# Logistics Service Provider Lifecycle Model in Industry 4.0: A Review
## 2 Systematic Literature Review (SLR)  
For two decades, Systematic Literature Reviews (SLR) have been widely used for reviewing the current literature to identify and evaluate the state of the art and present future topics regarding the field of research [41; 42; 43; 44]. SLR further assists researchers in the generation of a systematic contribution based on secondary-data-based findings [15; 39]. The Google Scholar website shows results of more than 300,000 papers based on researchers using SLR [45]. [PERSON] and [PERSON] [46] described a systematic review as \"a specific methodology that locates existing studies, selects and evaluates contributions, analyses and synthesizes data, and reports the evidence in such a way that allows reasonably clear conclusions to be reached about what is and is not known\". The SLR method has been evaluated by studies in the ACM Digital Library, Taylor & Francis, Emerald, Google Scholar, Elsevier, IEEE Xplore, Inform, Springer, and the ISI Web of Science [9; 43; 47]. The quality of SLR has been discussed in various journals, conference proceedings, and book chapters [15; 28; 42; 48]. Thereby, bibliometric reviews are often used as a visualization tool to study research trends and other related fields, regions, and publications, whilst SLR is applied to search and summarize the systematic research area, which can solve specific problems [15]. The SLR process can be separated into five steps: (1) formulation of the research question, (2) identification of studies, (3) selection and evaluation of studies, (4) analysis and synthesis, and (5) reporting of results.  
Step 1: Formulation of the Research Question  
Step 1 is to create the scope of research by formulating the research question and/or problem. The question step can verify the utilization discovered from the systematic review. This step is to define the scope of the research area and set the data collection to find the solutions to problems to formulate a new model. [PERSON] and [PERSON] [46] determined the structure of a systematic review as contexts, interventions, mechanisms, and outcomes.  
Step 2: Identification of Studies  
Locating studies is related to the question and formulated in locating, picking up, and evaluating. This step is for searching for research on databases such as Google Scholar, ACM Digital Library, Emerald, Elsevier, IEEE Xplore, Springer, and Taylor & Francis [28]. The initial search string for the SLR can be formulated as follows: \"(TITLE-ABS-KEY (\"artificial intelligence\" OR \"machine learning\" OR \"deep learning\") AND TITLE-ABS-KEY (\"smart logistics\" OR \"smart production\" OR \"industry4.0\").  
Step 3: Selection and Evaluation of Studies  
The step of study selection and evaluation defines the inclusion and exclusion criteria to search in the pre-defined area. The authors define the inclusion and exclusion criteria based on similar papers in the field of research.  
Step 4: Analysis and Synthesis  
This step discusses the data extracted from the systematic literature review. The papers identified are classified into six categories: survey, interview, case study, content analysis, literature review, and modelling.  
Step 5: Reporting of Results  
The last step shows the results of the SLR and identifies trends in the area of research.