Process Management Models in Service Enterprises: A Systematic Literature Review

Improvements to business processes influence the quality of services with which the customer is provided. This principle is the basis of the Total Quality Management approach. This paper presents a systematic literature review carried out in order to identify the most commonly used models in service companies to manage their internal processes. In addition, the type/size of companies that most frequently use these models are identified to find gaps in such utilization to contribute to the service science field. The review process made it possible to identify 1507 studies, 74 of which were eventually classified as primary studies. The results showed that the most widely used models are the European Foundation for Quality Management (EFQM) for organisational management, and the Capability Maturity Model Integration for Services (CMMI-SVC), which is employed to determine the organisation's maturity, evaluate processes and improve services. The use of ISO/IEC 20000 standards for IT service management and ISO/IEC 9001 for product and service quality management was also identified, as were proposals such as the ITIL framework with best practices in IT service management. With regard to the type of organisations that implement these solutions, large companies prevail and small and medium-sized enterprises (SMEs) are underrepresented.


Introduction
Improvements to internal processes influence the quality of the services that industrial and service companies offer to customers [1], [2]. This principle is the basis of the Total Quality Management (TQM) approach [3], and it would appear to be commonly accepted that the quality of internal processes influences and is a key collaborator in external services [4]. Some of the frequent consequences of the bad quality of internal processes as the result of a lack of organisational practices and standardised procedures and processes are delays in the execution of tasks, the inadequate management of staff, etc.
The service sector is particularly influenced by the continuous dynamism that promotes the accelerated expansion of the market and technological advances. This rapid evolution forces organisations to be in a position to be able to adapt to these changes, designing services analysing and understanding consumer needs, measuring the performance of services, optimizing service performance, etc. are particularly important to advance in the services field [5]. Business processes should be managed efficiently in order to improve the quality of the services offered to customers [6]. Strategies related to business excellence, whose objective is to provide guidelines and organisational management criteria as a basis for continual improvement, have consequently emerged from the business world and the scientific sphere. These strategies force companies to reconsider the way in which they are organised and managed, with quality and innovation becoming key elements in the business philosophy. These guidelines may appear in the form of standards and/or models that can be implemented by organisations in order to manage their processes [7] and allow companies to provide products and services that satisfy consumer needs [8]. The processes that intervene in the company's activities should be detailed using a reference model [9]. It is also important to measure the degree to which the processes satisfy the company's objectives and to know what level it is at, which is done by employing a maturity model [10]. Moreover, discovering the level of organisational maturity through the use of an evaluation model makes it possible to detect the organisation's weak points and work to improve them [11].
Several systematic literature reviews dealing with maturity models and their implementation in organisations going through a digital transformation currently exist [12]. Others focus on the ISO 9001 standard and its relationship with organisational output [13]. There are also reviews concerning the history of the management of the quality and classification of models and methods [14], or the difference between the maturity and capacity of business processes [15], etc.
However, at the time of writing this article, systematic reviews that summarize the models most used by companies, in the service sector, to manage their internal processes were not found. The objective of the present paper is, therefore, to fill this gap by presenting a systematic review of the scientific studies in this field in order to detect any omissions and to serve as a basis for future research. In addition, in order to contribute to the field of service science and serve as a basis for future research, this work has the goal of identifying the most used models, know the type / size of companies that use these models and pinpoint the sectors where the models are most used.
This systematic literature review was carried out by following the guidelines provided by Kitchenham [16], which were originally developed for software engineering. The protocol proposed by Biolchini [17] was also considered in order to propose a series of consecutive steps grouped in three phases. These are: Planning, during which the need to carry out the review is identified, and in which the research questions, search string, research sources, inclusion and exclusion criteria and study quality evaluation protocol are defined; Execution of the review, during which the primary studies are selected and relevant data are extracted from them, and finally, the Analysis and discussion of the results phase, during which the results of the review are published.
This work is structured as follows: Section 2 provides details of the methodology employed, while Section 3 shows and discusses the results obtained. Finally, the authors' conclusions and future work are shown in Section 4.

Planning
The objective of carrying out the systematic literature review was defined in this phase. This consisted of identifying the different models employed by service sector companies through which manage their internal processes. The type/size of the companies that most frequently use them was also identified.
In order to achieve the aforementioned objective, it was necessary to define the research questions (RQs) that would guide the systematic literature review process and that would be dealt with throughout the research:

RQ1: Which models or standards do organisations use for the management and quality of their services?
The objective of this question is to discover the existing regulations and models currently employed by service companies in order to improve the quality of their services.
RQ2: In which sectors are these proposals applied? The response to this RQ made it possible to attain knowledge regarding the market sectors in the service industry in which the proposals identified are implemented.
RQ3: What types of companies apply these proposals? The objective here was to identify the size of the organisations that are currently working with models and/or regulations in order to improve the quality of their services.
RQ4: On which of the organisation's spheres are these proposals focused? The aim of this RQ was to discover on which spheres (processes, people, services, etc.) the organisation focuses in order to improve the quality of its services.
RQ5: In which type of model are these proposals framed? Several models and standards can be used to manage an organisation's processes [11]. This question sought to classify the proposals according to their type: reference, maturity, validation, evaluation or improvement. It also served to discover the models and standards most frequently employed and the sectors in which they are applied.
The search string was created by considering key words connected to the business process models utilised in the sphere of services. These key words were then combined with the Boolean operators AND and OR, and the resulting search string was employed in order to search for papers and was formatted according to the specific syntax of each search engine employed. The search string used was the following:

("maturity model" OR "reference model" OR "assessment model" OR "excellence model" OR "process improvement model") AND ("service"),
and was executed in the following databases: WebOfScience, ACM Digital Library, Scopus, EBSCO, IEEE Xplore, Google Scholar and Science Direct.
When processing the search for documents in the electronic databases, categories related to "electronics, electricity and service technologies" were not employed, since they had no direct relation with the topic of interest in this work. Studies focused on software development or the creation of products and/or manufacturing were also excluded, as were those that were principally focused on service technologies (e-services, web services, mobile services, etc.). When selecting papers, we included those written in English that evidenced the use of models for process and service sector management and/or to improve the quality of external services. Papers in which the sphere of application was the service sector were also included.
It was considered important to evaluate the quality of each of the papers [18] with regard to the objectives of this work. This led to the definition of Quality Assessment questions (QAs), which were employed in order to provide the studies with scores. The responses to each QA could attain the following values: 0 = (N) Not fulfilled, 0.5 = (P), partially fulfilled and 1 = (S) Fulfilled.
The QAs and their possible scores are: -QA1. Is the objective of the research clearly defined? Yes (1), the study has clearly defined objectives. Partial (0.5), the objectives are defined, but not clearly. No (0), the objectives of the work are not defined.
-QA2. Is the research work coherent? Yes (1), the work developed is coherent with the proposed objective. Partial (0.5), there is little coherence between the objectives and the work developed. No (0), there is no coherence between the objectives and the work developed.
-QA3. Is the research process or method clearly defined? Yes (1), the study clearly defines the methodology used. Partial (0.5), the study employs a methodology but it is not clearly defined. No (0), the study does not provide a definition of the research methodology employed.  (1), the study is validated in a real environment. Partial (0.5), the study is partially validated in a real environment and partially validated in a conceptual environment. No (0), the study is not validated using a real case.
-QA5. Are the limitations of the work clearly documented? Yes (1), the limitations of the study are clearly defined. Partial (0.5), the limitations of the study are not clearly defined. No (0), the limitations of the study are not defined.
-QA6. Does the study contain relevant quality references? Yes (1), the study contains relevant references that are recognised and/or related to process management in organisations. Partial (0.5), the study references some relevant sources. No (0), the study does not reference any recognised, relevant or quality sources.

Carrying out the Review
Each of the data sources listed in Section 2.1 was searched using the search string shown in the same subsection. This led to the attainment of the 1507 initial documents shown in Table  1 in the "Found" column. This list was then refined by eliminating repeated studies, which led to the attainment of the 1052 studies as shown in the column entitled "Not repeated" in Table  1. Each study was subsequently verified according to the inclusion criteria (138 relevant studies), after which it was necessary to verify whether or not they fulfilled any of the exclusion criteria. This resulted in 74 primary papers, representing 54% of the relevant studies. The primary studies were then enumerated (see Table 2), after which the process of extracting and analysing the data contained in them began. This was done using the Mendeley computing tool in order to extract information such as: title, authors, year of publication, country of publication, DOI, type of work (journal or conference), and the conclusions and abstract of each paper [18].
In order to respond to each of the RQs (defined in Section 2.1), a table in which to gather together the relevant information was created, after which the process of extracting and analysing the data contained in the primary studies (Table 2) began. As will be noted in Table  1, 28% of the primary studies were obtained from the WebOfScience database, while 22% were from Scopus, 16% were from IEEE Xplore, 11% were from EBSCO, 9% were found in both Science Direct and ACM Digital Library, and 4% were from Google Scholar.

Analysis and Discussion of Results
Each quality assessment question (QA) was evaluated, and each study was awarded only one of the values shown in Section 2.1. The maximum possible weighting for each QA is 6. Of the 74 primary studies analysed, 86% attained a score of 3 or more. The total weighting of the studies according to the QAs is shown in Table 3 These data make it possible to state that the quality of the studies analysed is very good, since they all attained mean values for the areas studied. That is to say, the objectives of the studies analysed are clearly defined, there is coherence between the development of the work and its objective, the methodology employed is clearly defined and has been validated, the limitations are defined and the bibliographic references are relevant.

RQ1:
The models most frequently employed are EFQM, which focuses on the organisation in general [93], CMMI-SVC and CMMI, which focus on service quality improvement processes [92], and the Information Technology Infrastructure Library (ITIL), which comprises good practice guidelines for the management of information technology (IT) services [94]. With regard to regulations, there are the ISO/IEC 20000 standards for IT service management [95] and the ISO/IEC 9001, which is used to improve product and service quality [96].
RQ2: The most representative sectors in which the proposals identified are applied are principally IT and Health, followed by Banking, the Commercial sector and the Industrial and Software Development sectors (Fig. 1). With regard to the IT sector, there are studies that describe a model focused on the evaluation of IT processes [24], methods that can be used to apply ITIL on the basis of the business process management lifecycle [31], an analysis of models applied in the IT industry [62], etc. In the case of the Health sector, there are studies dealing with the management of projects and maturity models [28], support models for consensus through the use of EFQM based on linguistic information [33], etc.  Fig. 2 shows that more than 50% of the entities that use the proposals identified are large companies, while only 9% are small and medium-sized enterprises. The fact that SMEs barely employ process management models can be attributed principally to the economic, technological, human resources, etc. required by these proposals for their application [97].  RQ5: This analysis revealed that the proposals are not exclusive, i.e. they can be framed within more than one type. For example, the analysis revealed that the CMMI model fits into the maturity, evaluation and improvement model (Fig. 3). It is also possible to appreciate the variety and type of proposals implemented by service companies, since these proposals can be classified as regulations, methodologies, models, capacity, reference, maturity, evaluation, excellence and improvement models, and may, moreover, be oriented towards IT and non-IT services and/or general services (It and non-IT).

Conclusions and Future Work
The systematic literature review presented herein was carried out with the objective to identify models most used by companies through which manage their internal processes, identifying the type/size of companies that use them most frequently and discover gaps in the use of models in order to contribute to the services science field. Following the guidelines defined by Kitchenham [16] and the protocol proposed by Biolchini [17], 1507 documents initially were found and 74 were selected as primary studies for their subsequent analysis. The results obtained made it possible to discover that the models most frequently employed are the EFQM, CMMI-SVC, CMMI and ITIL. The most frequently employed standars are, meanwhile, the ISO/IEC 20000 and ISO/IEC 9001.
Regarding to the gaps detected, it was identified that small and medium-sized enterprises (SMEs) in the service sector which wish to manage their internal processes through models, are highly unrepresented. Only 9% of the studies analysed consider SMEs, while more than 50% are oriented towards and applied in large companies. Moreover, the majority of the proposals are focused on IT, software development and telecommunications services.
It is for this reason that as the future work is related to considering the possibility of proposing an internal processes management framework that will be oriented to small and medium-sized service companies.