The Knowledge Building (KB) theory was created and developed by Carl Bereiter and Marlene Scardamalia for describing what a community of learners needs to accomplish in order to create knowledge. The theory addresses the need to educate people for the knowledge age society, in which knowledge and innovation are pervasive.
Scardamalia & Bereiter distinguish between Knowledge building and learning. They see learning as an internal, (almost) unobservable process that results in changes of beliefs, attitudes, or skills. By contrast, Knowledge building is seen as creating or modifying public knowledge. KB produces knowledge that lives ‘in the world’, and is available to be worked on and used by other people.
The best way to understand the difference between learning and knowledge building is by considering Mathematics and Scientific contents as examples of public knowledge. Furthermore, Bereiter in his book on Education and Mind (2002) based his observation of the educational value of Knowledge Building on Carl Popper's Ontological analysis of our existence as made up of three interacting worlds: World 1 (the physical), World 2 (the subjective) and World 3 (the locus of cultural products). Thus, learning takes place in World 2, while knowledge is built in World 3. 
Knowledge building refers to the process of creating new cognitive artifacts as a result of common goals, group discussions, and synthesis of ideas. These pursuits should advance the current understanding of individuals within a group, at a level beyond their initial knowledge level, and should be directed towards advancing the understanding of what is known about that topic or idea. The theory "encompasses the foundational learning, subskills, and socio-cognitive dynamics pursued in other approaches, along with the additional benefit of movement along the trajectory to mature education".
Knowledge building can be considered as deep constructivism  that involves making a collective inquiry into a specific topic, and coming to a deeper understanding through interactive questioning, dialogue, and continuing improvement of ideas. Ideas are thus the medium of operation in KB environments. The teacher becomes a guide, rather than a director, and allows students to take over a significant portion of the responsibility for their own learning, including planning, execution, and evaluation.
One of the hallmarks of Knowledge building is a sense of we superseding the sense of I, a feeling that the group is operating collectively, and not just as an assemblage of individuals. A wide variety of discussion software can enable such an environment, one being Knowledge Forum, which supports many of the prerequisite processes of Knowledge building. Bereiter and colleagues  state that Knowledge building projects focus on understanding rather than on accomplishing tasks, and on collaboration rather than on controversy.
Knowledge building may be defined simply as "the creation, testing, and improvement of conceptual artifacts. It is not confined to education but applies to creative knowledge work of all kinds".
Setting children on a Knowledge building trajectory is a promising foundation for education in the knowledge age (Scardamalia & Bereiter, 2003).
In her 2002 article on Collective Cognitive Responsibility for the Advancement of Knowledge, Scardamalia proposes 12 principles of Knowledge building.MT
Principles of Knowledge building
Scardamalia (2002) identifies twelve principles of Knowledge building as follows:
- Real ideas and authentic problems. In the classroom as a Knowledge building community, learners are concerned with understanding, based on their real problems in the real world.
- Improvable ideas. Students' ideas are regarded as improvable objects.
- Idea diversity. In the classroom, the diversity of ideas raised by students is necessary.
- Rise above. Through a sustained improvement of ideas and understanding, students create higher level concepts.
- Epistemic agency. Students themselves find their way in order to advance.
- Community knowledge, collective responsibility. Students' contribution to improving their collective knowledge in the classroom is the primary purpose of the Knowledge building classroom.
- Democratizing knowledge. All individuals are invited to contribute to the knowledge advancement in the classroom.
- Symmetric knowledge advancement. A goal for Knowledge building communities is to have individuals and organizations actively working to provide a reciprocal advance of their knowledge.
- Pervasive Knowledge building. Students contribute to collective Knowledge building.
- Constructive uses of authoritative sources. All members, including the teacher, sustain inquiry as a natural approach to support their understanding.
- Knowledge building discourse. Students are engaged in discourse to share with each other, and to improve the knowledge advancement in the classroom.
- Concurrent, embedded, and transformative assessment. Students take a global view of their understanding, then decide how to approach their assessments. They create and engage in assessments in a variety of ways.
- Educational psychology
- Progressive Inquiry
- Knowledge environment
- Knowledge Forum
- Fle3 - Future Learning Environment
- Knowledge building communities
- Constructionist learning
- (Scardamalia & Bereiter, 2003)
- (Popper, 1996)
- (Scardamalia & Bereiter, 2003, p. 5)
- (Scardamalia, 2002)
- (Scardamalia, 2002)
- (1997, p. 12)
- (Bereiter & Scardamalia, 2003, p. 13)
- Scardamalia (2002)
- Bereiter, C. (1994). "Implication of Postmodernism for Science Education: A Critique." In: Educational Psychologist Vol. 29, n. 1, pp. 3–12.
- Bereiter, C. (2002). Education and Mind in the Knowledge Age. Mahwah, NJ: Lawrence Erlbaum.
- Bereiter, C., & Scardamalia, M. (1993). Surpassing Ourselves: An Inquiry into the Nature and Implications of Expertise. Chicago, IL: Open Court.
- Bereiter, C., & Scardamalia, M. (2003). "Learning to Work Creatively with Knowledge" In: E. De Corte, L. Verschaffel, N. Entwistle, & J. van Merriënboer (eds.), Unravelling Basic Components and Dimensions of Powerful Learning Environments. EARLI Advances in Learning and Instruction Series.
- Bereiter, C., Scardamalia, M., Cassells, C., & Hewitt, J. (1997). " Postmodernism, Knowledge Building, and Elementary Science". In: Elementary School Journal. Vol. 97, n. 4, pp. 329–340.
- Popper, K. (1996). Knowledge and the Body-Mind Problem – In defence of interaction. (Edited by M. A. Notturno) London and New York: Routledge.
- Oshima, J. (2005). Progressive Refinement of a CSCL-Based Lesson Plan for Improving Student Learning as Knowledge Building in the Period for the Integrated Study. Proceedings of the 2005 Conference on Computer Support for Collaborative Learning.
- Scardamalia, M. (2002). "Collective Cognitive Responsibility for the Advancement of Knowledge". In: B. Smith (ed.), Liberal Education in a Knowledge Society. Chicago: Open Court, pp. 67–98
- Scardamalia, M., & Bereiter, C. (2003). "Knowledge Building". In: J. W. Guthrie (Ed.), Encyclopedia of Education. 2nd edition. New York: Macmillan Reference, USA. Retrieved from
- Scardamalia, M. (2004). Ask the experts: what's the next revolution in education going to be? [Video series]. Ontario Institute for Studies in Education, University of Toronto. Link to video
- Zhang, J., Scardamalia, M., Reeve, R., & Messina, R. (2009). Designs for collective cognitive responsibility in knowledge building communities. Journal of the Learning Sciences, 18(1), 7–44.pdf
- Fle3 Learning Environment - Fle3 is an open source online tool for knowledge building