorów rozdzielających OR i XOR oraz błędy pojawiające się w zakresie łączenia diagramów.
Introduction
In the process of documenting a quality management system conforming with the ISO 9000 standards, an environment management system conforming with ISO 14000 as well as an
occupational health and safety management system conforming with PN-N 18000, there are procedures being created to describe the manner of performing the individual activities in a company. Under these procedures, the course of a process being described can be provided in a descriptive form as a plain
text. However, such a solution seems not transparent enough. In order to understand exactly how the individual activities are interlinked, it is necessary to invest a lot of energy and time. Low transparency of such a solution leads to a situation that the errors occurring in the process description are often very difficult to notice. Therefore, while developing procedures, besides the textual description, graphical methods are used to depict the appropriate manner of behaviour. The most common of such methods applied in the procedures is visualisation of the process chain by means of a classic block diagram. Sometimes, however, due to the fact that certain dedicated IT tools supporting the procedure creation process and the subsequent documentation administration are used, the most applicable methods are those used for the sake of the economic process modelling, one of which is the EPC modelling method. The methodology in question was created and is currently being developed under the programme of collaboration between the scholars of the Institute for Economic Information Science in Saarbrücken and the SAP AG company. The actual authors of the method are claimed to be G. Keller, M. Nűttgens and A.W. Scheer. Its first study was published in 1992 [1]. It contained various principles of creating process models by application of events and functions taking place alternately. However, the principles proposed were of informal nature. The works leading to the actual formalisation of the principles were undertaken by W. van der Alst, M. Nüttgens and F.J. Rump. W. van der Alst who managed to publish a formal description of the EPC models in 1999 [2]. The principles they proposed applied to individual models only. The formalised principles applicable to individual models as well as the principles of creating more complex structures as a result of joining models were published by M. Nüttgens and F.J. Rump in 2002 [3]. In the years to come, many authors proposed their own formal rules of creating EPC models. The actual guidelines to their syntax can be found in numerous studies including those of V. Gruhn, R. Laue, J. Mendling, E Kindler or N. Cuntz [4, 5, 6, 7, 8]. Besides the problems of syntax, authors of many publications focus on the subject of semantics applicable to the methodology in question [3, 4, 5, 6]. The problem of the economic processes modelling using the EPC models has also been widely discussed in the Polish literature. The general rules of their creation were provided in the studies by R. Gabryelczyk and M. Lasek [9, 10].
Currently, the methodology of describing pro-cesses by means of the EPC models finds common
application in numerous spheres of a company activity the most important of which are [11]: process analysis,
accounting of operating costs, simulation,
process documenting, risk management, work flow management, knowledge management, quality management.
Using the aforementioned models involves application of the appropriate IT solutions. Undoubtedly, the most commonly applied and advanced tools supporting this technology are the solutions delivered by IDS Scheer. They constitute a group of solutions integrated around the ARIS platform which, while being constantly developed and improved for many years now, ensures support for the decided majority of the concepts of the EPC models application. One of the spheres of applica-tion of the concepts discussed is creaapplica-tion and sub-sequent administration of the documentation for the systems of quality, environment or occupational health and safety management. For the sake of crea-tion of the procedures describing the course of the individual processes, tools such as ARIS Easy Design or ARIS Toolset can be used for the model-ling. For publication of the documents drawn up, tools like ARIS Process Portal or ARIS Business Publisher can be used. In Poland, some of the tools frequently used for creation and administration of the management system documentation are the solutions delivered by DGA S.A. In this case, the models are created in DGA Process, and the docu-ments are published by means of DGA Quality. Using the aforementioned solutions entails nume-rous advantages the most important of which are definitely the possibility of transparently and precisely reviewing the given process, providing the company employees with easy access to the documentation being developed as well as to the documents used in the processes, and ensuring support for the processes of the documentation amending. Another significant advantage of those solutions is also the option of using the models created for the management system documentation purposes under future projects. It is a common situation that implementation of, for instance, a quality management system is treated as the means to put the organisation in order before a comprehensive IT system is implemented, e.g. the ERP, CRM or workflow system [12]. Unfortu-nately, one can easily notice that in spite of having established very precise and clear rules of the EPC
models creation, there are still syntax errors occur-ring in the documentation developed. The main purpose of the models prepared under the manage-ment system documanage-mentation itself is the visualisa-tion as well as transparent communicavisualisa-tion of the course of the given process to the employees reading the procedures. The fact that the errors occur may cause doubts of the persons well aware of the principles relevant to the methodology being applied. In other spheres in which the methods in question are used, occurrence of the syntax errors can even make the models created useless. In the following sections of the article, based on the analysis of the literary references, the principles which should be adhered to when creating the EPC diagrams have been discussed. The author has also presented various kinds of syntax errors identified in the diagrams examined under the documentation of the quality and environment management sys-tems analysed.
EPC models
Based on the publications referred to in the introduction, one can indicate the main features of the EPC models. In order to create a model of the given economic process, it is to be represented as a set of events and functions taking place alter-nately. The functions determine the actions to be performed under the process. The events apply to the individual states of the process. Most com-monly, they are simply statements that something has happened. They are usually represented as sen-tences relating to the past. The examples of events can be as follows: “the audit plan was approved” or “the time has come to prepare the budget”. Unlike the events, the functions are usually formed as commands in the imperative. The examples of functions can be: “prepare the audit plan” or “pre-pare the technical documentation”. Besides the functions and events, at the beginning or the end of the EPC model, there can be a process interface. This element is a reference to the process model which is to be implemented before or after the cur-rent one. The fact of having the process interface at the model beginning implies that the current process is performed after the end of the preceding one. The fact of having the process interface at the model end implies that the current process is followed by another one. The name assigned to the process interface is the name of the model it refers to. Using the process interface is one of the methods of joining the EPC models. This method is applied when the models are related to the processes performed in a specific sequence. Another case of joining processes is when one of
the functions of the given process is to be expanded by means of another EPC model. In such a case, the joining is done using the function being expanded. The models linked with another models by means of the process interface or a function are called hierarchical. The models containing no such inter-faces are known as flat.
At the beginning of each model, there must be an event or a process interface. When the model begins with an event, it determines a situation after which the process is to be performed and it is called the starting event. Also at the end of each model, there must be a process interface or an event which, in this case, is known as the final event. In order to represent the process chain, functions, events and process interfaces can be connected directly or by means of connectors OR, XOR and AND. Each of these connectors can function as a split or join connector. The split connectors are used to divide the course of the process into several paths. The join connectors are used to join several paths into one. When the AND split connector is used in the process, all the functions following it are to be performed or all the events following it are to happen. When this connector is used as a join connector, the process can be continued when all the events preceding it take place or when all the functions preceding it are accomplished. When the XOR split connector is used, after the connector in the process, only one of the events following it is actually to take place. When this connector is the join connector, the process will be continued when exactly one of the events preceding it takes place or when exactly one of the functions preceding it is performed. When the OR split connector is used in the process, at least one of the events following it is to happen. When the OR connector is used as the joining one, the process will be continued when at least one of the events preceding it takes place or when at least one of the functions preceding it is performed. Among all the applications of the connectors, the most restrictive rules are in effect when split connector OR and XOR are used. In both cases, the elements following the connectors cannot be functions. They can only be events. The basic EPC models represent the process chain. In order to have the information on additional significant elements related to the economic process being described included, one applies the eEPC models expanding the basic concepts of the EPC models. These models, besides the afore-mentioned elements, also use elements related to the organisational structure and to the documents drawn up and used in the process. The EPC models in the graphical form are depicted by means of the
relevant EPC diagrams. These diagrams are based on the symbols presented in figure 1 and connected with the arrows indicating the process chain. For the sake of graphical representation of the process being modelled, also “office process” diagrams are used. In these diagrams, different, more employee- -friendly graphical symbols are used, however, the general principles governing them remain the same as in the EPC diagrams.
Fig. 1. Basic symbols used in the EPC diagrams
Rys. 1. Podstawowe symbole stosowane w diagramach EPC
Based on the formalised principles of the EPC model syntax, one can establish specific rules that must be complied with by an EPC diagram:
1) All components of the EPC diagram are inter-linked by means of arrows.
2) The components cannot be linked with more than one arrow.
3) None of the components can be linked with an arrow with itself.
4) Functions have exactly one incoming and one outgoing arrow.
5) Events can have:
a) exactly one incoming and one outgoing arrow,
b) only one outgoing arrow (starting event), c) only one incoming arrow (final event). 6) Process interfaces can have exactly one
in-coming or one outgoing arrow.
7) The diagram must be provided with at least one starting event or at least one process interface with one outgoing arrow. There must also be at least one final event or at least one process interface with one outgoing arrow.
8) Functions can only be linked to events with ar-rows.
9) Process interfaces can only be linked to events with arrows.
10) Events can only be linked to functions or proc-ess interfaces with arrows.
11) The links referred to in items 6–10 can be established directly or indirectly by means of connectors.
12) The connectors can have:
a) one incoming arrow and several outgoing arrows (such connectors are known as the split connectors),
b) several incoming arrows and one outgoing arrow (such connectors are known as the join connectors).
13) The diagram can have no loop consisting of connectors only.
14) Neither split connector OR or split connector XOR can be used after an event.
15) A function can be linked with one EPC diagram at maximum.
16) Each process interface must be linked with exactly one EPC diagram.
If the successive EPC diagram is linked with the current one by means of a function, then: vall the events preceding the given function constitute a set which corresponds to the set of starting events of the EPC diagram linked,
all the events following the given function constitute a set which corresponds to the set of final events of the EPC diagram linked. 17) If the successive EPC diagram (B) is linked
with the current EPC diagram (A) by means of the process interface, then all the events pre-ceding the process interface in diagram A which points to diagram B take place after the process interface in diagram B which points to diagram A.
18) As a result of a series of links between the indi-vidual diagrams, the given EPC diagram must not be linked with itself.
Syntax errors in the diagrams examined
In the course of the examinations conducted on the diagrams from documents of the integrated management systems of two companies, it was revealed that, in some cases, they were not con-forming with the aforementioned syntax rules. The most frequent nonconformity was the occurrence of the subsequent functions directly after one another or their being split with only the connector without the required event to split them. In the group of 156 diagrams examined, this type of nonconformity was found in as many as 140. A similar error was putting two events one after another and the occurrence of a process interface after a function and a function after a process interface. These kinds of syntax errors have been shown in figure 2.
In the documents subject to examinations, there were 19 diagrams containing errors of an event following an event, a process interface occurred directly after a function in 7 diagrams and a func-tion was placed directly after a process interface in 5 cases. Two functions or two events occurring after each other, unless this error involves non-observance of some of the other syntax rules, seem not to pose a serious problem to the process under-standing. However, this is not the case when there
event function conne
s process
are functions and a process interface occurring after each other. If one is to observe the principle that there must be an event between a function and an interface, in each path of the process before the first function and after the last one, there must be an event explicitly identifying the state in which the process is to be initiated as well as the state in which it is to be concluded. If a process is finalised with a process interface directly following a func-tion, there is no information on the final state included in the diagram. If there is an interface connected with a function at the process beginning, the diagram contains no information on the event that must take place for the process to be per-formed. A similar effect is obtained when one of the EPC diagram paths is not finished with an event. However, this type of error was rather
seldom, as it was encountered in only two of the diagrams being analysed. In one case, it caused the lack of any final event in the diagram, being a situation which occurred three times in total in the materials examined. In one case, the error was related to concluding all the process paths with a function, and in two other cases, there was a loop-ing in the process causloop-ing the diagram developed to lack any ending. This kind of error has been depicted in figure 3. In process 1, the lack of a final event is due to the fact that the path ends with a function, and in process 2, the missing event is an effect of the process looping.
Another error found in the diagrams being examined was the occurrence of a function or a process interface after split connector OR or split connector XOR. In both cases, after the connectors, there should be an event to determine the situation in which the given process path is to be taken. If there is no such event, one cannot correctly un-derstand the process logic where the paths split. The lack of an event after split connector OR was revealed in 4 cases, and the same happened for split connector XOR in 17 of the diagrams analysed. This error has been shown in figure 4.
The interesting peculiarity is that this kind of error always occurred in relation to the error of using functions or a function and a process interface after each other. Despite having revealed the error of using split connector XOR or OR directly after an event in 4 diagrams, the error of inappropriate placement of a component after the connector was not revealed in any of them, even though it should have occurred bearing in mind the principle of alternate placement of the individual components. Consequently, one could notice that although the very error depicted in figure 1, related to using functions or a function and a process interface directly after each other, does not interfere with the actual message of the process to a large extent, it could contribute to the occurrence of other errors which may distort the message far more seriously. Distortion of the process logic is also the case when there is more than one arrow coming to or going out of such diagram components as functions, i.e. when the same components are
F2
F1 F1 F2 PL1 PL1 PL1 PL1
Fig. 4. Syntax error consisting in placing a function or a process interface after split connector XOR or OR
Rys. 4. Błąd składniowy polegający na wystąpieniu funkcji lub łącznika procesów po operatorze rozdzielającym XOR lub OR
E1 F1 PL1
E2 F2 F1 PL1
F1
Fig. 2. Syntax errors of placing functions and events after one another, placing functions after process interfaces and process interfaces after functions
Rys. 2. Błędy składniowe polegające na występowaniu po sobie funkcji, zdarzeń, funkcji po łącznikach oraz łączników po funkcjach E1 F1 E2 F2 E1 F1 E2 Process 1 Process 2
Fig. 3. Syntax error of a missing final event
Rys. 3. Błąd składniowy polegający na braku zdarzenia koń-czącego
linked with more than one preceding component or more than one subsequent component. In such a case, the logic of splitting and joining the process is completely missing. In the materials being examined, this kind of error occurred in 7 diagrams for functions, in 10 diagrams for events and in 6 diagrams for process interfaces. The last error identified in the scope of creating single EPC diagrams was the application of a connector as a join connector and simultaneously as the split connector. This error, however, does not distort the information on the process course to much, and it was revealed in 5 diagrams.
Another group of errors is related to joining EPC diagrams. In this case, the first kind of error is the non-compliance between the events occurring before and after the process interfaces in the interlinked diagrams. This was the case in the situation depicted in figure 5.
Fig. 5. Syntax error of non-compliance between the events occurring before and after the process interfaces in the inter-linked diagrams
Rys. 5. Błąd składniowy polegający na braku zgodności po-między zdarzeniami występującymi przed i po łącznikach procesów w połączonych diagramach
By observing the principles of joining diagrams, one can create a single flat diagram based on a set of hierarchical ones [3] which is impossible if the aforementioned error occurs. Such a problem was found in 23 pairs, i.e. in 46 joined diagrams. In the group being analysed, there were 95 hierarchical diagrams. This means that the error occurred in as many as 48% of the diagrams examined. Another error leading to merely a seeming joining of diagrams is placement of a process interface in only one of the diagrams. This was the case in the situation depicted in figure 6.
Also in this situation, it was impossible to create one flat diagram from the diagrams joined in such a manner. This error can occur in two variants. The first one is a situation when, in the current diagram, there is a process interface pointing at another
diagram, describing the process, which is to be performed after the end of the current process, and there is no interface pointing at the current diagram in the subsequent one. This variant was charac-teristic of 23 diagrams analysed. The second variant is a situation when there is a process interface pointing at the preceding diagram in the current one, but there is no interface pointing at the current diagram in the preceding one. This variant of the error was identified in 14 diagrams. The last of the errors found was placing a process interface inside the diagram. In such cases, the process interface was treated as a interface pointing at the subsequent diagram and simultaneously as one pointing at the preceding diagram. This error was revealed in 5 diagrams.
Conclusions
The examinations conducted have implied that despite having very precise principles of creating EPC diagrams, there are numerous errors occurring in the diagrams developed for the sake of the documentation of integrated management systems. Bearing in mind the possibility of distorting the actual message of a diagram as well as the incidence of the individual errors, the most significant of them are: using a function after split connectors OR and XOR, joining diagrams without compliance between the events before and after the given process interface, and joining diagrams by means of a process interface placed in only one of the diagrams. Another major error is also joining events, functions or process interfaces with other components using more than one incoming or outgoing arrow. All the errors revealed in the course of the examinations imply the spheres to which one must pay special attention while modelling economic process by application of the
E1 F1 E2 Process 1 Process 2 Process 2 E3 F2 E4 Process 1 E2 ≠ E3 E1 F1 E2 Process 1 Process 2 Process 2 E3 F2 E4 E5 F3 E6 Process 3 E7 F4 E8 Process 3 Process 4
Fig. 6. Application of a process interface in only one of the joined diagrams
Rys. 6. Zastosowanie łącznika procesów po stronie jednego z łączonych diagramów
methodology discussed as well as during the training courses organised in this scope.
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Recenzent: prof. dr hab. inż. Krzysztof Chwesiuk Akademia Morska w Szczecinie
