*2.1. Project Management Maturity Models*

The maturity in managing projects implies the established, proven, and innovative practices and procedures that lead to success in planning and completing projects [25]. Companies in various industries are pursuing improvements in project management maturity. A PMMM can enable an organization to seek perfect project management by implementing gradual maturity improvement processes within the organization [26]. PMMMs are regarded as the useful tools for evaluating an organization's current project management capability [27]. Project management capability is the competence required to ensure an organization remains competitive when conducting projects [28]. Capability frameworks are the basis for maturity models that address how capabilities can be developed along an anticipated, desired, or logical path [29].

The successful application of the CMM in the software industry inspired the development of the maturity model for project management. A PMMM is a complete framework and a comprehensive tool for evaluating the maturity level of project management. Since its creation in the 1990s, it has been used to systematically improve the maturity level of project management. As higher project management maturity levels represent the ability of organizations to obtain better results from their projects, the stakeholders of organizations are willing to assess their current project management maturity status for future development and improve to the next phase if desired [30].

After more than 30 years of development, many PMMMs have become available. The Microframe project management maturity model is one of the earliest PMMMs to be applied practically [31]. The Berkeley project management process maturity model, known as PM2 and presented by Ibbs and Kwak, determines and positions an organization's relative project management level based on those of other organizations [32]. A five-scale PMMM known as K-PMMM [33], which was established by Kerzner, analyzes the efficiency of project management organization, drawing attention to the importance of strategic project management to improve know-how in the marketplace. PMS-PMMM, which was released by Project Management Solutions in 2001, combines the five maturity levels proposed by the Software Engineering Institute and the project management knowledge areas proposed by the Project Management Institute (PMI) to form a comprehensive, easyto-accept project management maturity improvement model [34]. The organizational project management maturity model (OPM3) introduced by the PMI not only provides a systematic assessment and improvement method for the enterprise from a single project to entrepreneur portfolio projects, but also introduces and solidifies the best practice in every business process [27]. The portfolio, programme, and project management maturity model (P3M3), which was developed by the UK's Office of Government Commerce, comprises three independent sub-models (portfolio, programme, and project) and considers all seven processes as equally important. In the P3M3, the lowest maturity of the seven processes is the maturity of the organization [6]. In 2016, the International Project Management Association (IPMA) developed a methodology called "IPMA Delta" in order to certify the ability of an organization to use project management techniques. The assessment results of IPMA Delta show, in detail, the room for improvement, also giving recommendations for the future areas that need to be refined. MMM, focusing on a strategy of continuous improvement and following the four steps of the PDCA cycle to put this approach into practice, was developed by Langston and Ghanbaripour [35].

The only feature on which almost all models seem to converge is the determination of five maturity levels, even if they are not perfectly equal, either in the contents or in the denominations [36]. These levels and the corresponding main models can be summarized as follows:


In recent years, PMMM research has been expanded, and many scholars have investigated project risk management models [37,38]. Silvius and Schipper developed a sustainable PMMM as a practical tool for the assessment and development of the integration of sustainability in projects [39]. Seelhofer and Graf extended the concept of organizational project management maturity to the national context and developed a systematic framework of national project management maturity and the national PMMM [40].

Since most PMMMs are based on a guide to the project management body of knowledge (PMBOK) of PMI [41], by adopting PMMMs, organizations can systematically plan and improve their project management capabilities and benchmark their performance in accordance with the industry standards [31]. The assessment of maturity through PMMMs enables further improvement directions to be identified [26].

Despite their similarities, PMMMs differ from each other in terms of their assessment methodology. Hence, selecting an appropriate PMMM is a crucial managerial decision, and the organizational environment and project characteristics must be considered well to ensure the suitability of the selected model [30].

#### *2.2. BIM Maturity Model*

Over the past decade, a large number of BIM maturity models have been developed to measure the performance of BIM application. BIM maturity models are mainly divided into two categories [17,42]: one is the project BIM maturity model focusing on project application performance, and the other is the organizational BIM maturity model focusing on enterprise implementation capability. The famous project BIM maturity models include NBIMS CMM, iBIM, and VDC Scorecard, and the famous organizational BIM maturity models include BIM PM, BIM MM, BIM Quick Scan, and BIM AP. In addition, there are individual models that can be applied to the BIM maturity assessment of both organizations and projects.

The U.S. National BIM Standard (NBIMS) was published in 2007 and provided information as a guide for the adoption, implementation, and application of BIM to enable core principles. The Capability Maturity Model (CMM) of NBIMS is a matrix with 11 interest areas on the *x*-axis and 10 maturity levels on the *y*-axis [43], and is a useful tool for the strategic management in the BIM implementation of an organization [44]. The interactive capability maturity model (ICMM) is a further enhancement of CMM, developed to meet the growing need for an accurate and up-to-date model [45]. Bew and Richards developed the iBIM maturity model in 2008. Its assessment indexes focus on technology, standards, guidelines, classification, delivery, etc. Its maturity is divided into four levels. Level 0 is characterized by paper-based medium delivery methods. Level 1 represents structural elements by 2D or 3D digital objects. Model-based collaboration occurs in Level 2 between different parties, and network-based integration occurs in Level 3 [46]. VDC Scorecard was designed to measure the performance of the projects of virtual design firms with four major areas, 10 divisions, and 74 measures. Its distinct feature is the establishment of confidence levels to measure the degree of objective compliance [47]. VDC Scorecard has both quantitative and qualitative assessment methods with multiple choice and open-ended questions. It assesses performances of BIM projects against the industry benchmark and has five maturity levels.

The BIM Proficiency Matrix (BIM PM) was developed by Indiana University Architect's Office to score the performance of BIM services of designers and contractors in Indiana University projects [48]. BIM PM is composed of 32 measures of eight areas and five maturity levels [17]. It has also been criticized for its heavy focus on the technical aspects of BIM implementation rather than process and protocol. The BIM maturity matrix (BIM MM) is multi-dimensional and can be represented by a tri-axial knowledge model comprising BIM Fields, BIM Stages, and BIM Lenses [49]. The model proposes five BIM maturity levels: initial, defined, managed, integrated, and optimized [50]. BIM MM assessment can be provided by the online BIM Excellence platform. The question number of assessment varies according to the assessment granularity level, and a maturity score is compiled related to 12 positions grouped into five areas [51]. BIM Quick Scan developed by TNO (The Netherlands Organization for applied scientific research) is a benchmarking tool for organizational performance with a reasonably extensive scope covering 44 measures in four main areas, including: organization and management, mentality and culture, information structure and information flow, and tools and applications [43]. It can combine quantitative and qualitative assessments of the "hard" and "soft" aspects of BIM, and distinguish the strengths and weaknesses of BIM application for an organization. Organizational BIM Assessment Profile (BIM AP) was created by Pennsylvania State University Computer Integrated Construction (CIC) Research Program in 2012. Its maturity is measured by 20 planning elements with six themes: Strategy, BIM Uses, Process, Information, Infrastructure and Personnel, Companies. Their maturity levels range from 0 (Non-Existent) to 5 (Optimizing) [22,51].

The multifunctional BIM maturity model (MPMM) focuses on BIM maturity at different scales from individual projects to an organization's full projects portfolio, covering measurements across three domains: technology, process, and protocol. Detailed, operable

rubrics enable the assessment of each subdomain of each domain, and the assessment result points to four maturity levels (0–3) [52].

From the above introduction, it can be seen that these existing studies mainly focus on the technology capability maturity of BIM from different perspectives and conditions, and ignore the digital twin relationship between BIM and projects. In addition, a large number of BIM maturity models have different assessment indexes and different level definitions. As a result, users can be confused and do not know how to choose assessment models.
