Today, the emergence of technologies, such as 3D Virtual Worlds (VWs), which provide realistic three-dimensional environments and offer engaging, interactive and immersive experiences, creates new opportunities for teaching and learning. During the past years, several researchers have recognized the educational potential of 3D VWs , . The most intriguing asset that 3D VWs offer for education is that they allow their users create their own artifacts collaboratively. The users using their avatars can create from simple objects, which in Second Life are referred as "prims", like for example a simple chair, to big buildings like for example Virtual Museums .
On the other hand, school teachers are beginning to realize that 3D VWs may become a valuable tool for them, as they give them and their students the opportunity to share those artifacts (projects, presentations, demonstrations and/or simulations) in the form of virtual objects, textures and/or notecards within a synthetic world that allows interaction, communication and collaboration activities. Moreover, using their avatars students are provided with the ability to interact with other users creations and also manipulate and/or reconfigure them .
Moreover, there are a number of studies , , ,  , ,  that have acknowledged the educational affordances of 3D VWs and examine the potential of using them in teaching and learning. However, several researchers , , , argue that 3D VWs are "empty spaces" that could become valuable for education if they are designed in such a way so as to support the design and the implementation of educational activities and not only the transfer of educational content in them. To this end, educational tools and applications which aim to integrate existing learning technologies (such as Course Management Systems) in 3D VWs infrastructure (such as Second Life(SL)) were developed .
On the other hand, school teachers must be encouraged to model effective use of technology in their own practices, taking into account the new opportunities that digital technologies such as 3D VWs offer. To this end, there have been research studies that focus specifically on teachers' experiences either through using 3D VWs in their teaching activities or through their participation in 3D VWs supported Continuing Professional Development (CPD) , , , , . These studies indicate issues, such as: a) the extra pressure applied to teachers who teach within 3D VWs, and b) the lack of understanding of the new possibilities offered by 3D VWs in teaching and learning. Thus, we should take into account that the possible use of 3D VWs is a major challenge for teachers, since they introduce new concepts that even teachers who are experienced and keen on using digital technologies are not familiar with . Based on the above it is indicated that there is a need for Teachers' CPD Modules and Programmes that aim to develop appropriate competences for real life teaching supported by VWs.
This problem was identified by the international community of researchers and in literature there are some specific educational and development projects that aim to design and develop applications that aim to integrate technologies that are already used to support teaching and learning (such as Course Management Systems) with the currently established infrastructure of 3D VWs (such as Second Life) , to devise competence profiles of teachers capable of teaching effectively within a 3D Virtual World , to design and organize training activities for teachers' CPD on the exploitation of 3D VWs for teaching and learning  and to design and develop 3D Virtual Learning Environments within 3D VWs in order to provide teachers with the best possible facilities to either use 3D VWs for teaching and learning or form online learning communities related to the exploitation of 3D VWs for education .
Within this context, in this study we will present our case for school teachers' training activities facilitated by a 3D Virtual Classroom Simulation (3D VCS) (designed and implemented using SLOODLE), as the means for simulating the familiar "traditional" classroom in the unfamiliar context of 3D VWs and thus, by presenting them in a module designed using the Synectics "Making the strange familiar" instructional strategy, we target supporting teachers understand these environments, explore their potential in enhancing their educational practices and acquire competences for teaching in them.
Objectives and Steps
The main objective of this study is to develop a module in Teachers' Continuing Professional Development programs that aims: a) to support teachers understand the concepts related to 3D VWs, b) explore the new possibilities that 3D VWs present for teaching and learning and c) equip them with useful competences for teaching within 3D VWs.
Thus targeting the above mentioned objective we have followed some specific steps. Step 1 - Identify the key concepts related to using 3D VWs and express them as their affordances for teaching and learning, Step 2 - Formulate a competence description proposal (novice level, competence level as proposed in ) for teachers being capable of teaching in 3D VWs, Step 3 - Design a module for Teachers CPD Programmes that supports the acquisition of these competences based on Synectics "Making the strange familiar"  instructional strategy and on the constructive alignment principle , Step 4 - Implement a 3D VCS to support the module and Step 5 - Validate the proposed module with School Teachers
Presentation of Our Module
Identify the Key Concepts
Acknowledging the 3D VWs characteristics and functionalities that could be related to education, Eshenbenner et al.  state that 3D VWs offer unique learning and teaching opportunities, as they present rich, engaging, immersive, motivating and highly interactive environments, due to the fact that they present:
Recreation of the sense of presence: The sense of presence in 3D VWs can be divided in three different types  cognitive presence, which enables students to understand and acquire the knowledge presented in 3D VWs, affective presence, which enables students to feel emotionally engaged with the educational activities presented in 3D VWs and social presence, which enables students to interact and communicate using their Avatars  in a similar way as they do in "real" life. Immediateness: The immediateness offered by 3D VWs is related to both the outcomes of the actions that the students can do in them with their Avatars and the ability to provide immediate feedback related to their interactions. Moreover, the immediateness of 3D VWs is also implemented in the tools that they present for communication and interaction allowing student to student and teacher to students real time interactions to take place . Furthermore, the immediateness offered by 3D VWs can also be used to develop systems that facilitate the exploration and the interactions with educational content and educational activities in the 3D VWs by providing students with meaningful contextual information derived from the virtual objects presented in the virtual environment . Adaptability: 3D VWs offer many opportunities to capture students' activity, develop user profiles and use this information in order to present them with personalized content according to their needs , . "Real" World Simulations: It is possible to simulate places, environments and activities in 3D VWs. Those simulations may have impact on students as they could be used either as substitutes to "real" world situations that are difficult to be recreated and/or as supplements to the "real" world allowing different types of interactions to take place in them . New Experiences: 3D VWs can be used as a means to provide students with situations that may be extremely difficult, impossible and/or dangerous to be recreated in the "real" world , giving students the opportunity to explore environments and interact with situations that may never be able to find in the "real" world . Experimentation: 3D VWs offer the possibility to support experiments that present different outcomes according to the data that students insert in them . Moreover, 3D VWs offer tools that allow the development of models of different devices for experimentation . Synchronous Communication and Collaboration: Students can collaborate and communicate in "real" time using the tools presented in 3D VWs in order to participate in educational activities that may involve the design and the development of artifacts in real time , .
Thus, these characteristics can be considered as the key concepts that would be important to be understood by school teachers who want to exploit 3D VWs in their educational practices as the affordances of 3D VWs for supporting teaching and learning. In Table Î™Î™ we present our interpretations for the representation of those concepts in the implemented 3D VCS.
Formulate a competence profile description proposal (novice level)
There is not a consistent competence description for teachers capable of effectively integrate 3D Virtual Words in their educational practices. Acknowledging this limitation and also taking into consideration the statement made by Unesco  about the effective use of technology in teaching and learning, "in order to use ICT effectively teachers must be capable of not only know how they work but also understand how to use their functionalities to support their students learning" we have devised a competence description for teachers capable of teaching in Second Life, by extending Bingell & Parson's list of skills . It should be mentioned that as there is not another similar list and/or a similar module for Teachers' Professional Development in the available literature we have started by defining the novice level of those competences in accordance to the proficiency levels (Novice, Advanced and Proficient) that were proposed as an extension to IEEE LOM in Sampson . Table I presents our proposed competence profile.
Competence Description (Novice Level)
Competences (Novice Level)
K1. Understand the key concepts of 3D VWs
K2. Understand the similarities and the differences between a 3D Virtual Classroom and a "traditional" classroom in order to identify the key concepts as "affordances" of 3D VWs for education.
K3. Understand the potential of 3D VWs to support teaching and learning
S1. Know how to use the basic functionalities of SL for navigation, control and communication according to Bignell and Parson's list (elementary and basic level) 
S2. Know how to use the tools presented in a 3D VCS
S3. Be able to transfer their own simple Educational Activities in a 3D VCS using the tools presented in it
S4. Be able to organise and present new simple Educational Activities using a 3D VCS as an environment for teaching
A1. Be interested in exploiting 3D VWs in Real Education
A2. Be motivated in participating in more Teachers' CPD programs related to the exploitation of 3D VWs in Education
Design a module for Teachers CPD Programmes
In order to design the module, we have selected to use the instructional strategy of Synectics "Making the Strange Familiar" which is defined as "a strategy for making the students understand and internalize new or difficult concepts and ideas, through the use of analogies between concepts or ideas which are familiar to the students to the new concepts or ideas presented" . Thus, based on the above we consider i) as the "strange" part of the analogy, the concepts and the competences related with teaching within 3D VWs and ii) as the "familiar" part of the analogy the teachers' experiences in a "traditional" classroom. To this end, we claim that the use of this strategy can a) facilitate teachers to understand the unfamiliar concepts presented in 3D VWs by exploring the similarities and differences between a "traditional" classroom and a 3D Virtual Classroom, and b) enable teachers to design simple educational activities by transferring their previous experiences and ideas using the tools presented in the 3D VCS.
In order to design the assessment activities of our proposed module we were based on the proposal made by  combined with the generic types of assessment activities presented in the Dialog Plus Taxonomy . The module consists of seven phases that feature different educational activities and assessment activities. In the first five phases the 3D VCS, will be used in order to demonstrate the second part of the analogy, that is, teaching in the "traditional" classroom to teaching in a 3D Virtual Classroom, whereas in the next two phases the teachers will interact within the 3D VCS exploring the analogy on their own and generating their own analogies, that is, educational activities in a "traditional" classroom to educational activities in a 3D Virtual Classroom. In Table Î™Î™ the full module is presented in a concise and consistent way.
3D VCS Implementation
Based on the educational and assessment activities we have implemented a 3D VCS that supports the proposed design following specific steps.
Step 1 - Configure Moodle Course Management System: At first we have created a Moodle Classroom, in which we have enabled specific Moodle Activities that were used to support the SLOODLE tools that are presented in the 3D VCS (namely Chat, Assignment, Glossary, Poll). Moreover, we have implemented the SLOODLE module (Version 1) along with the additional system that allows the creation of a task list and the recording of Avatars interactions within the 3D VCS, namely the SLOODLE Tracker. Step 2 - Create a Classroom Building: The main idea for the outer building was to feature transparent glasses that let the students see the outside while participating in the educational activities (as shown in picture) but also rooms that will not be visible from outsiders (e.g. classroom management room). Thus, we have used objects presenting glass, stone, steel and wood textures to create the building that features the different rooms of our 3D VCS. Step 3 - Select and Configure Supporting Tools so as to simulate the experiences presented in a "Traditional" Classroom: The main idea was to create different rooms (Table II) (Lectures Room, Lab, Library and the Assessment/Quiz Room) presenting different types of tools that can support different types of educational activities. Except for the tools the rooms were equipped with other virtual objects to make them simulate the "real world" rooms and with informative notecards that provide useful information to the teachers about the tools provided in each one of these rooms and about their functionalities. Step 4 - Provide a Classroom Management System within the 3D VCS: Considering the importance of giving teachers opportunities to transfer their own educational content and educational practices within the 3D VCS, we have created an extra room, namely Classroom Management Room. The tools and objects presented in the Classroom Management Room are the SLOODLE Tool Generator, which enables teachers create their own versions of SLOODLE tools by selecting available types of tools from a predefined list, a SLOODLE Vending Machine that stores preconfigured initialized versions of the SLOODLE tools that were used and a web interface for in-world Moodle Management. Step 5 - Present Additional Tools: The final step of the 3D VCS design and implementation was to integrate some additional functionalities that are not directly related with the educational activities but are essential for the effective organization of its assessment activities. To this end, considering the need for an Access Checker System we have integrated the SLOODLE Access Checker Door that enrolls the Avatars to the 3D VCS, maps the Avatars to their own Moodle Accounts and provides access to the 3D VCS. Moreover, in order to support the Self-Assessment on the Exploration (Skills Assessment Activity) we have integrated SLOODLE Tracker system which allows teachers' see a list of specific tasks and their descriptions but also records their interactions within the 3D VCS by setting a specific task as completed or not. Finally, to provide more scaffolding to teachers we have implemented QuizHud a system that helps the Avatars explore a place by providing them with contextual information.
3D VWs is a digital technology that bares the potential to provide benefits in teaching and learning. While its educational value is still under investigation, we can certainly claim that the key 3D VWs concepts may seem "unfamiliar" even to teachers who are experienced and keen on using digital technologies. In this paper we have presented the design and the implementation of a 3D VCS that supports a module for Teachers CPD supported that is based on "Synectics - Making the strange familiar" instructional strategy and aims to a) to support teachers understand the concepts related to 3D VWs, b) explore the new possibilities that 3D VWs present for teaching and learning and c) equip them with useful competences for teaching within 3D VWs.
The work presented in this paper has been partly supported by the Exploiting 3D Virtual Worlds in Lifelong Learning project that is funded by the Greek General Secretariat of Research and Technology.