Digitization in maritime logistics — What is there and what is missing?

: The global seaports are of pivotal importance for the world economy. Since 1990, global container traffic has grown by an average of 10% annually. Equally, the steady growth of ship sizes poses major logistical and technical problems worldwide. Given these facts, shipping and maritime logistics would largely benefit from Big Data as well as the emerging digital technologies. Apart from the many positive effects of digitization in maritime logistics with respect to efficiency, safety and energy saving, there are, however, also risks (e.g. data abuse, cyber-crime). Based on a systematic literature review, this article provides an overview of the current state of digitization in maritime logistics, discusses existing problem areas, and shows potential for improvement. The results show that it is essential to capture the development potential in order to be able to benefit from the advantages. However, research is still in its initial stages, and there is a lack of theoretical and empirical work as well as explanatory approaches to appropriate recommendations for action and restructuring.


PUBLIC INTEREST STATEMENT
In maritime logistics, automation and digitization are constantly advancing, which noticeably affects all involved as business models and processes will change dramatically in the coming years. Against the background of the transformation process, this paper analyzes the status quo, discusses existing problem areas and identifies the arising future challenges. Furthermore, it provides recommendations for action in research and practice. A comprehensive and systematic literature analysis equally considering scientific and practical literature serves as a solid basis for this contribution. The results show that it is essential to identify the development potential in order to take full advantage of the opportunities in practice. However, research in this area is still in its initial stages. There is a lack of theoretical and empirical work as well as alternative explanatory approaches for appropriate recommendations for action and restructuring.

Introduction and motivation
Today, more than 90% of the world's goods transport is handled by sea. Every year around 8 million tons of goods are transported across the sea by container ships, tankers, and bulk carriers (Göpfert & B raun, 2008 ). While in 2013 some 9.5 billion tons of sea freight have been loaded at seaports around the world, the total capacity of the global container fleet increased to approximately 20.5 million TEU 1 in 2015 (Grote et al., 2016). Apart from the decline in 2009, which was due to the economic crisis, there has been a steady increase in the global container traffic every year. In view of the ad v ancing global ization as well as the further progress in the containerization of general cargo transport, a further increase in container transport is expected (Fruth, 2016). Compared with the world gross domestic product and the world trade, sea trade has shown twice as fast growth in recent years. Container transport thereby accounts for less than a third, but was the fastest growing market segment within the maritime logistics sector (N.U., 2011). Maritime logistics is thus one of the key sectors for digital transformation. With its high degree of networking and its large number of interfaces, maritime logistics offers a broad range of applications for digital technologies. Therefore, digitization and logistics 4.0 provide a great potential for maritime shipping companies (Binder, 2016c). Traffic, port logistics, and just-in-time shipping will change as an electronic revolution takes shape with Big Data and the increasing networking of technologies (Berg & Hauer, 2015). Already today large amounts of data are gathered on each individual ship, although most of them still remain unused. However, given the multitude of new digital business models, data usage will inevitably change within the coming years (Fruth, 2016). The International Maritime Organization (IMO) supports the introduction of electronic data exchange from ship to ship and from land to ship, to improve the efficiency, safety, and data security of navigation and communication (Berg & Hauer, 2015). For the ports and thus for the digital linking of complete value chains in maritime logistics, there are numerous developments in the area of Global Positioning System (GPS) navigation, more accurate ship arrival times, weather data in real-time feeds, and smart container technology to name only a few of the possibilities. Likewise, there is a mathematical model currently being developed that predicts earlier and more accurately ship arrival times, based on AIS 2 , weather, tide, and maritime traffic data (Kuchta, 2016).
The interaction of all actors in the maritime supply chain as well as the sequence of the related processes is shown in Figure 1. The actors involved include senders, logistics providers (e.g. forwarders, port and terminal operators, and shipping companies) as well as the receivers. Some of the stakeholders (e.g. senders, recipients, shipping agents, traffic control centers, port operators, but also price regulation authorities, banks and transaction brokers) use new ICT (e.g. GPS navigation, electronic seacharts (ECDIS), RFID technologies, AIS and Big Data). In this way, the actors in the maritime transport chain, e.g. terminal operator, ship brokers, tugboats, pilots and forwarders, can bundle and, in case the time of arrival changes, adapt their resources appropriately (Fruth, 2016). Further, all parties concerned, e.g. the terminal operators, can be informed about the loaded goods prior to the ships' docking. Sea containers are equipped with radio-frequency identification (RFID) chips and thus become intelligent containers. Through smart containers and a suitable networking of single information systems, it is possible to fully digitize and globally network the entire maritime transport in order to render transparent the respective processes (Berg & Hauer, 2015). All terminal vehicles, machines and devices that are involved in the transportation, loading and unloading of goods are interconnected and communicate with each other, which is enabled by means of suitable information, communication an d automation technologies. Such an inclusion in higher order systems leads to cyber-physical systems (Bai, Zhang, & Shen, 2010). In the case of forward and hinterland transport, the synchronous modality is based on the idea that the optimal transport mode and route combination can be selected based on real-time information. For example, the transport of smart containers is carried out depending on the respective availability of trucks, railcars, feeder ships 3 or inland waterway vessels. Synchronous modality thus allows significant transport cost reductions and an optimum utilization of transport means while adhering to the respective delivery conditions . Based on the "Internet of Things" concept, machines and equipment on board ships can be equipped with sensors and transmitters that transmit performance data as well as early signs of errors to the ship computer via WiFi so that any necessary repairs or replacements of a defective system can be executed in the home port, which can save time as well as avoid considerable costs of flying technicians and parts to a ship in transit (Berg & Hauer, 2015).
In this paper, we address the following research questions (RQ): RQ 1: What is the current status quo of digitization in maritime logistics? RQ 2: What are the future challenges of digitization in maritime logistics?
To answer these research questions, a systematic literature analysis is carried out in various literature databases and specialist journals with the purpose to equally capture the scientific as well as practical status quo. The contribution at hand is structured as follows: In the second section, conceptual foundations and technologies in the area of digitization in the maritime logistics are discussed in order to obtain a primary basis. The third section describes the methodological approach. In the fourth section, the results of the literature analysis are presented in a concept matrix and recommendations for research and practice are given in a PESTEL matrix. The work concludes in section 5 with a final consideration, as well as implications for science and practice. compared with other companies. In the field of maritime logistics, multimodal transport processes in the ports require an optimal networking of the individual actors who coordinate their activities in the transport chain in order to optimize traffic and goods flows (Berg & Hauer, 2015). With the use of Big Data and digital transformation, the fleet controls can be optimized, whereby costs are reduced and the environmental protection is improved. Traffic control and traffic flows can be optimized by using the ship's operating data, thereby avoiding critical situations and thus reducing the risk of accidents. All ship data, e.g. machine, aggregate, weather and cargo data, are transmitted to the onsh o re manageme nt in real time, who can, if necessary, enter into a direct dialog with the ship's management (Arndt, 2016). The current digital transformation is also regarded critically. Technology and information ethics ask for the gain and loss of personal and informational autonomy and the dependency of the customers on information technology and information companies. Moral and ethical problems arise, especially in the field of technology, information and economic ethics (Bendel, 2015). The digital transformation of maritime logistics is successful if the topics of data protection and data security are given a central role in the implementation strategy. The handling with digital applications and technologies does not only require competent users who are familiar with the digital innovations, but also secure systems that guarantee the protection of the company's internal infrastructure and operating systems from cyberattacks (Schweer & Sahl, 2016).

Research approach
The present research contribution consists of a systematic literature analysis to identify the status quo of digitization in maritime logistics. The systematic literature analysis is employed, since in scientific research it is an adequate means to determine the current state of research (Fettke, 2006). It avoids redundant investigations and leads to important contributions in the corresponding research field. The three essential characteristics of a literature analysis are: systematics, explicitness, and reproducibility. The literature analysis in this article summarizes the research work on digitization in maritime logistics. For the analysis of the relevant literature, we decided on a concept matrix based on the five-step concept described by vom Brocke et al. (cf. Figure 2).  The definition of the investigation framework, the development of a research concept and the literature search with keyword search are described in the section The literature analysis as a survey method: documentation. The analysis and synthesis of the results of the literature analysis are given

Definition of scope of investigation
According to vom Brocke et al., the classification scheme for literature searches, according to Cooper (1988) with six features, is suitable as a tried-and-tested tool and is shown in Figure 3. The highlighted fields illustrate the scope of this paper. The focus lies on the identification of the available literature, shows its degree of coverage, and cites from the identified literature.

Research concept
According to the definition of the scope of the investigation, the search concept has to be explained. For all identified contributions from science and practice, we additionally carried out a forward and backward search, which led to three further papers. Although we specifically searched in the listed journals and magazines, in a next step we conducted an additional open Google search (forward and backward search) to broaden the search frame. Table 1 shows the search results using all keyword combinations in the respective sources. The information in brackets behind the respective sources indicates the source of literature (P for practice and S for science).
A source is considered as relevant when it deals with digitization or transformation technologies in the maritime logistics. The review was executed by sorting the contributions by title, keywords and the abstract. After reading title and content specification, we decided whether or not we further analyze a contribution by reviewing the content or the abstract. A total of 124 contributions were identified as relevant and analyzed closer. Table 2 shows the list of publications title, grouped by major topic and subtopic(s).

Results
The results of the literature analysis are depicted in the concept matrix in Table 3.
In the following, we assigned the publications to subject-specific clusters and analyzed them accordingly. Before explaining the defined clusters in more detail, it must be pointed out that the individual contributions do not always allow for a clear assignment, since they often refer to aspects of different clusters. Therefore, the respective thematic main focus of each contribution was decisive for its clustering.
In the practical as well as the scientific literature of the years 2003 through 2017, a total of 124 relevant contributions covering the topic of digitization in maritime logistics were identified. The publications cover a broad spectrum and show the areas in need of development. It is striking that in the analyzed literature there is no systematic literature review on digitization in maritime logistics and it must be assumed that no literature review has been carried out on this topic until now. The majority of the identified contributions (88%) stems from IS-, maritime-and management-related journals or conferences, the remaining contributions (12%) are book publications. Furthermore, 22% of the articles originate from the general transport and logistics sector, 33% are IS or managementrelated articles and almost half of the identified contributions (45%) stem from the maritime logistics sector. Almost all publications are written in English (98%), which is related to the fact that the keyword search in the search engines of the literature databases and trade journals was carried out in English. In addition to the search in the literature, we carried out an open Google search (forward and backward) by applying all keyword combinations. In comparison to the scientific contributions, all 72 practical contributions were published in maritime-and transport-related journals. Of these, 39 contributions (54%) were written in German, the remaining 33 contributions (46%) in English.
Furthermore, we looked at the countries of origin of the respective leading authors in the scientific literature, or rather their institutions. As to the scientific literature, there is a strong concentration of  (7), (10), (68), (74) Cloud-based eBusiness (2), (6), Reporting (33) authors from the EU (55%), followed by authors from Asia (31%), North America, and Australia (6%) as well as Egypt (2%). Considering the identified practical contributions, the share of authors from the EU is similarly high (62%). The remaining articles originate from North America (38%).
Given the fact that artifacts such as big data, simulation and modeling and sustainable maritime transport play an important part in the digitization of maritime logistics, and thus are equally essential for all involved stakeholders, it is comprehensible that many of the identified contributions address such artifacts as well as the corresponding ICT. It is, however, surprising that only few publications stem from the maritime industry (i.e. shipbuilding and offshore industry). From the above results, it is clear that within the scientific community the research field digitization of maritime logistics is still in its initial stage. In practice literature, the situation is different as can be seen from the following contributions: The optimization of processes in the maritime logistics chain by new technologies and the resulting reduction of costs (Lüders, 2016), the transparency of the sea transport by sensor chip technologies (De Jong, 2017a) and the autonomous navigation and the subsequent reduction in ship occupancies (Selzer, 2016) are often discussed topics. Nevertheless, the analyzed publications show a clear homogeneity regarding the benefits of digitization for maritime logistics. Research studies (13) Emissions (12) Legislation infrastructure (26) Sustainable maritime transport (5) Implementing (20) Energy efficiency (29) Green supply chain (50)

P E S T E L
Challenge 1: Compliance with future stricter environmental requirements:

Environmental
The maritime logistics chain will change as a result of increasingly stringent environmental directives. The environmental directives limit the sulfur content of bunker oil at 3.5% from January 2020 to 0.5% (Gilbert, 2014). Since 2015, 0.1% has already been applied to areas which are particularly protected. A climate friendly and forward-looking fuel is, among other things, liquid natural gas (LNG), in its use in the long term hardly anyone will pass by (Brandt, 2016). However, when a shipping company converts to low-emission engines is an individual decision. CO2 emissions and noise can be avoided in the ports by feeding eco-friendly electricity from ashore side into the onboard network.
Challenge 2: Digital transformation of the maritime logistics chain + Data security and data protection Technological Digitization will change maritime logistics through intelligent networking of logistical processes and automation, and will contribute to increasing efficiency in shipping, management and service (Brouer et al., 2016), in which business models and their processes will be changing significantly in the foreseeable future: • Real-time tracking of cargo and cloud-based monitoring of ship systems are no longer a future issue (Biccario et al., 2014).
• The remote controlled or fully automatic ship operation will become reality in the foreseeable future (Maluck, 2016).
• Digital players will enter the market as competitors and support the digital conversion of maritime logistics with technical solutions (Brandt, 2016).
The stakeholders of maritime logistics should adapt themselves to new competitors, invest in digital business models and in the future assume more tasks in the maritime supply chain in order to remain viable. Digitization will force shipping companies to deepen their service portfolios and cover the entire supply chain, not just at sea but also increasingly on land (Brandt, 2016).
The growing volume of data, the demand for mobility in logistics and the exchange of information also lead to a growing need for data security and data protection in maritime logistics in order to prevent manipulations of sensitive systems. Existing defensive concepts (defense-in-depth models) are increasingly reaching their limits. Companies should protect their data against unauthorized access and any kind of abuse by cloud-based user systems, access management, device management and data backup, and make appropriate investments in IT security. Challenge 3: Big Data in maritime logistics + Process optimization

Economic
The use of Big Data holds potentials and risks at the same time: • Operational planning and control processes can be improved in the maritime supply chain (Brouer et al., 2016).
• Based on mathematical algorithms, based on real-time data from ship operation, ship arrival times can be predicted earlier and more accurately.In the future the stakeholders, involved in the maritime logistics chain, will be able to adjust their resource dispositions flexibly in an early stage to adapt to the ships arrival time.
The significant volume growth in the area of container traffic, as well as other maritime transport services, poses major challenges for the logistics chain. The actors of the maritime logistics chain should present and model the existing processes in a process optimization software and then optimize them. In addition to the development of meta-simulation models, for example for container terminals in the seaports, with a discreet, event-oriented character, optimization methods from other economic sectors could also be taken into account and these would then be made use of for maritime logistics. Examples of Lean Management, from the further development of the term Lean Production, should be mentioned here. This creates opportunities for improving the quality of the maritime supply chain as well as increasing productivity and optimizing the process as a whole.
Ship arrival times can be optimized and more accurately predicted, using new technologies as well as reduced waiting times in ports (Fruth, 2016). Equipped with RFID technologies, the path of a product can be tracked and monitored in a container, from the consignor to the consignee, without any gaps (Bai et al., 2010). The goods are cross linked across borders. Operating conditions and coordinates of goods can be interchanged and communicated. Financial support:

Political
For years sea shipping has been in one of its most severe crises. There is no fresh capital to modernize fleets or to implement other large scale projects, because for many banks an engagement in shipping is no longer an option. In difficult times like these, many maritime companies hesitate to invest in new technologies due to high investment costs. One of the most important challenges is to motivate and promote maritime companies for the introduction of new technologies, for example through financial support measures by the Federal Ministry of Transport and Digital Infrastructure (BMVI) and through government sponsored funding programs for the maritime economy and research.

Legal
The use of the AIS (Automatic Identification System) and RFID technologies requires the automated recording of personal data in some applications. When using the AIS technology, ships have a transponder on board, identify themselves among themselves, as well as with traffic control centers on land, and make relevant static, travel related and dynamic data clearly known. Personal data of the watchkeeping officer or captain are also transmitted. In these cases there are ethical and legal concerns regarding the privacy of the respective crew members. These data are available for everyone who has a corresponding receiver and can therefore pose a threat to the ship and its crew members when the ship is, for example in driving areas, affected by pirates or other criminal acts. Prior to the implementation of these technologies, restrictions on privacy and data protection should be reviewed by legislation.
In addition reliable and political framework conditions, especially in the course of digitization and automation in the maritime logistics chain, are recommended so that seaports can continue to function as logistical hubs. Regulatory guidelines, on the part of the governments, could make the economic development of port cities and entire coastal regions more difficult. Uniform conditions of competition, as well as an environmental policy that would allow for future development opportunities for seaports, would be a possible approach. Challenge 6: Social impact of digitization on the qualification and competencies of specialists in maritime logistics:

Social
Through the digitization and automation of many areas maritime logistics will change.
Smart-Shipping will create more attractive and responsible jobs onshore for the monitoring and remote maintenance of ships (Binder, 2016c). However, the use of new technologies requires appropriate expertise and the need for advanced skills. An increasing need for training and development in the field of new technologies will be necessary in the future. The major challenge is therefore to create and develop new competencies, to optimize project organizations and to gain new talents. Experience, willingness to integrate and technical knowledge are among the most important issues that should be considered.
Companies should work with their employees to develop ideas, for example on the basis of "planning games", how they can implement these things and introduce ideas for the creation of innovations. This enables effective analysis of business processes as well as the disclosure of existing improvement potentials by realizing company processes. Furthermore, interdisciplinary groups could be formed to work together to increase the efficiency of the companies.
In the area of new technologies and Big Data Analytics, the authors analyzed an efficiency increase in the area of ship operations, as well as an optimization of the maritime traffic through the exchange of data between ship-ship and ship-land actors and the use of ICT (Haraldson, 2015;Roumboutsos, Nikitakos, & Gritzalis, 2005). Port Community Systems (Carlan, Sys, & Vanelslander, 2016) and e-transformation systems based on IT transform and enhance the internal and external value chains as well as the transshipment activities in the ports . The smart, RFIDequipped container contributes to the sustainability of sea transport and significantly improves the transparency and security of international intermodal container traffic (Haraldson, 2015). In addition, RFID technologies enable the involved stakeholders to ensure a complete transparency along the entire process chain (Prokop, 2012).
Based on the AIS technology, real-time monitoring can be used to prevent pollution and protect the environment, as AIS technology optimizes maritime traffic, reduces the risk of accidents and minimizes environmental pollution (Yao Yu & ChangChuan, 2011). The fact that sustainability in the field of sea transport is a central and forward-looking theme, the actors of the entire maritime logistics chain are faced with corresponding challenges (Psaraftis, 2016;Stevens, Sys, Vanelslander, & van Hassel, 2015). The topic of cyberattacks and data misuse is also given much consideration in practical literature (Segercrantz, 2016a), as there is consensus that digitization is supposed to improve cybersecurity (Binder, 2016a) and needs a legal framework (Fabarius, 2017c).
As in other areas of the economic world, the analyzed literature shows that digitalization does not only bear chances but also risks, such as data misuse, cyberattacks as well as the loss of certain jobs for the maritime industry ( Bendel, 2015;Sen, 2016), which must also be considered.

Discussion
The results indicate that research in the digitization of maritime logistics is still in its initial stages. Our wide-ranging search revealed only a small number of scientific literature and shows that digitization in the maritime logistics chain is currently being addressed and considered rather in practical than scientific literature. With regard to our research questions, we come to the following conclusion: Digitization has already reached in maritime logistics in some areas and its potential to change the maritime industry is huge. Automation and digitalization are progressing and have changed processes in ship operation and in port handling. Smart container technologies (RFID) and real-time tracking of cargo, for example, increase the transparency on the transport route from the sender to the recipient. Shipping companies are already in a position to operate their own tracking apps in the near future, where the location of the container can be determined by means of a GPS signal (Brandt, 2017). By using modern sensor chip technologies, a large number of data are already recorded at sea and analyzed onshore, which allows the optimization of process flows on board as well as in the handling in ports. Further, it reduces waiting times and costs (De Jong, 2016). The focus of the identified papers is on the optimization of ship operation and terminal transshipment procedures by means of GPS, ICT as well as closely networked stakeholders. However, the areas of sustainability, emissions reduction, use of alternative fuels, as well as the risks of cyberattacks find little consideration in the identified literature. A growing volume of data in the area of the optimization of maritime traffic, port handling operations, and smart container technologies (e.g. RFID and sensor technologies) is expected.
Digital technologies will ensure shorter waiting times for ships and faster processing at the terminal. Besides, ship crews will be able to adapt their navigation using real-time updates to weather, wind, and ocean currents, which involves reduced energy consumptions . In view of the MARPOL 4 guidelines on climate protection and stricter environmental requirements, the shipping companies will have to equip their fleets with more environmentally friendly marine propulsion systems in order to be able to use alternative fuels such as liquefied petroleum gas (LNG) in the future (Brandt, 2016). Although the emissions in ports are already being slightly reduced by the use of marine diesel instead of heavy oil, CO 2 , nitrogen oxides, particulate matter and sulfur oxides are the main sources of the environmental pollution. To reduce such pollution, electric energy could be fed into the ship's network from onshore, which would require appropriate connections and converters (Winkel, Weddige, Johnsen, Hoen, & Papaefthimiou, 2016). Thanks to the digitization, it is further already technically possible to monitor the system ship from a central station onshore. In the future, the technical know-how will be needed rather onshore than on board of the ships (Binder, 2016c).
The digitalization in the maritime logistics sector offers a multitude of opportunities and challenges. For example, companies could take advantage of the digital transformation and position themselves on the market with applicable products, services or innovative business models (Brandt, 2017). On the whole, one can safely assume that there will be fundamental changes in ship operation and ICT. The shipping companies are assuming that, as a result of digitization, companies such as Google and Amazon will support the digital conversion of the shipping industry through technical services and will have to confront an increasing number of new competitors. Given this dramatically changing performance spectrum, also the shipping companies are forced to increasingly assume new tasks in order to remain competitive (Brandt, 2016).
As in aviation, the unmanned operation of ships is also feasible in maritime shipping. Experts predict the use of autonomous feeder ships that will transport containers on particular routes with limited reach. However, their opinions diverge as to when the first unmanned seagoing vessel will travel over the world's sea. On the industry side, it is assumed that the first autonomous ship will become a reality at the end of this decade (Maluck, 2016). According to the IT industry, however, it will still take 15 to 20 years (Kuchta, 2016). Given the high complexity of variables, many of them being unknown or difficult to predict (e.g. tide, weather, terrorism, emergency situations, increasing ship traffic), it is rather unlikely that large seagoing vessels can entirely be operated without staff (Berg & Hauer, 2015). And yet, the electronic on-board systems are in a position to take over a large part of the tasks and provide support so that the crew sizes will be further reduced (Burmeister, Bruhn, Rødseth, & Porathe, 2014).
As any networked data system, ships are also an attractive target for hacker attacks. The realtime data transmission of the smart, RFID-equipped container renders transparent the container's position, its content, and the state of goods at all times. Likewise, it can be traced whether the container was opened illegally or not. This transparency can indeed conceal immense dangers, such as criminal cyberattacks or unintentional data leaks (Berg & Hauer, 2015). The digital navigation systems of the ships could be manipulated so that they sheer off or run aground. Also a single power failure can have far-reaching consequences in a networked and digital environment (Kuchta, 2016). In maritime logistics, a large number of mostly international stakeholders are involved in transport processes. The increase in digitization and networking between ships, shipping companies, port companies, offshore installations, authorities and other communication partners onshore increase the risk of cyberattacks for all stakeholders involved. Therefore, all players in the maritime supply chain will have to ensure the best possible protection in order to ward off cyberattacks, which has to be ensured by consequently investing in the future development as well as expansion of IT security systems (Segercrantz, 2016a).
Due to the resulting logistics processes, the information requirements and the requirements for the logistical planning and control processes are high. As a result, protected and effective ICT gain in importance in maritime logistics as they contribute to increasing safety and effectiveness in maritime transport and port management (Jahn, Bosse ,& Schwientek, 2011). The results of the literature analysis indicate that the digitization of maritime logistics is still at the beginning of its development. So far, only sub areas have been investigated which hardly provide a basis for developing wellfounded recommendations for the maritime logistics. For this reason, the authors propose recommendations for action that are structured in the PESTEL matrix (Kaplan & Norton, 2008) summarized in Table 4 in six dimensions (political, economic, social, technological, ecological and legal).

Limitations
Like all other scientific papers, this article also has limitations. There is thus the possibility that not all relevant articles in the selection phase were filtered by means of keywords. There are various reasons for this, e.g. the incompleteness of the defined key words, the alternative concept names in the articles and the limitation to predefined publication outlets. The categorization of the articles also requires a substantive examination and evaluation, in which a distortion by the authors' subjectivity is never completely excluded. This article, however, provides important new insights and discusses the current state of research on digitization in maritime logistics.

Closing considerations and implications for science and practice
By means of a systematic literature analysis, it is possible to cope with the confusing amount of practical and scientific literature in the research process. Research gaps can be identified on the basis of the current state of science, and the corresponding research needs can be formulated. In this article, the status quo of digitization in maritime logistics was discussed by means of a systematic literature analysis of published articles from scientifically representative trade magazines, books, web pages and conferences, with regard to content and methodology dealing with digitization in maritime logistics. To the best of our knowledge there is, up to now, no systematic literature analysis on digitization in maritime logistics, neither in maritime specialist publication outlets, nor in a VHBranked journal, although the research topic proved to be relevant. In the area of sustainable maritime transport aiming at the reduction of ship emissions by means of alternative ship propulsion, there is a corresponding need for development, since it is the topic of the future in sea transport with only a few publications in the scientific literature. The majority of the publications are research results in specialist journals and specific conference volumes. A large part of the publications was also found in the so called grey literature. The study and its results show that practice recognized the development potential. Nevertheless, research is still at an early stage. On the one hand, there is a lack of theoretical studies that examine in more detail the future behavior of actors in the maritime logistics chain. On the other hand, alternative explanatory approaches to recommend appropriate action and restructuring are missing. We therefore recommend to expand this research into areas where information and big data projects have already been implemented. The aim of the research in this area is to provide robust contributions to theory that are characterized by high and clear predictive power of expression and as well as theoretical interpretations. These artifacts could be achieved by methodological and theoretical triangulation.