Teachers’ professional digital competence: an overview of conceptualisations in the literature

Abstract Educational research has increasingly drawn attention to teachers’ professional digital competence.Various theoretical and methodological perspectives involving a plethora of terms are used to investigate teachers’ competences in relation to technology-based teaching. The concept of teachers’ professional digital competence still appears to be ambiguous and elusive. This literature overview aims to scrutinise if, and how the concepts addressing teachers’ professional digital competence are defined or conceptualised in research. In the publications retrieved from the search in educational databases, we found that the concept of teachers’ professional digital competence, or related concepts, was frequently mentioned in abstracts, keywords and full texts, but to a large extent, it was rarely described in detail. In our final corpus of 18 publications, we could distinguish seven recurring aspects of teachers’ professional digital competence; 1) technological competence, 2) content knowledge, 3) attitudes to technology use, 4) pedagogical competence, 5) cultural awareness, 6) critical approach and 7) professional engagement, with the technological and pedagogical competences as the most prominent. Inspired by Bronfenbrenner’s ecological systems theory, these aspects are analysed as operating within microsystems of individual teachers and within meso- and macrosystems of interactive teachers in interplay with the situated classroom contexts and on larger societal systems.


PUBLIC INTEREST STATEMENT
In the wake of the digitalisation of schooling, there is a growing interest among practitioners and researchers to understand what competences teachers need to teach with digital technology. With this paper, we contribute with increased knowledge of how teachers' professional digital competence is described in the research literature between 2010-2019. We found various terminology with definitions based in policy documents and/or previous research. Particularly, we identified seven aspects of competences with technological competence as the most prominent. These aspects are predominantly described as individual abilities, and as collective and interactive abilities that are dependent on the classroom environment. Moreover, a picture emerges that the responsibility for developing adequate digital competence rests with the individual teacher. Based on the findings, we argue for an understanding of teachers' professional digital competence that not only emphasizes technological competence. Furthermore, the responsibility for teachers' professional development should be placed at the school leader level.
Inspired by Bronfenbrenner's ecological systems theory, these aspects are analysed as operating within microsystems of individual teachers and within meso-and macrosystems of interactive teachers in interplay with the situated classroom contexts and on larger societal systems.

Introduction
In this overview, we will examine the concept of teachers´ professional digital competence (TPDC) as used in the research literature in the field of education over the last 10 years (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019). The concept of TPDC stems from the more general concept of digital competence, emphasised in various European policy documents (e.g., European Parliament and the Council, 2006;OECD, 2005) as necessary for active participation in a digitalised and democratic society. The notion of the digitally competent citizen has been implemented on national levels and prompted various educational reforms, such as revised curricula that make schools accountable for providing opportunities for students to develop digital competence (for digital competence in the Nordic context, see, Erstad et al., 2021;Godhe, 2019). Søby (2015) argues that educational research has increasingly drawn attention to digital competence in such a way that it has made it a shared focus of research and policy-making. Conversely, reviewing articles published between 2005 and 2013, Ilomäki et al. (2016) conclude that digital competence is a relatively new interdisciplinary term in educational research. However, they also suggest that digital competence "operates as a loosely defined boundary concept (. . .) amongst policymakers, practitioners and researchers" (Ilomäki et al., 2016, p. 657). Subsequent reviews have given a similar picture of the concept as elusive and inadequately defined (e.g., Spante et al., 2018). This ambiguity has resulted in extensive discussions about how to conceptualise digital competence and what skills and abilities should be included in the term, especially in education where the question of what knowledge students must develop is essential (Erstad & Voogt, 2018). While students' digital competence has been foregrounded in policy documents, formulations about teachers' competence in preparing and supporting students for participation in a digitalised society have been relegated to the background or omitted altogether. An assumption discussed is that the emphasis on digital competence has implications that are more comprehensive, complex and demanding for the teaching profession than for other professions (Blau & Shamir-Inbal, 2017;Carpenter et al., 2020;Howard et al., 2021;Novella-García & Cloquell-Lozano, 2021;Uerz et al., 2018). For teachers, digital competence implies, for example, that in addition to being able to use the technology themselves, teachers are required to meta-reflect on technology use in relation to pedagogy and what it can mean for students' learning in specific contexts (Sanders & George, 2017).
To date, research within the educational research field has investigated TPDC from various theoretical and methodological perspectives. The findings suggest a range of shortcomings in the digital competence of teachers working at different levels in the school system. Studies in higher education research (Spante et al., 2018) have highlighted these shortcomings in relation to teacher students' preparedness for teaching with digital technology (e.g., Helleve et al., 2020;Howard et al., 2021;Lund & Aagaard, 2020), teacher educators' professional digital competence (e.g., Carpenter et al., 2020;Instefjord & Munthe, 2017;Krumsvik, 2011Krumsvik, , 2014Lund et al., 2014;Uerz et al., 2018) and in-service teachers' development of digital competence and attitudes towards technology (e.g., Björk Gudmundsdottir & Hatlevik, 2018;Pongsakdi et al., 2021;Starkey, 2020). One way to uncover and delineate what competences teachers need for teaching in digitalised classrooms has been to develop different frameworks, for example, the comprehensive DigCompEdu (European Commission, 2021), ICT competency framework for teachers (UNESCO, 2021) and TPACK. 1 The latter is developed by Mishra and Koehler (2006) and identifies the three following knowledge areas: 1) technological, 2) pedagogical and content and 3) the integration of these. As well as constituting a conceptual framework, TPACK has been used to empirically study how these knowledge areas are enacted in specific teaching contexts, which has contributed to understandings of the numerous factors that play into teachers' work in the classroom (e.g., Pareto & Willermark, 2019). Thus, a general tendency in educational research has been for studies to report on teachers' limited ability to integrate technologies into their teaching in a way that extends beyond the sporadic use of digital tools (e.g., Lund & Aagaard, 2020;Novella-García & Cloquell-Lozano, 2021;Sanders & George, 2017).
Such shortcomings are often based on the critique that digital competence as content has been neglected in both teacher education and professional development efforts. Another reason for the strong emphasis in research on teachers' insufficient digital competence, Rice (2021) maintains, is the positioning of teachers as "inherently anxious and/or resistant" (p. 524) regarding technology integration. However, Selwyn (2011) claims that the digitalisation of schooling cannot be understood only from the perspective of teachers' shortcomings but should be discussed from a holistic perspective that takes into consideration education's role in society and the many actors involved at different meso-and macrolevels. In his critical analysis, a lack of "direct correspondence between the interests of school authorities, policy-makers and IT firms and the micro-level behaviours of teachers and students" emerges (Selwyn, 2011, p. 103), and this discrepancy between levels adds to the complexity of teachers' professional digital competence and classroom teaching.
Previous reviews of empirical studies have provided the field of education with valuable knowledge (e.g., Ilomäki et al., 2016;Spante et al., 2018;Starkey, 2020;Uerz et al., 2018). The aim of this paper is to expand knowledge by examining conceptualisations of TPDC in studies that primarily focus on active teachers in the school system. Such in-depth analysis can serve as a frame of reference for discussions in research as well as with stakeholders and practitioners concerning TPDC in twenty-first-century school systems. At a general level, there is a need to acknowledge the numerous concepts used to describe teachers' competence and skills in relation to digital technology to be able to critically discuss this slippery, elusive concept. Other than digital competence, commonly used concepts in the literature are, for example, digital literacy, media literacy, media competence, computer competence and information and technology competence. This plethora of terms appears in various discourses, including ongoing debates in politics, research and the media (Falloon, 2020;Søby, 2015), and their meanings seem to partly overlap (for a thorough review of the terms used and their implications, see, Ilomäki et al., 2016). Thus, TPDC is not the most commonly used concept, though it is slowly being established in educational research. In this overview, we will use TPDC as an umbrella notion to discuss the characteristics of the conceptualisations included in the selected publications, to point to specific prominent aspects of TPDC and to distinguish aspects that are less prevalent or absent.

Aim
This literature overview examines the concepts related to TPDC as they are used in the literature in educational research between 2010 and 2019 to create a platform for future discussions and strategic developments. More precisely, it aims to scrutinise if and how the concepts addressing TPDC are conceptualised in terms of 1) variations in the terminology used, 2) whether they are based on definitions from policy and/or research and 3) what aspects of teacher competence they include.

Methods and materials
Following established recommendations and transparency in the search process, this literature overview builds on specific search procedures in selected databases. It draws particularly on the following eight procedural steps outlined by Gough (2007): 1) conduct a brief scoping review to obtain an overview of the functionality of the keywords in the existing literature; 2) elaborate the keywords; 3) define inclusion and exclusion criteria; 4) articulate a search strategy and choose information sources; 5) screen the publications based on the inclusion/exclusion criteria (here by using the web-based application Rayyan); 6) add further relevant publications by the chain referral sampling method; 7) map the results of the search strategy; and 8) interpret and synthesise the conceptualisations found in the included publications. Below, we describe in more detail how the overview work was conducted.

Database selection, the search process and criteria for inclusion and exclusion
As they were relevant for our purposes and providers of national and international educationrelated journals, the following two databases were used in this literature overview: Academic Search Complete and Education Research Complete (EBSCOhost) and Education Resources Information Center (ERIC). To obtain an overview of the existing literature, a brief scoping review of the field for concepts of TPDC was conducted in the two databases. The search retrieved an insufficient number of relevant publications, which provided insight into the complexity of the topic. Therefore, to identify conceptualisations of teachers' abilities and skills in using digital tools and media in education, broader search terms were included. The following three sets of search terms were used: (i) ("digital competenc*" OR "digital literac*" OR computer literac* OR computer competenc* OR media literac* OR media competenc*) (ii) AND teacher* (iii) NOT (college OR "higher education" OR "teacher education" OR "pre-service teacher") We delimited the search in several ways. The first set of terms was limited to abstracts and keywords in the search box Select a field (optional). The second and third sets of terms were subject to the search option Apply equivalent subjects. For the inclusion of related concepts and the exclusion of other domains, such as higher education and teacher education, the expanders OR and NOT were used to combine keywords. To narrow the search, both parentheses and quotation marks were used to encapsulate word units, and the limiter AND was used to confine the search to teachers as a category. The purpose of the delimitations was to emphasise publications that focus on practicing teachers in the school system. To limit the results, we only included peer-reviewed journal articles written in English and published between 2010 and 2019. The search was conducted in February 2020. The decision to restrict the search to publications from the last 10 years was made to capture the most recent concepts, contribute to current discussions in research and policy and provide a more focused and up-to-date overview.

Selection procedure
Initially, 184 publications met the inclusion criteria. These were transferred to the software program Rayyan 2 which was used to sift out irrelevant publications. Two duplicates were found, leaving 182 publications (see, Figure 1 for a flowchart of the selection process). Before the manual selection work began, the four authors met to elucidate the criteria for decisions on inclusion and exclusion to ensure a shared understanding. Concretely, this was done through a joint screening of the first 10 abstracts. Thereafter, each abstract of the 182 publications was read by two authors (that is, each of the four authors read 91 abstracts) to secure inter-rater reliability. The first screening by the two pairs of authors resulted in a consensus to include 23 abstracts and exclude 45 abstracts (the exclusion reasons were mainly a focus on students' digital competences in the abstracts and, in a few cases, on media education). The remaining 114 abstracts became subject for further discussion since at least one author had marked them in Rayyan as of uncertain relevance (62) or the program indicated conflicting inclusion decisions (52). Jointly, all four authors reached an agreement, which resulted in 105 exclusions and 77 inclusions of publications at this stage. In the next step, the 77 publications were transferred to a data charting form that was designed with the following 15 pre-set columns: 1) inclusion/exclusion of a publication; 2) author/s; 3) year of publication; 4) journal; 5) country; 6) aim; 7) method(s)/sample/context etc.; 8) theory; 9) conceptualisation of TPDC by research; 10) conceptualisation of TPDC by policy; 11) conceptualisations of TPDC by both research and policy; 12) no definition of TPDC; 13) interesting issues found in the publication; 14) exclusion reasons; and 15) potential articles referred to in the publications that are included by the chain referral sampling method.

Data analysis
The data analysis started with the 77 publications being evenly distributed among the authors for a careful full-text reading. The content was documented in the chart form according to the columns presented above, and uncertainties in the assessment were marked in yellow to be discussed among the authors. After the first round of reading, 27 publications were excluded as they were not published in journals included as authorised publication channels in the Norwegian Register for Scientific Journals, Series and Publishers (NSD), 3 which left us with 50 publications. In our further search for conceptualisations of teachers' digital competence, the decision was made to carry out a second analysis of the chart and the columns of definitions to examine how the remaining 50 publications explicitly addressed teachers' technology use in education. An important finding at this stage was that concepts such as digital competence, digital literacy or computer literacy were not further explained or defined in the full text even though they appeared in the publications' abstract, title or keywords. This analysis resulted in 36 excluded publications, which left us with a corpus of 14 publications. Subsequently, the list was expanded based on the chain referral sampling method  (Biernacki & Waldorf, 1981), with four publications referred to in some of the 77 publications and found in key journals being added. These four publications were read by the first author. The final corpus for this overview thus amounts to 18 publications (see Appendix 1).
To prepare for further analysis of the conceptualisations, a table (see Appendix 2) was created, which included the 18 publications. The table contains the authors of the publications, the study design and terms used to describe teachers' competence and the foundation of the conceptualisation. After scrutinising the corpus, the following seven aspects addressing teacher professional digital competence were identified: 1) technological competence, 2) content knowledge, 3) attitudes towards technology use, 4) pedagogical competence, 5) cultural awareness, 6) critical approach and 7) professional engagement.

Findings
In this section, we present an in-depth analysis of the 18 publications included in the corpus, reporting first on the scarcity of conceptualisations addressing TPDC found in this overview. We then provide a brief descriptive framing of the publications in terms of distribution and methods, followed by an outline of definitions or descriptions of the various identified concepts and their foundations. Finally, we account for the seven aspects related to TPDC that we found in the data regardless of terminology.
To understand how TPDC is discussed in the publications in relation to school context and society, we have been informed by the holistic approach presented by Selwyn (2011) and the ecological system theory outlined by Bronfenbrenner (1979Bronfenbrenner ( , 1986. Selwyn (2011) specifically addresses how the implementation of technology in schooling operates at macro-, meso-and microlevels. In turn, the theory Bronfenbrenner (1979,1986) proposed is commonly used to understand the interplay between individual or collective learning and development in processes of reciprocal interaction within surrounding social systems and more distant societal structures. Important to our analysis is the idea that systems do not operate at different isolated levels but are integrated in a dynamic ecological way in that they influence and are influenced by the acts of individuals and groups within and between the systems. Bronfenbrenner (1979) identified five systems: micro-, meso-, exo-, macro-and chronosystems. In our analysis of the conceptualisations included in the corpus, we adopt this ontological approach and account for the identified TPDC and the seven aspects as operating within these five systems as follows: 1) microsystems, in which teachers' competence is mostly described as an individual effort; 2) mesosystems, in which teachers' competence is diversely described, from being an individual effort to an interactive matter that involves other teachers and the school context; 3) exosystems, in which more remote systems influence individual teachers' work or collective work, such as the regulations and edicts of a municipality, culture and research; 4) macrosystems, in which teachers' competence and work are influenced by the overall political objectives of the educational system, policies, teacher education and research; and 5) chronosystems, which are described as involving collaborative awareness of competences as continuously shaped by socio-historical and socio-technological changes over time.

The scarcity of conceptualisations
In the review process, two particularly significant characteristics of the literature were noted. First, the analysis revealed that more than half of the publications (n = 105) took a student perspective on digital competence, although various concepts relating to TPDC were included in the abstracts or keywords. In the second stage of the review process, when only publications that specifically focused on TPDC remained, we found that almost 75% of the publications (n = 36) did not provide clear definitions or descriptions of the terms used (see, Figure 1). Thus, the scarcity of conceptualisations became apparent, and consequently, most of the publications identified through the database search were excluded from further analysis.

Descriptive framing
The 18 included publications represent a diversity in terms of country of origin and methods. Geographically, three regions are represented: Europe, Africa and Asia. However, most originate from Europe (n = 14) and particularly from the Nordic countries (n = 6), with Norway contributing four publications. Africa is represented by three studies, two from Nigeria and one from Morocco. Finally, one publication comes from Iran (see Appendix 2). In the studies, questionnaires are the most commonly used method (n = 11) to investigate issues such as teachers' use of or influencing factors on ICT in education or teachers' beliefs and attitudes towards digitalisation (Aznar & González, 2010;Badia et al., 2014;Benali et al., 2018;Eyo 2016;Krumsvik et al., 2016;Ouma et al., 2013;Tomczyk, 2019;. One publication is based on teacher interviews (Xerri & Campbell, 2016), and three others use a mixed-method design comprising questionnaires, interviews and/or classroom observations Olofsson et al., 2019;. Another publication consists of a text analysis , while another is a discussion paper on the concept of digital competence . One publication constitutes a literature review (Pettersson, 2018). In sum, to a large extent, the publications in our corpus base their results on self-reported material, and few analyse teacher-student interactions in digitalised pedagogical contexts.

The concepts and their foundations
Several concepts that address TPDC appear in our corpus (see Appendix 2), such as digital competence 4 (n = 11), digital literacy (n = 4), ICT competence (n = 1), computer competence (n = 1), and media competence (n = 1). Moreover, it was found that these conceptualisations are grounded in research (n = 8), policy-related texts (n = 1), or both research and policy (n = 8). One publication does not refer to any source. The publication referring only to policy employs the concept of digital competence, and the one without reference to research or policy uses digital literacy. In the following, we provide an account of each of the concepts and their foundations.

Digital competence
As mentioned previously, in educational research, the concepts of digital competence and digital literacy are often used interchangeably, even synonymously (Ilomäki et al., 2016). In our corpus, one publication was found to apply both concepts when addressing TPDC as a "notion in motion" (Johannesen et al., 2014, p. 300). In their discussion, Johannesen et al. (2014) draw on researchbased, general definitions of digital literacy as well as teachers' digital competence. They also refer to policies, particularly the national curriculum and its formulations on students' digital competence, as a starting point for their proposal on what TPDC should contain, which is the following: 1) teaching of ICT, that is, teaching students how to handle technology; 2) teaching with technologies, encompassing "the pedagogical idea of using technology for learning" in all subjects; and 3) teaching about ICT, which involves teaching the historical development of digital technology, its cultural role in democratic societies and critical thinking (Johannesen et al., 2014, p. 309). Similarly, describing the concept of digital competence as specified both in national and international policies,  states that teachers "must be able to use technology in their own teaching so that they can help students to manage the digital competence aims in the curriculum" (p. 558). In addition,  considers research in constructing the hypothesis that teachers' beliefs and confidence in using digital technologies correlate with their capability to teach and support students' digital competence. Teachers' attitudes to technology are analytically understood as a significant part of the author's conceptualisation. Building on his early definition that also was based on policy and research, but not included teachers' perceptions, Krumsvik et al. (2016) suggest that teachers' digital competence comprises "the individual teacher's proficiency in using ICT in school with good pedagogic judgment, and his/her awareness of its implications for learning strategies and the digital Bildung 5 of pupils" (p. 147). This definition 6 serves as the foundational concept in a later project investigating the digitalisation of the Norwegian school system, as well as for a model for the TPDC developed within the project . The model encompasses teachers' elementary and basic digital skills, didactic ICT competence, learning strategies, digital Bildung and gradual appropriation and increased self-awareness of these aspects, described as teachers' "mental digital competence journey" (Krumsvik et al., 2016, pp. 148-149). In the fifth publication in our corpus, Aznar and González (2010) base their rather vague conceptualisation on a student perspective, suggesting that to support students' development following the curriculum, teachers need to know and develop "the interactive tools and the innovative strategies that make this learning process easier for the students" (p. 181), thus acting as "facilitators of the cognitive scaffolding" (p. 184).
The conceptualisations of TPDC reported so far are formulated at an individual level (micro), although they relate to various policy-related texts governing specific educational intentions on the macrosystem level. As well as linking the micro and macro levels in their understanding of TPDC, Olofsson et al. (2019) draw attention to the mesosystem by observing how the concept of adequate digital competence, as described in the Swedish national strategy for the digitalisation of the school system (Swedish Association of Local Authorities and Regions, 2021), is interpreted and enacted by teachers in the classroom. Informed by their findings, previous research and frameworks such as the DigCompEdu, 7 Olofsson et al. (2019) conclude that teachers demonstrate and enact adequate digital competence in relation to "(a) technological challenges, (b) technologicalpedagogical challenges, (c) CPD [continuous professional development] and challenges related to time, identifying needs and networks and (d) technology-mediated communication and administration" (p. 13). This conceptualisation appears to be broader than the others as it includes contextual factors significant for all aspects of the teaching profession. Two publications included in the corpus highlight that TPDC must be understood in relation to the educational system since teachers operate within a system governed by school leadership and policy documents and conditioned by, for instance, traditions and digital infrastructure (Pettersson, 2018;. Despite arguing for a holistic perspective, Pettersson (2018) refers to researchbased definitions that address pedagogical aspects of digital competence on an individual level, such as Krumsvik et al. (2016), mentioned above. Similarly,  start from a micro-level understanding of TPDC when designing a survey targeting school leaders, teachers and students. They propose that TPDC specifically includes operational skills (such as the use of a word processor and ability to edit digital photos and texts), social media skills (participation in online discussion forums and social networks) and skills in "safe and responsible Internet use" (Wastiau et al., 2013, p. 12).
The DigCompEdu framework is referred to in three of the included 18 publications (Benali et al., 2018;Olofsson et al., 2019). Particularly, Caena and Redecker (2019) describe the framework as building on robust research as well as input from experts, policymakers and teachers. In DigCompEdu, TPDC is divided into the six following competence areas: 1) professional engagement, 2) digital resources, 3) teaching and learning, 4) assessment, 5) empowering learners and 6) facilitating learners' digital competence. Each area is then specified into three to five elementary competences. According to Caena and Redecker (2019), the framework can be beneficial on different levels: "At the micro-level, it can support and guide teachers' practice and continuous professional development. At the meso level, (. . .) it can support the development of school institutions as learning organisations (. . .), providing common ground for dialogue, collaboration and reflection. At the macro level, (. . .) it can provide reference standards for initial teacher education, and for education professionals' quality" (p. 356). Based on the six competence areas identified, a self-reflection instrument for teachers has been developed and an adapted version of this tool was used by Benali et al. (2018) in a study that measured the relationship between teachers' gender, teaching experience and confidence using digital technology. The conceptualisation offered by DigCompEdu apparently contributed to their understanding of TPDC as operating at the microsystem level. However, Benali et al. (2018) also draw on research and the TPACK model, mentioned in the introduction, in which TPDC is described as located at "the intersection of three primary forms of knowledge: Content (CK), Pedagogy (PK), and Technology (TK)" (p. 101). The authors further describe TPDC as influenced by personal factors, such as attitude to technology. Another publication (Eyo, 2016) builds on previous research findings indicating that TPDC is, to a certain extent, predicted by individual demographic aspects, such as gender and age. When examining teachers' use of social networking sites in teaching, these variables were included in the survey design. Eyo (2016) offers no distinct conceptualisation of TPDC, however, he uses categories in the analysis, such as technical handling, navigation of the internet and interaction with students, that indicate an understanding of TPDC operating within mesosystems.

Digital literacy
Four of the 18 publications employ the concept of digital literacy and refer to previous research to varying degrees. They also differ in how specifically they define the concept. In a study,  describe a collaborative project (DigiLit Leicester project) with teachers in which a common conceptual understanding of digital literacy was crucial for developing a self-evaluation framework. Part of the definition indicates that teachers' digital literacy involves "skills, attitudes and knowledge required to support learning in a digitally-rich world" (Hall et al., 2014, p. 5). Tomczyk (2019) provides a similar conceptualisation that also includes teachers' ability to "engage ICT in teaching a given subject" (p. 170). Both  and Tomczyk (2019) highlight teachers' skills to use different devices, applications and websites to change classroom practice, both pedagogically and socially. In addition, they include aspects such as personal and professional development via colleagues and media networks and the ability to "think critically about why, how and when technology supplements learning and teaching" (Hall et al., 2014, p. 5) and the "safety use of electronic media" (Tomczyk, 2019, pp. 170-171), which implies awareness of the existing threats on the internet, such as cyberbullying and piracy. Analytically, the two definitions can be understood as being formulated at all system levels as they orient towards the individual (micro), the school context (meso), the municipality context (exo), the societal context (macro) and changes over time (chrono).
The two other publications present limited conceptualisations of digital literacy. Badia et al. (2014) do not provide an explicit definition but refer to researchers who have found that teachers' belief in ICT, attitude and confidence are decisive for the extent of their ICT use. Without providing any references, Xerri and Campbell (2016) narrowly define digital literacy as "the knowledge and skills required to use a range of digital devices" (p. 396).

Computer competence, ICT competence and media literacy competence
In the corpus, three additional concepts are used to address TPDC: computer competence , ICT competence  and media literacy competence . The concepts are all based on research from different scientific fields and are defined in varying degrees of detail. For Ouma et al. (2013), technical competence and the individual teacher's ability to "select critically the right media in learning process" as well as more generic characteristics, such as teachers' attitudes and teaching styles, are central to ICT competence (p. 100). Both individual technical skills and attitudes are also mentioned by Fatemi Jahromi and Salimi (2013) as aspects of computer competence when reporting on a study investigating teachers' attitudes towards computer-assisted language learning. The authors suggest that "Educators need to acknowledge the influence of culture on every aspect of teaching and learning" (Fatemi Jahromi & Salimi, 2013, p. 161), indicating an understanding of TPDC within wider mesosystems.  likewise presents an individual perspective, drawing on media research and the broader concept of media literacy, which is described as "multi-layered, as it encompasses an individual's multidimensional competences" (p. 72), such as "technical competence, knowledge management skills, competence to make one's own decisions and democratic competence" (p. 70). The inclusion of democratic competence in this description may point to a conceptualisation that also takes into account broader systems.
To summarise, the majority (n = 7) of the 11 publications that use the concept of digital competence refer to both policy and research as a foundation for their conceptualisations. The curriculum and mission to support students' digital competence development forms the primary background for how individual TPDC is understood. This means that even if aspects crucial for understanding TPDC are discussed at macro and meso levels, such as contextual factors, the main accountability for developing digital competence still rests with individual teachers. The four publications that use the concept of digital literacy all refer to research. While they discuss teacher digital literacy from an individual perspective, two also take into account the contexts of school and digital networks. The three publications that use the terms computer competence, ICT competence and media literacy competence all base their conceptualisations on previous research, and the concepts seem to be understood on an individual level and, to some extent, in relation to wider mesosystems.

Aspects of TPDC
So far, the concepts related to TPDC, as they appear in the corpus, have been presented separately. Through a deeper analysis of all conceptualisations, we can distinguish seven recurring aspects that are highlighted in the publications regardless of terminology. The seven identified aspects of TPDC are 1) technological competence, 2) content knowledge, 3) attitudes to technology use, 4) pedagogical competence, 5) cultural awareness, 6) critical approach and 7) professional engagement. In the following, we report on these aspects separately to distinguish their specificities. However, as with all categorisation work, in the literature, the aspects are not always distinct but partly overlap.

Technological competence-within microsystems
Most of the publications (n = 15) addressed TPDC as a set of basic technological skills, which is not surprising as "any definition of digital competence must include basic skills in using digital tools" (Johannesen et al., 2014, p. 303). What emerges, however, is that technological competence is usually discussed within microsystems as something that applies mainly to teachers' handling of digital technology and concerns the individual teacher alone. Aznar and González (2010) and Ouma et al. (2013) argue that teachers are expected to have basic skills in both hardware and software to be able to manage various digital resources. Krumsvik et al. (2016) point to a distinction between elementary skills and basic skills. Elementary skills include generic operational skills, such as turning a computer or an iPad on and off or using a word processor, whereas basic skills are teacher-specific, such as handling "digital learning platforms and digital teaching aids attached to the curricula" (Krumsvik et al., 2016, p. 147). With a similar line of reasoning,  and  acknowledge that in addition to being able to use digital technology for their own purposes, teachers need to master educational technology. The publications in our corpus provide further examples of basic skills required of teachers, such as browsing (Badia et al., 2014;Tomczyk, 2019), retrieving, storing, producing, presenting and exchanging information , and communicating on social networking sites (Eyo, 2016). Because the range of programs and applications is vast, teachers need to have skills in finding and selecting appropriate resources and making modifications in relation to specific content and learning goals . Olofsson et al. (2019) also note that teachers need skills to solve technical problems that may occur in the classroom. Personal access to digital technology in schools is clearly a prerequisite for teachers to develop their technical competence . Limited or no access to IT at work may result in teachers doubting their competence in handling such technology (Xerri & Campbell, 2016).

Content knowledge-within microsystems
Only a few of the publications (n = 6) mention content knowledge as part of TPDC, which is remarkable as a core task for schools is to develop students' subject knowledge. Three publications explicitly highlight content knowledge and discuss this aspect within microsystems, as enacted by individual teachers in their classrooms, similar to technological competence, discussed above. For Johannesen et al. (2014), teaching with digital technologies implies "using technology carefully and systematically in the teaching of all subject areas at most times" (p. 309). This accords with , for whom TPDC comprises subject-didactic competence, "when they [teachers] apply their digital competence to subjects" (p. 84). These two conceptualisations, likely stem from the Norwegian curriculum, which states that digital technology should be included in all subject areas. Moreover, in defining digital literacy, Tomczyk (2019) states that subject knowledge and taking advantage of technology to create and teach certain content is a crucial ability for teachers. Content knowledge as an individual teacher competence is further addressed, albeit rather implicitly, in Fatemi , who discuss language teaching in relation to computer competence. Aznar and González (2010) vaguely elaborate on the knowledge domain of information searching as content, and Vodopivec (2011) discusses the necessity for teachers to integrate media into the teaching of the subject of media.

Attitudes to technology use-within micro-, meso-and exosystems
In 10 publications, teachers' attitudes to digital technology are identified as a factor that influences how and to what extent they use their digital competence in the classroom to support students' learning. Teachers' self-efficacy, that is, how they perceive themselves as technology users  as well as their confidence appears to play a crucial role in their attitudes Ouma et al., 2013;. Moreover, factors that affect teachers' attitudes towards technology use include years of teaching, gender and infrastructure (Benali et al., 2018). Fatemi  also suggest factors such as "access to IT in school, quality of technical support", "professional development in IT" and "cultural relevance" (p. 161). Negative emotion due to a lack of experience (Xerri & Campbell, 2016) and computer anxiety or computer liking (Badia et al., 2014) are examples of a personal approach that can contribute to negative or positive attitudes towards technology use. Tomczyk (2019) states that a techno realist, in contrast to a techno optimist, ignorant or pessimist, is a teacher who has "the optimal attitude of balanced evaluation of the positive and negative consequences of implementation ICT in the education process" (p. 169). Based on such conceptualisations, the publications discuss teachers' attitudes to technology use both from an individual and interactive perspective and within micro-, meso-and exosystems. On the one hand, teachers' attitudes are attributed to their individual capabilities and emotions, and on the other hand, these attitudes are related to the teachers' various surrounding social and cultural contexts, such as schools' practices. Teachers' engagement in these different social and cultural systems influences the experiences they have, which in turn shape their attitudes regarding technology use.

Pedagogical competence-within mesosystems
The majority of the publications (n = 16) highlight pedagogical competence as central when addressing TPDC. At a general level, this aspect involves teachers' knowledge and awareness of when and how to integrate digital technology into teaching in ways beneficial for students' social and cognitive needs and ability to achieve learning goals (Badia et al., 2014;Eyo, 2016;Pettersson, 2018;Tomczyk, 2019). This conceptualisation of pedagogical competence is analytically seen as operating within interactive mesosystems as it involves teachers' pedagogical and relational competence in relation to students. Accordingly, teachers need to be able to make pedagogical-didactic judgements, produce wellconsidered strategies and be confident in how different technologies can expand and deepen students' learning (Benali et al., 2018;Krumsvik et al., 2016). The pedagogicaldidactic judgements include everything from planning and designing  to organising subject-specific learning activities in digital classrooms . Such judgements imply, for example, the ability to critically select and use apps and other tools appropriately (Tomczyk, 2019). As digital technology develops rapidly, the conditions for digitalised schooling are also continually changing. The rapid pace of change requires teachers to have an ability to monitor the market supply , stay up-to-date and innovate teaching methods based on new technology (Aznar & González, 2010). An example of such an innovative teaching method, mentioned by Krumsvik et al. (2016), is the flipped classroom.  refers to staying up-to-date as research-pedagogic media competence. According to Caena and Redecker (2019), pedagogical competence also includes competence in analysing student data generated via various digital platforms.

Cultural awareness-within mesosystems
Five of the 18 publications in the corpus point to the importance of the cultural context or teachers' awareness about culture in relation to teaching and learning with digital technologies. This aspect of TPDC is discussed within interactive mesosystems, in the sense that both culture (e.g.,  and the social conditions within the local school setting influence the thinking and actions that take place in the digitalised classroom . For example, to support students' digital Bildung, teachers in their teaching need to have both a broad perspective on the general technological development and its social and cultural significance for society , and a narrow perspective targeting how their students "grow and develop their identity" across digitalised contexts (Krumsvik et al., 2016, p. 151). With this in mind, we argue, that TPDC should be regarded not as "an isolated phenomena" but as "influenced and driven by several contextual factors embedded within and across a wider school organization" (Pettersson, 2018(Pettersson, , p. 1005).

A critical approach-within micro-, meso-and macrosystems
A critical approach is included in the conceptualisations relating to TPDC in seven of the publications. Analytically, this aspect is considered to overlap with pedagogical competence and is discussed within micro-, meso-and macrosystems. Some authors take an individual teacher perspective in their conceptualisations, while others focus on the teaching profession as a collegial collective. From an individual perspective, Ouma et al. (2013) argue that teachers need to be critically competent when selecting appropriate digital technologies for teaching, and  pinpoints that teachers' individual opinions about technologies and behavioural patterns when using technologies should involve a critical approach. In , teachers' critical qualities can also be seen as operating mostly within individual microsystems as TPDC is understood as teachers' comprehensive digital responsibility throughout the process of involving technology as part of teaching. A more interactive stance is taken by , who suggest a critical use of digital technology in communication with others. Tomczyk (2019) similarly emphasises critical awareness and judgment in interaction with others regarding the implications of using technology in education.
In two of the 18 publications, a more permeated critical approach appears involving futureoriented, transformative qualities Hall et al., 2016). Caen and Redecker (2019) highlight "the importance for teachers to individually and collectively reflect on their teaching practices, to critically assess the effectiveness and appropriateness of their digital teaching strategies" (p. 363). Such transformative qualities are also invoked by  and  regarding the importance of teachers reflecting critically not only on why, how and when technology supplements teaching and learning but also on their own opinions about technologies and how digital technology can enrich professional identity and growth. Thus, a critical approach in the conceptualisation of TPDC operates partly within individual microsystems but also within interactive macrosystems that entail a holistic and conscious view of the role of technology both in education and society more generally.

Professional engagement-within micro-and chronosystems
Besides teaching, teachers' work consists of tasks such as administration, communication with caregivers, collegial discussions and competence development. In line with the DigCompEdu framework, we refer to this aspect of TPDC as professional engagement. Nine publications discuss the aspect from different points of view, as operating both within individual microsystems and within what Bronfenbrenner (1979Bronfenbrenner ( , 1986 refers to as interactive chronosystems as it is forwardlooking, collaborative and prone to development. In her review, Pettersson (2018) found evidence of the former view and that it exists "an underlying, or even normative, assumption that teachers are responsible for developing their own digital competence to meet the needs of students in digitalized schools" (p. 1016). However, following Pettersson (2018), we argue that TPDC should not only be an individual concern but should also operate within interactive chronosystems on an organisational level; it, therefore, demands strategic leadership.
In DigCompEdu, professional engagement is described partly as a communicative competence that encompasses the ability to collaborate and interact with colleagues, students, caregivers and other stakeholders in an appropriate way via digital resources , such as email and other administrative systems . In Olofsson et al. (2019), professional engagement involves teachers' competence not only to establish solid networks and be creative in their communicative strategies but also to be able to formulate their own needs for professional competence development, such as how to effectively integrate new teaching technologies . This implies an individual awareness of what kinds of skills and proficiencies are needed and individual responsibility for one's professional development (Xerri & Campbell, 2016). Four publications suggest that this individual ownership of competence development can be attained through active participation in online collaborative networks, such as teacher-specific social media groups, which involves communicative and technological competences that should be included in TPDC Tomczyk, 2019;.

Discussion
In this overview, we set out to investigate if and how TPDC has been conceptualised in the literature in the field of education between 2010 and 2019.

The absence of pronounced conceptualisations of TPDC
In reviewing the literature, we found that the concept, or related concepts, was frequently mentioned in abstracts, keywords and full texts, but to a large extent, it was rarely described in detail. The authors of the publications seem to presuppose the meaning of the words, which means that there is no need for elaboration. A further note made in our reading is that TPDC specifically is often not clearly distinguished from, and is recurringly confused with, the more general term digital competence, which in most cases refers to students' digital competence. The findings align with Pettersson (2018) who has pointed out, "the meaning and scope of digital competence and its related concepts (. . .) seem seldom to be well-defined and are often used as synonyms when describing the competences needed for actors working in educational contexts" (p. 1015). We suggest that adopting different conceptualisations for digital competence and the more teacher specific competence, certainly would be beneficial for an ongoing and valuable discussion (cf., Ilomäki et al., 2016;Krumsvik, 2011). Although many previous reviews of the literature have made valuable attempts to conceptualise digital competence (e.g., Falloon, 2020;Ilomäki et al., 2016;Spante et al., 2018;Uerz et al., 2018), they have tended to pinpoint varying aspects that rarely bring us closer to a clear notion of the term. As the concept is characterised in research as elusive, multidisciplinary and complex (i.e. Erstad et al., 2021;Johannesen et al., 2014), we found it surprising that limited efforts have been made in empirical studies within the field of education to clarify what the concept means and thus to contribute to its development.
As shown in the findings section, only 18 publications remained for further analysis after our exclusion criteria were applied. In this corpus, digital competence was the most widely used concept, which confirms previous findings showing that the concept is becoming increasingly central in the research literature (cf., Ilomäki et al., 2016;Søby, 2015). We also found that several publications built their conceptualisations of TPDC partly on policy-related documents that focus on student achievement goals. At first glance, this indicates that the understandings of TPDC become very general. We argue that it can be problematic to base TPDC on educational goals for students, derived from political directives formulated far from the school practice and classroom teaching. As Selwyn (2011) reminds us, the integration of digital technology and the "micro-level behaviours of teachers and students" that follow imply "a highly contested and uncertain practice" (p. 102-103). That is, regarding the classroom as a social, cultural and situated pedagogical practice where teachers and students negotiate meaning and act in resistance as well as conform to "the 'neo-liberal orders' that are associated with macro-and meso-level influences" (Selwyn, 2011, p. 102) has implications for TPDC that needs to be taken into account in its conceptualisation. However, we can also conclude that digital competence seems to function as what Ilomäki et al. (2016) call a boundary concept as the policyformulated concept is often used in empirical research.

Seven aspects of TPDC conceptualised within micro-, meso-and macrosystems
In the next analytical step, we scrutinised how TPDC is addressed in the publications that provided conceptualisations and we identified TPDC as comprising of seven aspects (technological competence, content knowledge, attitudes towards technology use, pedagogical competence, cultural awareness, critical approach and professional engagement). When analysing these aspects using the ecological systems framework (Bronfenbrenner, 1986), we found that five of them were discussed in varying degree as the competence of individual teachers. Technological competence and content knowledge mainly operate within microsystems, while attitudes towards technology use, a critical approach and professional engagement occur partly within microsystems. This focus in research indicates that teachers are positioned as individually accountable for their professional development (e.g., Olofsson et al., 2019;Tomczyk, 2019;Xerri 2016), instead of the responsibility being placed at an organisational level (cf., Pettersson, 2018;. In tune with this view, there also seems to be an assumption that teachers' appropriation and mastery of digital tools in teaching follow a linear process with discrete elements of effective technology use. Such view is often based on self-evaluations measuring quantitative patterns and levels of digital skills and techniques, which in turn results in linear professional development models (Rice, 2021). We adopt a critical stance on these models and instead, like Rice (2021) who advocate an "intraactive" model (p. 525), want to highlight teachers' agency and the social contexts as significant aspects for professional development. This reasoning is also interesting in relation to the increase in teachers' professional learning taking place outside formal in-service training in various online social media communities, which comprise a "continued predominance of development related to technology based teaching and other educational technology topics" (Lantz-Andersson et al., 2018, p. 311). Thus, we argue that this view of TPDC as based on the efforts of individual teachers is a dead end as school digitalisation, teachers' technology-based teaching and thus their competence, needs to be primarily the responsibility of the school leadership for achieving continuity and equality.
Similar to previous reviews (e.g., Carpenter et al., 2020;Helleve et al., 2020;Starkey, 2020;Uerz et al., 2018), our overview shows that pedagogical competence (n = 16) and technological competence (n = 15) are rather prominent aspects of TPDC. This finding also aligns partly with the framework of TPACK (Mishra & Koehler, 2006), in which pedagogical and technological competence are highlighted as two central knowledge areas for teaching in digitalised classrooms. However, the third knowledge area in the framework, content knowledge, was not as prominent as the other two in our corpus (n = 6). To us, such silencing of content knowledge in relation to TPDC in the literature is problematic as content should be the basis from which teachers plan their use of digital technologies in the classroom. A further thought given the result, the few publications that do not include technological competence when addressing TPDC, is that aspect taken for granted or is it embedded in the understanding without being emphasized? For Caena and Redecker (2019), technological competence seems to be included implicitly when presenting the EU DigCompEdu. They argue that the framework for educators builds on the general DigComp, which contains ICT competence, and that this aspect is thus assumed and omitted in the framework. However, we believe that technological competence and pedagogical competence should not be discussed separately, other than in research analysis, since in a classroom context, they are preferably intertwined. If technological competence in terms of elementary skills, such as "turning on a computer or an iPad and using a word processor" (Krumsvik et al., 2016, p. 147), is not discussed in relation to a specific content or pedagogy, the discussion becomes irrelevant as such elementary skills are not static and will likely, in a recent future, become, and may already be, self-evident. Instead, basic technological skills should probably involve finding innovative methods that include various programs, applications and websites that develop and support students' learning . Indeed, we argue that it is not possible to make clear-cut distinctions between elementary, basic and advanced levels of skills since teachers' appropriation and mastery of digital tools in teaching do not follow a linear process. Teachers can be both fluent users of a certain known digital technology and beginners in new ones.
The third most-mentioned aspect relating to TPDC in our corpus is the attitude towards technology use in teaching (n = 10). This finding aligns with a large body of research showing that teachers' attitudes and confidence are crucial to how they use technology in the classroom. Recent research provides evidence that in-service teachers' attitudes and confidence in implementing and using technological tools can be improved through digital pedagogy training. Pongsakdi et al. (2021) found that Teachers who had low confidence in ICT use showed an increased ICT confidence level after the programme, while teachers who already had high confidence in ICT use showed no significant changes in their confidence level. Moreover, the results indicated that the need for ICT support was lower after the training for the teachers in [the] high confidence group, while there were no significant changes in the need for ICT support for the teachers in the low confidence group. (p. 5041) This finding not only points to the importance of competence development efforts for teachers with lower levels of confidence but also indicates that such efforts cannot be seen as quick fixes; rather, it takes time to develop a teaching staff with high levels of confidence in technology use, and the responsibility for such continuous training lies at the school leadership level. This reasoning touches on another noted aspect of TPDC, namely professional engagement. In the publications that include elements of what we interpret as professional engagement, this aspect appears as something transformative and forward-looking that develops over time. On the one hand, the accountability for developing sufficient digital competence to perform teacher work seems to be placed on the teacher to learn individually and/or through collective resources off-and online. On the other hand, some authors advocate that responsibility should be shifted to actors at mesoand macrosystems levels, such as school authorities and politicians. We agree with the latter opinion; however, as teachers act in socially and culturally situated practices, they also have to be aware of their specific needs.
Other aspects of TPDC identified in our overview of conceptualisations are cultural awareness and a critical approach. The former is addressed in very few publications, which is at odds with research findings that highlight the significant role of culture for learning, of which teachers should be knowledgeable. For example, popular culture, as presented in various digital media, is one source for children's emergent literacy (e.g., Sefton-Green et al., 2016). Another relevant aspect of culture, highlighted by Fatemi , is the general perception in society of the role of digital technology for learning, which in turn has implications for teachers' access to and use of technology in the classroom. The other aspect, critical approach, overlaps with pedagogical competence to a certain extent. A critical approach is highlighted as important during the pedagogical process of planning and organising technology-mediating learning activities, as well as for supporting students in adopting a critical awareness about media content. Krumsvik et al. (2016), , and Johannesen et al. (2014) discuss this aspect in relation to digital Bildung, which is a contested concept closely connected to identity, attitude and a lifetime endeavour. In seeking to improve TPDC, researchers and policy-makers might consider how to support teachers to succeed in developing students' digital Bildung. There are further aspects of TPDC that our analysis did not uncover. Similar to what Novella-García and Cloquell-Lozano (2021) have noted, we did not observe an ethical dimension in the publications, which should constitute an underlying premise of TPDC based on the overall aim of education to prepare students for critical, tolerant and active participation in a digital and democratic society. We see a need here for future research that identifies other "silenced" aspects important for teaching, such as relational features, including teachers' interactions with students.

Limitations of the study
Our overview, like reviews in general, has several limitations, most of which are linked to the search procedures and inclusion/exclusion criteria. First, we only included peer-reviewed journal articles, thus excluding, for example, publications in conference proceedings, books and book chapters. Second, we also excluded publications on teacher education. Third, we only expanded our initial search using the chain referral sampling method (Biernacki & Waldorf, 1981), including references that appeared in our initial corpus. However, these limitations are also deliberate choices based on our interest in investigating how the concept of TPDC is defined and conceptualised in relation to active teachers in the compulsory school system. This approach made evident that the concept of TPDC and related concepts are frequently included in publications but are seldom conceptualised or elaborated upon. Instead, these concepts are used to signal an interest or a focus. Based on this result, we emphasise the importance of future empirical studies in education on the concept of TPDC not only to employ analytical acuity but also to contribute to a conceptual discussion and understanding of TPDC.

Conclusion
To conclude, when studied closely, the seven aspects of TPDC identified in the examined publications appear to be described, on the one hand, as individual abilities and, on the other hand, as collective and interactive abilities dependent on situated classroom contexts and on larger societal systems. Salient is that technological competence, which is the aspect most frequently discussed in the publications after pedagogical competence, is viewed as operating within individual microsystems, which indicates that the responsibility for developing technological competence in the literature is still considered a responsibility of individual teachers. This implies that the organisational level of school leadership is not held accountable for providing teachers with such competence. We argue that the conceptualisation of TPDC needs to be directed away from the strong focus on the technological competence and basic hands-on skills of individual teachers to a focus on a collective responsibility and accountability for TPDC, including by school leaders. Moreover, because teachers' professional digital competence operates within the chronosystem and interacts with socio-historical and socio-technical changes over time, critical, scientific and ethical competences need to correspond with changes in society to prepare students for an unknown future. In such an interactive and dynamic process, the meanings of TPDC must be continuously defined and redefined. Therefore, we argue for a conceptualisation of TPDC that is future-oriented and takes a transformative stance that leads to and is open to the opportunities and challenges that tomorrow's technology will bring.

Technological Pedagogical Content Knowledge:
A framework for teacher knowledge.
2. Rayyan is a web-based application that enables researchers to conduct reviews on an online spreadsheet and subsequently to work collaboratively with other researchers' suggestions regarding the inclusion and exclusion of publications. https://rayyan.qcri.org/ welcome 3. The NSD, also referred to as the Norwegian list, shows scientific publications that are recognised in the weighted funding model in Norway, which has also become an international standard in light of questionable, open-access scholarly publishers. https://dbh. nsd.uib.no/publiseringskanaler/Forside 4. One publication adds the prefix professional  and another adequate .
5. The concept of digital Bildung is included in the Norwegian curriculum and relates to students' confident and innovative use of digital technologies to achieve personal goals and active participation in a global society (Johannesen et al., 2014, p. 302). 6. The definition has received attention from other researchers in our corpus, such as Benali (2018), Johannesen et al. (2014), Olofsson et al. (2019), and Pettersson (2018). 7. The European Union framework for teachers' professional digital competence at all levels in the education system. https://op.europa.eu/en/publication-detail /-/publication/fcc33b68-d581-11e7-a5b9 -01aa75ed71a1/language-en# Appendix1 Included publications. Publications included by chain referral sampling method are marked with *