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Decision Support Systems in Construction: A Bibliometric Analysis

: In recent years, the use of decision support systems for selecting sustainable construction materials in the building and commercial construction projects has received a great deal of attention. This paper reports an in-depth and systematic bibliometric analysis of the literature using Decision Support Systems (DSSs) for its construction, based on the papers published during the period from 2000 to 2016. The data were collected from two major databases, Web of Science (WoS) and Scopus, which included 2185 and 3233 peer reviewed articles, respectively. The analysis includes a general bibliometric analysis (publications output, country-wise research output, authorship, and collaboration patterns of these published articles). It also includes a citation analysis (keywords, most cited keywords, organizations, most cited articles, and average citations per article) and a network analysis (authors and countries). Overall, this study provides bibliometric insights and future research directions for researchers and practitioners who use DSSs.


Introduction
The construction sector has evolved over time by adopting the latest technologies for different phases of construction, including design, execution, and operation. Each phase has its own importance-e.g., selecting the right design parameters is considered the backbone of a construction activity. Selecting the correct construction materials to satisfy design and operational specifications also has unique value. Technological shifts have made the construction process more demanding, thereby also making the jobs of the technical personnel more challenging.
Information technology is playing a critical role in making this job even more precise, accurate, and fast. By offering innovative information systems, such as neural networks [1], decision support systems [2], and expert systems [3], the work of technical stakeholders and managers has become very simple and fairly accurate.
From the very beginning, design software such as AutoCAD [4], Building information modelling (BIM) [5,6], Structural analysis program SAP 2000 [7], Extended 3D (three dimensional) analysis of building system (Etabs) [8], Revit building information modelling software [9] has injected a new spirit into the modern construction process. Similarly, PrimaveraTM [10] and BuildsoftTM [11] are good for use in construction execution, control, and monitoring systems. The rapid growth in the construction sector has made the construction manager/decision maker's job more hectic and tedious. Information technology in the form of decision support systems is now helping to make this job easier, more reliable, and more accurate.
In recent decades, many scientific articles were published in the field of decision support systems in construction, studying, for example, optimal cost analysis [12,13], multi-objective optimization [14,15], Multi-criteria decision analysis (MCDA) has been considered an appropriate method to carry out performance evaluation due to its flexibility [58]. The assessment process infers the presence of tools, processes, specifications, procedures, and methodologies for steady performance under the umbrella of sustainability [59].
Moreover, green roofing has been a topic of interest for the last two decades. The number of relevant publications has increased dramatically in this time period. USA and Europe were the main participants in this research direction [60]. Vernacular construction is more concerning in Europe due to its limited infrastructure development and altered land conditions. Different materials and construction methods have been adopted to better understand the recovery of Spanish bioclimatic architecture [61].
Overall, there are a number of research directions within the broad umbrella of decision support systems for construction. These directions include energy conservation, energy management, operations and management, energy retrofitting, uncertainty and sensitivity analysis, maintenance, estimating project costs, future project costs, and green roofing.
To understand the progress in this field, a systematic analysis of the literature using a bibliometric methodology is required. When we studied the literature, we found some previous related works in this field. For example, Ying Chen found that prefabrication can offer a substantial opportunity to maintain sustainability but that the decision to apply a method is largely based upon personal preference rather than available datasets [62]. Shaddy Attia said that there is a need to develop a decision support system to integrate energy simulations into the early design of zero energy buildings [63]. Xiaodong developed a decision support system for strategic maintenance planning in wind farms. This decision support system is based upon two optimization models. One is the deterministic model used to find accurate failure rate data, and the second is the stochastic model, which is used to determine the failure rates with less certainty [64]. Igor studied the latest progress in heuristic based decision support systems to select alternate routes in a large-scale transportation transit system. He found that, normally, computer-based Decision Support Systems (DSSs) are good to use in computer analysis programs but difficult to implement in real-world problems. He developed a formal method using the Petri Net model [65].
A substantial amount of research has been undertaken in the last two decades on bibliometric studies in construction. For example, a bibliometric analysis was done by Ignacio regarding the evolution of construction and building technology. Ignacio's paper describes the evolution of the merits of various researchers and research institutes [66]. The current trends in solid waste management are discussed by Lie Yang. This topic has become very interesting due to limited resources, the exceptional increase in the world's population, rapid urbanization, and global industrialization [67]. Lior Blank investigated the directions in green roof research, which is a multi-disciplinary field of research. Green roofs provide more benefits than their alternatives (such as heat flux, vaporization, and insulation), except for aesthetics [60]. Energy efficient building renovations are discussed by Jonas. More than 30% of global gases are produced by the building sector. Thus, this sector requires the most efficient renovations to reduce this factor [68].

Methodology
Bibliometric analysis describes and analyses up to date research and provides guidance on future directions for researchers and practitioners. It aims at summarizing the latest progress in the field by investigating the literature in a quantitative manner. Some researchers find bibliometric analysis a useful tool to obtain comprehensive insight into specific research areas, while others seriously question the validity of this approach.
Giovanni Abramo noted that bibliometric analysis is much more reliable than peer review [69]. Rodrigo Costas stated that bibliometric indicators are very useful for developing research policy and monitoring technological activities [70]. Briger argued that this method is useful for recognizing candidate terms and organizing knowledge by relating scientific papers to their authors, thus indicating their relatedness and semantic differences [71]. Diana referred to this method as an unparalleled opportunity to take advantage of the rich information embedded in the written products of scientific research to determine the output and influence of funded scholars [72].
Conversely, some researchers have identified major disadvantages to this technique. Lutz Bornmann mentioned that percentiles and percentile ranking have limited use when there are the same number of citations for an article. The size of the reference set is always an important factor while setting up the classes for ranking [73]. The H-Index is another factor that has some issues in providing accurate facts and efficacy [74].
Overall, this method provides a vast canvas of knowledge from the micro level (institutes, researchers, and campuses) to the macro level (countries and continents) [75]. This technique can provide more information about the relationship between different research directions among various universities. Citation and content analysis represents the most widely used criteria that can (1) tell us about the citations and citation trends in a specific field of knowledge and (2) describe the direction of modern research by presenting the most widely used author keywords.
In this paper, we computed the following major trends: relative growth rate (RGR), doubling time (DT), collaboration index (CI), collaborative coefficient (CC), and international collaboration papers (ICP), with most productive institutes and authors under the headings of the (TP) and (TC) plots. The text analysis approach is also applied to determine the major research hot spots [76]. Frequency analysis is used to find the most commonly cited and most commonly occurring keywords. A topic density plot for the control terms is also developed to provide information on the major research trends in the field. Science mapping is carried out using the VOS viewer tool [77,78].

Data Sources and Collection
This bibliometric analysis was conducted using selected journal articles specialized in the area of decision support systems in construction. These articles were accessed using the Scopus and Web of Science (WoS) databases. Access to these databases was provided by Curtin University, Australia. We performed a bibliometric citation and content analysis to obtain our research objectives.
A systematic approach was adopted when searching for articles using the following keyword: "Decision support system in construction". This search was restricted to the engineering, computer science, environmental science, decision science, soil science, applied energy, applied physics, and material science areas, since these fields are the most strongly related to construction and the multi-criteria decision making (MCDM) techniques used for decision support systems. Several other fields also appeared in the search results, such as medical science, management, agriculture, optics, ergonomics, internal relations, and many more, but they were excluded.
We further restricted our data collection only to articles, reviews, proceedings, and book chapters. Using this research strategy, we selected 3233 and 2185 articles from Scopus and WoS, respectively. Only articles published between 2000 and 2016 were selected in this study.

Data Analysis Tool
We used the VOS viewer as a tool to develop certain types of graphs (e.g., international collaborations and keyword density distribution). Further, we used NAILS (network analysis interface for literature studies) to sort the literature data into subjects, keywords, authors, citations, occurrences, affiliations, institutes, and locations [79].
Results and discussion: In this section, the different parameters are computed to determine the various aspects of the literature, such as year-wise contribution during this timeframe, growth rate, doubling time, authorship and collaboration patterns, major publication areas, and the subject-wise distribution of research work.

Publication Output (2000 to 2016)
The publication output is presented in Figure 1, which presents the annual number of publications in both Scopus and WoS under the heading "decision support system in construction". In  Figure 1 shows that there was a segmental but continuous increase in the research being undertaken in the field of decision support systems in construction. Although there were some instances of a downward trend in the stipulated timeframe, the overall trend experienced an upward trajectory.

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The growth rate per annum was calculated to find the incremental trend of yearly output and 255 the doubling time of the published articles, such as the time required to double the total number of 256 articles. In both the databases, both of these parameters were calculated using the following formula 257 [80]. This formula was used by Mahapatra [81] to find this parameter and its significance.

Relative Growth Rate (RGR)
The growth rate per annum was calculated to find the incremental trend of yearly output and the doubling time of the published articles, such as the time required to double the total number of articles. In both the databases, both of these parameters were calculated using the following formula [80]. This formula was used by Mahapatra [81] to find this parameter and its significance.
where CN 2 and CN 1 are the cumulative number of publications each year.

Doubling Time (DT)
The doubling time (DT) has a direct relationship with the relative growth rate (RGR). It gauges the time required to double the existing number of publications and is calculated using the formula reported in [80]: Table 1 shows the sequential increase in the research output by cumulative number, relative growth rate (RGR), and doubling time (DT). It is evident from Table 1 that there is a significant increase in the overall research output. The RGR and DT values show a clear upward trend for Scopus and WoS, which demonstrates the significance of this topic. The WoS showed a segmental increase and decrease, as well. Collectively, both indicate the dominance of Scopus in this area over WoS, except for 2015. Table 2 shows the top 15 contributing countries researching this field. Table 2 shows that out of 5418 articles, the People's Republic of China is ranked number one, with 1030 articles (588, 442), providing 19.01% of the contributions to this field. Indeed, China has a very large population, and its housing and infrastructure projects play an important role in shaping the country's overall economic canvas. China's socio-economic conditions over the last 17 years from 2000 to 2016 were quite different to some of the worlds developed economies. Hence, the research undertaken in developed nations cannot not be easily adopted to the Chinese construction sector. Further, China has a significantly higher population and building density and less reusable energy per square meter of floor area [82]. These unique factors create a unique need to research this area. Consequently, China has produced its own research to find the best solution to its specific problems, which is one of the reasons why we see such a significant contribution from Chinese researchers.

Major Contributor Countries
Next is the USA (602, 389), with a total of 991 articles, contributing 18.29% of the field's research. England is in the third position, contributing 388 articles (7.161%). Canada is in fourth position with 5.44%, Germany is in the fifth position with 3.82%, and Australia is sixth, with 3.61% of the contributions. The remainder of the contributors are shown in Table 2. Notably, European countries make a prominent appearance in the top 15 major contributors in the field of decision support systems in construction. Europe shares some common problems with China, such as limited usable land [83]. From an environmental perspective, the use of natural building materials in residential construction is far better than the use of bricks and other processed materials. For example, a wood-based house is 7.5% better than a brick house [84]. This is a concern for European countries because demolition is very common, which leads to construction waste, which causes serious environmental problems in its disposal. Thus, different strategies and laws were devised to tackle this issue. These issues have driven research in the area of sustainable construction [85], including legislation, policy development, etc. Figure 2 presents an international collaboration network using the international collaboration papers (ICPs). The graph shows seven clusters in different colors. It shows that China has the strongest ties with England and Australia, USA with Spain, Germany with Canada, and Canada with Taiwan.
Furthermore, China has the highest number of ICP instances involving several other countries, such as Iran, Singapore, North Ireland, and Scotland. Both of the largest contributors (i.e., researchers from China and the USA) also have close ties and collaborations in research, specifically in decision support systems. Stevan D. Glaser from the university of California USA and Hui Li Harbin from the University of Technology China and others have worked in collaboration to develop innovative sensor technology to assess and monitor the structural health of buildings [1]. Researchers from Australia and Hong Kong have worked to manage the web based information flow for large construction projects [86]. Researchers from Australia and USA have worked to develop information collection and delivery systems based on the contextualized model framework [87]. Other collaborations among countries are shown in Figure 2.
devised to tackle this issue. These issues have driven research in the area of sustainable construction 295 [85], including legislation, policy development, etc.

Authorship and Collaboration Patterns
To analyze the authorship and collaboration patterns, some important parameters were determined: Collaboration Index (CI), Degree of Collaboration (DC), and Collaborative Coefficient (CC). These were computed using the following formulas: Collaboration Index (CI): Degree of Collaboration (DC): Collaborative Co-efficient (CC): CI measures the mean number of authors per year and does not contain any upper limit. Thus, it cannot be interpreted as a degree [88]. It gives a non-zero weight for single-authored papers and for non-collaborative papers.
DC measures multi-authored papers, where "f 1 " is the number of papers written by a single author. Since DC has a value range between 0 and 1, it can be interpreted as a degree [89]. It gives a weight of 0 for single-author papers and 1 for multi-authored collaborative papers.
CC is used to quantify collaboration with a range of values between 0 and 1 (computed in Tables 3  and 4 [90]), where "fj "is the number of research papers in a specific field of study having "j" authors. "N" is the number of the research papers, and "k" is the maximum number of collaborating authors in that field of study [91]. Tables 3 and 4 show that most of the articles across both databases were written by multiple authors. Normally, articles featuring experimentation were written by two or more authors.
Most multi-authored papers are those that cover a large research topic or inter-disciplinary problems of research, such as light train transit systems [92], integrated water resource management [93,94], forests and timber harvesting [95], and different pollution patterns [96]. Some of those papers are written by authors from the same country [97] and some in collaboration with other countries [98]. The papers written by one or two authors handle much focused research problems, such as technical engineering issues [99], risk management, construction monitoring and decision support system (DSS) [100], e-procurement [101], infrastructure risk assessment [102], housing [103], and contractor selection [104].  Table 4. Authorship and Collaboration Patterns in Scopus.  Table 4 presents the top 10 contributing authors with their affiliated institutes. Notably, the top three authors are from Lithuania and Canada, which are of a lower rank in their overall articles published. "Zavadskas Ek" is first, with 42 articles, comprising 0.77% of the overall 5418 articles. Next are Abourizk, S. and Kaklauskas, A., who are both ranked second, with 32 articles, comprising 0.59% of all contributions. Cheng, M.Y. is ranked third, with 25 articles and 0.46% of the total contributions. Figure 3 indicates the international collaboration of authors who have at least two published articles with a minimum of two citations. Here, there are 14 clusters represented by different colored bubbles. The collaboration graph shows clearly that Skibniewski, M.J. had many collaborations with Hong T., Zhang C., and Lee S., while Shen QP collaborated with Li H.     Table 5 shows the top 10 organizations that contributed the most articles during the research period of 2000 to 2016 with relative percentages.  China and USA are both present in the top 10 positions in the Scopus and WoS databases. The rest of the institutes are from Taiwan and Singapore.

Top 10 Contributing Organizations
Chinese universities have prominent rankings across both databases, with Huazhong University of Science and Technology, China (30, 0.93%), ranked third and Tsinghua University, China (24, 0.74%), ranked seventh in the Scopus database. In the WoS database, Huazhong University of Science Technology, China (23, 1.05%), is ranked fifth, and the Chinese Academy of Sciences, China (21, 0.96%), is ranked eighth.
Purdue University, USA (29, 0.90%), is ranked fourth, and University of Maryland, USA (23, 0.71%), is ranked eighth in Scopus. Florida State University, USA (21, 0.96%), is ranked seventh, and University System of Maryland, USA (19, 0.87%), is ranked 10th.       Table 7 shows the top 25 most commonly occurring keywords from Scopus and WoS. We have 389 arranged these key words in descending order. We identified the high frequency significant terms 390 (i.e., control terms). It is quite clear from Table 6 that "Decision Support System", Decision Support density visualization of the most common key words. Figure 6 and Figure 7 show the Scopus and

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WoS keywords with at least five occurrences. It also shows the significant research keywords that 395 appeared in both databases.   Table 7 shows the top 25 most commonly occurring keywords from Scopus and WoS. We have arranged these key words in descending order. We identified the high frequency significant terms (i.e., control terms). It is quite clear from Table 6 that "Decision Support System", Decision Support Systems", and "Decision Support" are the most commonly occurring keywords, followed by "Data Mining", "Decision Making", and "Simulation". We used the VOS viewer to develop a keyword density visualization of the most common key words. Figures 6 and 7 show the Scopus and WoS keywords with at least five occurrences. It also shows the significant research keywords that appeared in both databases.

Inter Topic Distance Map (Latent Dirichlet Allocation, LDA)
We used the Latent Dirichlet Allocation (LDA) technique based on the idea that the probability of words can be expressed as a mixture of topics, where each topic is a probability distribution of the words. We utilized one of the popular models of LDA proposed by Blei et al. in 2003 [105]. In LDA, information collection is carried out in three major steps. For the given papers, distribution of the topic is sampled from Dirichlet distribution. For each word, a single topic is selected according to this distribution, and each word is sampled from a multinomial distribution of words specific to the sampled topic [106]. Figure 6 provides an inter-topic distance map via multidimensional scaling. It presents a graph with six circles showing different topic selections. We elaborated each topic and found the frequency distribution of each word that appears in each selected topic. Figure 7 presents the top words appearing in each topic selection and the top 30 most salient terms. The words clinical, cycle, decision, information, maintenance, model, projects, sustainability, and systems appeared in almost every topic distribution, with a strong number of appearances during each topic selection.

A New and Promising Area of Research
The bibliometric analysis conducted in this article provided us with a true archetypal illustration of the research and technology shifts in the field of construction informatics and helped us to understand the overall revolutionary impact that information systems (IS) and information technology (IT) have made in the field over the last two decades. The results also indicate ongoing growth in research output in this area since 2007. However, numerous independent studies were found to lack proper cohesion, which is mostly attributed to the fact that the researchers followed their own personal research trajectories in isolation from other researchers. This has led to isolated objects of knowledge in specific areas within this field of research. The majority of this research is dominated by China, followed by the USA. Some European countries are also actively engaged in this area of research, especially researchers from Lithuania, who are collectively far ahead at the individual level compared to China or the USA.
Within the decision support systems area, some key research directions focused on risk assessment related to construction costs [107], energy management [108,109], construction equipment selection [110], construction method comparisons between piled embankment and traditional sand construction methods [111], resource reuse development for sustainable construction [112], consultant selection [113], timber harvesting systems [95], construction value management systems [114], cost optimization for complex railway portal construction [115], very tall building development [116], international contractor ratings [117], and emergency service centre locations [118].
The following key research clusters were identified by the bibliometric literature analysis in this field: DSS for Construction Innovation: Research in this area investigated core issues such as the use of robots in construction, artificial intelligence, reconstruction materials, waste management, and cost control. The use of robots in construction that can work in real-time demonstrates the application of artificial intelligence in the construction sector [121]. The interaction of construction with the environment can be monitored using artificial intelligence by quantifying and spatially mapping the benefits provided by these systems [122]. Construction site selection [123] and demolition waste management (Marzouk and Azab, 2014) are field related factors. Several selection criteria, such as reconstruction materials [124], capital costs [125], corporate social responsibility [126], cost control [127], and construction visualization [128], were also identified by using the latest MCDM techniques, such as Electre III, which is used for optimal location selection for construction waste management [120]. The development of the innovation assessment index (IAI) and literature on IAI using rough set theory can be found in [129]. However, other methods (e.g., fuzzy approaches, data mining, etc. [130,131]) need further investigations. Similarly, low carbon technologies have been introduced on a massive scale to gauge global environmental change and sustainability and to boost the low carbon economy [132].
DSS for Design Issues: The research in this area focuses on the use of DSS to meet the design challenges in the construction sector, which is continuously being investigated [133]. The use of DSS for the purpose of designing mitigation strategies for construction safety risks was investigated by Qian and Lin, 2016. This system can increase employee safety at the start of the project (Titas, 2013). Most architects and engineers are concerned about risks and safety on site; hence, designing a risk analysis and mitigation approach is gaining attention in the literature [134]. Traditional building companies still follow old design processes, which limit the use of innovative energy efficient technologies. However, legislative changes are playing a critical role by introducing building codes that require energy efficient designs [135], simulation modelling with an e-commerce perspective [136], design flow [137], and decision support systems [137]. In the context of rain water tank design, design optimization can be achieved by using a simple decision support tool, such as a spread sheet containing rainfall data, the contributing roof area, the rainfall loss factor, the available storage factor, and tank overflow and irrigation water demand [138]. Algorithms designed with computational approaches have also been investigated to calculate the moments produced in steel frame structures to assess their impact on a building's structure [139]. Parametric modelling tools are used to combine complex structural designs with construction knowledge to develop generative rules and feedback rule checking criteria for conceptual design [140].
DSS for Construction Management: The research in this area focuses on the use of DSS for construction project management. Some key research directions include risk management modelling, domain knowledge management, flood management, and life cycle assessment to better understand the complexity of construction risk and safety management. Further, experience-based decision support and evolution model management system were developed [141]. Moreover, using domain ontology as a consistent platform for sharing project information, an artificial intelligent model was developed to relate the construction aspects of infrastructure products [142]. Conceptual multi model-based management information systems for simulation and decision making in construction projects were introduced to study both the management system owner and contractor firms and showed a paradigm shift (Kog and Yaman, 2014). Two dimensional GIS-based flood management decision support systems were shown to work practically within the framework of ArcGIS. This system can interact with remote sensing (RS) image layers and GIS feature layers [143]. Loosely integrated facilities and maintenance management systems were introduced; these systems work as a DSS by combining the transformation of the data, information, and knowledge captured and accumulated during the entire life cycle of a construction project [144].
Dynamic planning: This term is used for the combination of construction and project planning. The latest trends are discussed here for virtual construction site planning, irrigation planning, aggregate selection, 4D modelling, waste water infrastructure location planning, visualization tools, transport planning, and resource planning. Virtual construction site planning (VIRCON) [145], a decision support system (DSS), was developed to improve the planning and management of large irrigation schemes to analyze and evaluate the crops and crop scheme patterns cultivated to determine the limitations affecting crop selection based on yield [146]. The construction and maintenance of the infrastructure are based upon the selection of aggregate raw material. Lack of planning at the start can cause inconsistencies in the product cost [147], environmental performance [148], and confrontational relationship between the aggregate industry and community [149]. With the passage of time, the output from computer aided programs in the construction industry has become more demanding in order optimize resource utilization. The 4D model and 4D site management model were described to have a useful interphase with the 3D scheduled data from the computer graphics building model [150]. A combination of the planning and foundations of decision making techniques was discussed by Oleg, who noted a discrepancy between the evaluation of the attractiveness of techniques and methods from the perspectives of academics and managers of building companies [151]. Construction planning is driven by many factors, such as the definition of the work's tasks, estimation of the required resources, and the options of construction technology.
Geographic Information system (GIS)'s evolution has provided a new direction for the selection of waste water system locations in the terrains of specific areas. Different parameters were considered to minimize the construction and operational cost of such projects considering the topographic conditions of the area [152]. The construction industry uses planned areas because this industry requires many trades working simultaneously at the construction site. The GIS system is considered a good tool to assess construction safety planning [153]. To minimize the conflict between execution space interference in work-based activities, a critical space time (CSA) approach was developed by researchers using the computerized tool dubbed PECASO (Patterns execution and critical analysis of site space organization), which is a 4D space visualization and site planning tool [154]. Interchange is the most frequent and adaptable solution used to manage many intersections in the traffic planning process. The location issue is dealt with by merging different techniques and knowledge, such as bridge engineering, urban design, transport planning, technical specifications, and local and international standards, considering the structure, shape, landscape, and available site location (Rui, Qing-ning, Zhao-fei, and Zhao-hui, 2009). Construction companies are well-versed in using integrated planning and management software, such as ERP systems, to plan and manage mega projects in a precise way to avoid any jostles during the execution phase [155].
Fusion of the Latest Multi criteria decision making (MCDM) Techniques: Different multi criteria decision making techniques have been used under this heading, which clearly shows the pace of the evolution process and usage in the current construction industry. Major combinations include AHP and fuzzy and quantitative decision models. The limited resource factors of the government caused the emergence of BOT (Built, Operate and Transfer) projects. By incorporating the fusion of AHP and Utility Theory, an MDCM model was developed to support the selection process of BOT projects [156]. The execution of construction projects in a metropolitan area is risky, so competitive and dynamic approaches must be used to evaluate such projects. Fuzzy multiple criteria and fuzzy multiple attribute decision making approaches were established to systematically asses relevant risk factors [157]. The most important factor in the construction industry involves making accurate decisions at particular times and in particular situations. Multi-criteria decision making methods played a vital role in assisting this problem, particularly from an economic perspective [158]. Temporary housing units are used during the disaster management process. These houses are normally provided as prefabricated units that have many economic, environmental, and social issues. Thus, a DSS was developed to find the best functional value. The value function concept is used to facilitate this selection process when there is no other option [159]. Value analysis and multi attribute utility theory are used to determine the sustainability of the materials used in the sewerage pipe manufacturing process. The subjectivity involved is minimized by comparing the quantification of the different materials used in this process [160]. The reduction of carbon gases is treated as a major problem, especially during the construction phases. Almost 76% to 86% of this portion is produced during road construction. A quantitative decision model was developed to support the application of green technologies during road construction [161]. A decision model was developed by using quantitative measurement as an effective tool for big data analysis along with an algorithm to implement the latest modernization techniques in the building construction process [162]. A fuzzy expert system was used to develop a framework to identify and evaluate the causes of conflicts within a matrix organization in the construction industry. This system will help develop a suitable organizational structure that meets the requirements of the construction industry [163].

Conclusions
The basic aim of this paper was to provide concise information on the research topic of "Decision support systems in construction" to give future researchers and students to more detailed insight and more precise information using a bibliometric analysis, thereby synthesizing available information about the authors and countries with the largest numbers of contributions when searching for detailed work on this topic. This study endeavored to inspect the ongoing vagaries in the topic of decision support systems in construction. The factors discussed reflect the maturing stages and emerging trends in the field. There is no doubt that these stages are very common in the described years (2000 to 2016) of study. The gradual increase in the number of published articles shows an increase in the interest to work on decision support systems in the construction sector.
We found that China and the USA are the major players in this field of study, while Lithuania is the country with the top ranked authors. This trend shows the strength and growing trend towards DDS in the European region. Overall, the results are satisfactory for this research area, which continuously progressed over the studied period of time. In this paper, we successfully conducted analytic mapping of the research topic during the period of 2000 to 2016. The data obtained from Scopus and WoS, two major database sources, helped us analyze the different characteristics of our research topic. We used these two databases to obtain the raw data, and some combined research outputs and topics appeared during the data collection. We used these as single data-points to keep our data-set concise and non-repetitive. The basic motive to use bibliometric analysis was to study scholarly communication by tracing its history and evolution of ideas and quantifying the impacts of articles analytically. We provided details for the research output by year, country of output, countryand author-wise international collaboration patterns, authorship, important keywords, and a frequency visualization of those keywords.
All these analytical outcomes include computation of the latest bibliometric characteristics, including RGR, DT, CI, DC, and CC. We found and presented information about the top contributors in the form of countries and authors along with their affiliate institutes and their collaboration patterns both countrywide and internationally. The top authors and their fields of interest and research by year. The major future research directions include simulation modelling, artificial intelligence, construction automation, 3D prototyping, remote sensing and controlling, interactive value management, sustainable development, and management. We identified important control terms, comprehensive analyses, and the latest bibliometric characterizations in this research field.