Because of the ever changing nature of work and society under knowledge-based economy in the 21st century, students and teachers need to develop ways of dealing with complex issues and thorny problems that require new kinds of knowledge that they have not ever learned or taught (Drucker, 1999). Therefore, they need to work and collaborate with others. They also need to be able to learn new things from a variety of resources and people, and to investigate questions and bring their learning back to their dynamic life communities. There have arisen in recent years learning community approach (Bielaczyc & Collins, 1999; Bereiter, 2002) and learning ecology (Siemens, 2003) or information ecology approach (Capurro, 2003) to education. These approaches fit well with the growing emphasis on lifelong, life-wide learning and knowledge building works.
Following this trend, the Internet technologies have been translated into a number of strategies for teaching and learning (Jonassen, Howland, Moore & Marra, 2003) with supportive development of one-to-one (e.g. e-mail posts), one-to-many (such as e-Publications) and many-to-many communications (like video-conferencing). The technologies of Computer-mediated communications (CMC) make online instructions possible and have the potential to bring enormous changes to student learning experience of the real world (Rose & Winterfeldt, 1998), as individual members of learning communities or ecologies help synthesise learning products via deep information processing processes, mutual negotiation of working strategies and deep engagement in critical thinking, accompanied by an ownership of team works in those communities or ecologies (Dillen-bourg, 1999). In short, technology in communities is essentially a means of communication-based creating fluidity between knowledge segments and connecting people in learning communities. However, this online collaborative learning culture is neither currently emphasised in local schools nor explicitly stated out in intended school curriculum guidelines of formal educational systems in most societies.
Emergence of a new learning paradigm through CMC
Through a big advance in computer-mediated technology (CMT), there have been several paradigm shifts in web-based learning tools (Adelsberger, Collis & Pawlowski, 2002). The first shift moves from content-oriented model (information containers) to model (communication facilitators) and the second shift then elevates from communication-based model to knowledge-construction model (creation support). In knowledge- construction model, students in web-based discussion forum mutually criticise each other; hypothesise pre-theoretical constructs through empirical data confirmation or falsification, and with scaffolding supports, co-construct new knowledge beyond their existing epistemological boundaries under the social constructivism paradigm (Hung, 2001). Noteworthy, only can the third model can nourish learning community or ecology, advocated by some cognitive scientists in education like Collins & Bielaczyc (1997) and Scardamalia & Bereiter (2002). Similarly, a web-based learning ecology contains intrinsic features of a collection of overlapping communities of mutual interests, cross-pollinating with each other, constantly evolving and largely self-organising members (Brown, Collins & Duguid,1999) in the knowledge-construction model.
Scaffolding supports in social constructivism and web-based applications
According to Vygotsky, the history of the society in which a child is reared and the child's personal history are crucial determinants of the way in which that individual will think. In this process of cognitive development, language is a crucial tool for determining how the child will learn to think, because advanced modes of thought are transmitted to the child by means of words (Sch