Web 2.0 refers as the technology that provides participatory information sharing interoperability, and collaboration through the Web. A very important difference with previous technologies is that participants here have an active involvement in the formation and evolution of the web content using appropriate Web 2.0 tools and technologies. Web 2.0 tools include wikis, blogs, instant messaging, bookmarks and folksonomies, as well as podcasts and vodcasts (Saeed & Yang, 2008).

Wikis were first introduced by Ward Cunningham as a platform for exchanging knowledge between software developers (Aguiar, et al., 2009). Wikis are web-based tools that contain collections of web pages that users are allowed to edit or even create and initialize. These tools have meet a tremendous growth due to the fact that here users are not just static viewers, but they participate in this process by offering their individual knowledge about a general or a specific topic. Some other factors that contributed in the expansion of wiki-like tools include the simple wiki-syntax supported by a plethora of easy-to-use editors that simplify the process of creating and editing wiki content, as well as the fact that (in most of the cases) there is no restriction in who is allowed to change the content of a wiki page. People use wikis in collaborative projects, in collaborative writing , in course assignment, in open source software development, in organizational environments for processing and managing information, in knowledge base projects, and generally, in every online activity that requires collaborative and cooperative involvement.

Wiki is a short form for WikiWikiWeb and is derived from the Hawaiian expression “wiki wiki” meaning “fast” or “quick” (Schaffert, 2008). Ward Cunningham used the word wiki to name the collaborative tool he developed for use on the Internet in 1994. Leuf and Cunningham (2001) defined wiki as a freely expandable collection of interlinked Web pages. Another definition from O’Neill (2005) consider wikis as a collaborative medium designed to promote content sharing. Wikis allow collaborative editing of their pages as well as a full content versioning history that allow someone to roll back and find a previous version of the editing page (Ruth & Houghton, 2009). This kind of software provides an easy-to-use collaborative environment with simple and uniform navigational conventions (Grace, 2009). The Web pages created using this kind of software provide bottom up editing . The fact that the user can edit this pages using just a browser make wiki-environments the perfect tool for online synchronous and asynchronous collaboration. Wikis can also implemented to facilitate computer supported collaboration learning (CSCL), which promotes peer interaction and facilitates the sharing and distribution of knowledge and expertise among a group of learners (Augar, et al., 2004). The expertise is not in the hands of a few, but rather emerges from the combined efforts of many. The following table includes the basic characteristics of the wikis.

Nowadays, there is a plethora of available wiki tools in almost every major scripting and programming language including Java, PhP, Perl, C#, etc. Apart from the programming language that a wiki application has been built, wikis can be mainly classified according to their type including: personal wikis, semantic wikis, and structured wikis.

A personal wiki is a wiki maintained primarily for personal use where users can use this tools as a free-form database, as a personal information manager, or as a personal journal. TigerWiki is an example of a personal and minimalist open source flat file wiki application with basic functionalities such as password protection and management of page revision. Personal wikis can also transformed to multi-user wikis with personal editions. Examples of this implementation include DokuWiki and WikkaWiki. Both tools are written in PhP . However, DokuWiki works on plain text files, while WikkaWiki uses MySQL database to store pages. Bricon and Przewozny (2010) also proposed WiSe, a multiuser wiki suitable for gathering vital information produced by medical staff .

Semantic wiki is a combination of basic wiki content and Semantic Web technology (Li, et al., 2010). Semantic extension to wiki systems , based on Semantic Web technologies like Web Ontology Language (OWL) and Resource Description Framework (RDF), provide the means for further structuring and automated processing the wiki content (Witte & Gitzinger, 2007). Ontology technology can offer service about semantic query and browse, while the ontology is the obvious formalization specification of shared conceptual model (Liu & Chen, 2010). Research on ontology – based knowledge models has been largely motivated by their ability to provide unique definitions for concepts, their relationships and properties, which together create a unified description of a given domain (Malo, et al., 2010). The main idea is to make the inherent structure of a wiki, given by strong linking between pages, accessible to machines beyond more navigation by annotating existing navigational links with symbols that describes their meaning (Schaffert, 2008). Recently, many researchers are developing semantic wikis for many purposes, such as Platypus Wiki, Semantic MediaWiki, and IkeWiki(Li, et al., 2010). Platypus Wiki offers a simple user interface to create matadata based on W3C standards and suitable for implementing a personal knowledge management system. Semantic MediaWiki is an application written in PhP and the main platform in which WikiPedia resides on. IkeWiki is a Java-based semantic wiki engine that has been primarily developed as a tool for ontology engineering.

A structured wiki combines plain text wiki content with structured elements of a database. This combination makes this tool suitable for different areas like enterprise, public sector organizations, as well as for educational purposes. TWiki is a Perl based structured wiki application typically used as knowledge management system, as a team portal , etc.

Collaboration is a recursive process where two or more people or organizations work together to achieve a common goal. To be successful, collaboration requires the active engagement of the participants and the appropriate collaborative tools. Wiki based tools seems to take ground in this field, and today, more and more organizations use wiki. Wikis can be adopted in a wide range of fields and activities, from the academic environment as a tool for collaborative group assignment, or as a tool that gives the opportunity to the clients of a company to comment on company’s products and services, or as a tool that coordinates different teams in the software development process. The next sections present different areas and examples of wiki implementation.

Wiki technology has special advantages over other educational technologies, especially in its ability to allow co-editing of documents as well as the accessibility to previous versions of a produced document (Meishar, et al., 2008). Wikis can be successfully used for collaborative writing tasks among group members, as well as for creating and maintaining learning content, both by students and teachers (Popescu, 2010). According to (Kepp & Schorr, 2009), collaboration and cooperation are quite different tasks. Cooperative tasks, on the one hand, are divided into subtasks that are being accomplished separately by single group members. The contribution of wikis in this case is the communication platform that helps for a better communication among the participants and the place to host the sum of the subtasks, as well as an sophisticated environment for managing and revising the assembled work. Collaboration, on the other hand, means that the group members directly work together towards a common goal. Incremental and iterative wiki capabilities, as well as the aforementioned advantages makes this environment the perfect place for collaborative tasks (Cubric, 2008).

Wikis can be adopted in almost every educational process including online group projects, as a tool for providing online tasks such as math tasks (Martin & Premadasa, 2010), or as a self assessment system (Lui, et al., 2010). The last years more and more universities use wiki tools to provide students a platform where they can participate in group projects. The unique features of wikis such as easy editing environment, roll back capabilities, and built in search engine seems to benefit both students and teachers.

When contributing to a project, students are not just writing for the teacher, as in case of a traditional classroom environment, but for and with their peers. As such, they promote collective authoring which inherently entails peer review (Guth, 2007). Contributing to a wiki, requires students to critically read existing contribution in order to identify areas where a writer’s intended meaning is not clear or where information is lacking so as to have the possibility of changing or correcting it. Recognition of individual member’s contribution by the rest of the group has a beneficial effect on students and increase the sense of course ownership (Kennard, 2007).

On the other hand, teachers can benefit from this process because by adopting wiki philosophy students participate more actively in the project development which means less coordination efforts. Additionally, teachers can use the revision history so as to examine and analyze the progress of the project and the participation of each individual ant intervene when needed.

As it was mentioned in the introductory part of this article, wikis were first introduced as a platform for exchanging knowledge between software developers. Initially, appealed to software development organizations seeking a cost effective way to maintain up-to-date documentation. However, the flexibility of wikis support their use in other roles and software engineering activities, including project management, project communication, defect tracking, and configuration management (Aguiar, et al., 2009). Wikis are especially useful for managing distributed projects. Many developing teams around the world use them to organize, track and publish their work. Additionally, wikis have replaced the classical mailing list discussion that occurs during the software development process with a comprehensive versioning process that keeps track of every record in a history file (Louridas, 2006). The sharing knowledge that is accumulated and recorded by wikis helps managers and architects to have a better image of the software development process, and thus, to avoid past mistakes. Furthermore, this knowledge sharing mechanism can used for modeling design decisions, as well as for building patterns for future projects (Farenhorst & Vliet, 2009). Rech et al. (2007) present a wiki –platform called RikiWiki. They describe this tool as a reuse-oriented wiki with a flexible and powerful search functionality that uses case based reasoning technology and ontologies to provide a formal consistent framework for describing knowledge and experiences. The content of this tool comprises of information about products, information about projects, and information about contacts. Information about contacts concerns all the participants involved in the software development process including the stakeholders. This fact reveals that wikis provide a tool for asynchronous communication between the developing team and the stakeholders. According to Liang et al. (2009), requirements communication and negotiations is more effective when stakeholders conduct asynchronous discussion prior to the synchronous communication in a distributed requirement engineering context. The requirements elicitation process can take advantages of wikis because they provide support for open collaboration with stakeholders facilitating the collaborative exchange of ideas and information (Solis & Ali, 2010).

Globalization describes the process by which regional economies, societies, and cultures have become integrated through a global network of political ideas through communication, transportation, and trade. In this new globalized market companies face new challenges such as projects that have to be developed in more than one country or continent, or have to provide services and products around the globe. It is obvious here that traditional face-to-face contact is not always possible due to distance limitations. Wikis can cover this distance by providing capabilities for synchronous and asynchronous communication. Grace (2009) examined the adoption of wiki tools by three leading companies: Mapa, Ebay, and Ingenta. Mapa is a UK-based research company. Ebay is one of the biggest online purchasing enterprises, while Ingenta is a company that provides technology and services to the publishing and information industries. Mapa chose MediaWiki as the knowledge management system suitable for key knowledge storage as well as for recording and maintaining interaction between employees. Apart from the internal structure of the MediaWiki, one of the key factors in the adoption of this tool was the fact that most of the users were familiar with this tool due to WikiPedia. In the case of Ebay, the company was planning to adopt a tool to manage the comments and messages derived by customers. In the end, company adopted and implemented JotSpot wiki technology. The derived wiki system allow all registered members to contribute and edit eBay’s wiki content. Finally, Ingenta developed a wiki as an adequate content/knowledge sharing infrastructure for internal exchange of information.

Motivated by the expansion of wiki-like tools in almost every activity that requires online collaboration and cooperation, this article revealed the basic features of the wiki-based applications and presented some of the implementations of this software in different environments. Wikis enhance the collaboration and cooperation among the team members by providing a user-friendly environment with sophisticated capabilities for creating, structuring, classifying, and retrieving sharing information.Some of those important features that make wik a unique collaborative tool include:

• Easy syntax
• Rollback capabilities
• Embeded search engine
• Powerful page linking

As discussed earlier, some of the domains that experienced benefits from adopting wiki-base tools include:

• Education
• Software development process
• Enterprise

Wikis can be used for different purposes such as online dictionaries, as process and content management systems, as educational platforms, etc. Wikis have also helped online communities leverage a vast amount of collaboratively contributed content (Roth, et al., 2008). Famous examples include large open source software development projects such as Mozilla Firefox, Linux operating system, and encyclopedias such as WikiPedia. The last example embodies the true essence of the “Wisdom of the Crowd” (Kimmerly, et al., 2009) which is the accumulation of the individual knowledge brought together and made publicly available by democratic community of users who work unselfishly and in a voluntary basis.

Last but not least, as Web 2.0 based technologies are becoming more and more popular among young people, a very interesting aspect that should be examined and studied is in which extend have wikis been incorporated and adopted in the pedagogical process in Secondary Schools.

Aguiar, A.Dekel, U. Merson, P., 2005. Wikis4SE'2009: Wikis for Software Engineering. In: ISCE ’09 Companion Proceedings of the 2009 31st International Conference on Software Engineering. Vancouver,Canada May 2005, IEEE Computer Society, Washington, DC, USA

Augar, N. Raitman, R. Zhou, W., 2004. Teaching and Learning Online with Wikis.[Online] CiteSeerx. Available at: http://citeseerx.ist.psu.edu/ viewdoc/download? doi=10.1.1.133.1456&rep=rep1&type=pdf [Accesed 15 April 2011]

Bricon-Souf, N. Przewozny, E., 2010. How to Transform Personal Knowledge into Collaborative Knowledge with a Wiki Dedicated to Microlearning. In: 2010 Conference on Intelligent Computing and Cognitive Informatics. Kuala Lumpur, Malaisia 22-23 June 2010. IEEE Computer Society, Washington, DC,USA

Clerk, V. Vries, E. Lago, P., 2010. Using Wikis to Support Architectural Knowledge Management in Global Software Development. In: Proceedings of the 2010 ICSE Workshop on Sharing and Reusing Architectural Knowledge. Cape Town. South Africa 1-8 May 2010. ACM, New York, NY, USA

Cubric, M., 2008. Agile Learning & Teaching with Wikis: Building a Pattern. In: Proceedings of the 4th International Symposium on Wikis. Porto, Portugal 8-10 September 2008. ACM, New York, NY, USA

Farenhorst, R. Vliet, H., 2009. Understanding How to Support Architects in Sharing Knowledge. In: 2009 ICSE Workshop on Sharing and Reusing Architectural Knowledge. Vancouver, Canada 16 May 2009. IEEE Computer Society, Washington, DC, USA Grace, T., 2009. Wikis as a Knowledge Management Tool. [Online] LPIS Group. Available at: http://lpis.csd.auth.gr/mtpx/km/material/JKM-13-4b.pdf[Accessed 16 April 2011]

Guth, S., 2007. Wikis in Education: Is Public Better?. In: Proceedings of the 2007 International Symposium on Wikis. Montreal, Quebec, Canada 21-23 October 2007. ACM, New York, NY, USA

Kennard, C., 2007. Productivity and Discussion Forum Activity in a Postgraduate Online Distance Learning Course. [Online] King Soud University. Available at:http://faculty.ksu.edu.sa/74715/Documents/carl_kennard.pdf. [Accessed 15 April 2011]

Kepp, J. Schoor, H., 2009. Analyzing Collaborative Learning Activities in Wikis using Social Network Analysis. In: Proceedings of the 27th international conference extended abstracts on Human factors in computing systems. Boston, Massachusetts, USA 4-9 April 2009. ACM, New York, NY, USA

Kimmerli, J. Moskaliuk, J. Cress, U., 2009. Understanding Learning – The Wiki Way.Proceedings of the 5th International Symposium on Wikis and Open Collaboration. Orlando, Florida, USA 25-27 October 2009. ACM, New York, NY, USA

Leuf, B. Cunningham, W., 2001. The Wiki Way: Quick Collaboration on the Web. Glen View, IL, USA: Adison-Wesley Longman

Li, Y. Dong, M., Huang, R. 2010. Developing a Collaborative E-Learning based upon Semantic Wiki: From Design Models to Application Scenarios. In: 2010 10th IEEE International Conference on Advanced Learning Technologies. Sousse, Tunisia 5 July 2007. IEEE Computer Society, Washington, DC, USA

Liang, P. Avgeriou, P., 2009. Requirements Reasoning for Distributed Requirements Analysis using Semantic Wiki. In: 2009 Fourth IEEE International Conference On Global Software Engineering. Limerick, Ireland 13 July 2009. IEEE Computer Society, Washington, DC, USA

Liu, C. Chen, H., 2010. The design of E-Learning System Based on Semantic Wiki and Multi-Agent. In: 2010 Second International Workshop of Education Technology and Computer Science. Wuhan, Hubei, China 6-7 March 2010. IEEE Computer Society, Washington, DC, USA

Liu, B. Chen, H. He, W., 2008. Wiki-based Collaborative Learning: Incorporating Self-Assessment Tasks. In: Proceedings of the 4th International Symposium on Wikis. Porto, Portugal 8-10 September 2008. IEEE Computer Society, Washington, DC, USA

Louridas, P., 2006. Using Wikis in Software Development. [Online] IEEE Software. Available at: http://csdl.computer.org/dl/mags/so/2006/02/s2088.pdf [Accessed 17 April 2011]

Malo, P. et al., 2010. Semantic Content Filtering with Wikipedia and Ontologies. In: 2010 IEEE International Conference on Data Mining Workshops. Sydney, Australia 13 December 2010. IEEE Computer Society, Washington, DC, USA

Martin, P. Premadasa, K., 2010. Effective use of Wikis in College Mathematics Classes. [Online] Journal on Systemics, Cybernetics and Informatics (JSCI).Available at: http://www.iiisci.org/journal/CV$/sci/pdfs/MJ433TJ.pdf [Accessed 16 April 2011]

Meishar, H. et al., 2008. Wikis in Academic Courses: An Institutional Perspective. [Online] The Open University of Israeli. Available at: http://telem-pub.openu.ac.il/users/chais/2008/morning/2_2.pdf [Accessed 15 April 2011]

O’Neil, M., 2005. Automated use of Wikis for Collaborative lecture Notes. In: Proceedings of the 36th SIGCSE Technical Symposium on Computer Science Education. St. Luis, MO, USA. ACM, New York, NY, USA

Popescu, E., 2010. Student’ Acceptance of Web 2.0 Technologies in Higher Education : Finding from a Survey in a Romanian University. In: 2010 Workshop on Database and Experts Systems Application. Bilbao, Spain 30 August – 3 September 2010. IEEE Computer Society, Washington, DC, USA

Rech, J. Bogner, C. Haas, V., 2007. Using Wikis to Tackle Reuse in Software Projects. [Online] IEEE Software. Available at: http://csdl.computer.org/dl/mags/so/2007/06/mso2007060099.pdf [Accessed 15 April 2011]

Reinhold, S., 2006. WikiTrails: Augmenting Wiki Structure for Collaborative, Interdisciplinary Learning. In: Proceedings of the 2006 International Symposium on Wikis. Odense, Danmark 22-25 August 2006. ACM, New York, NY, USA

Roth, C. Taraborelli, D. Gilbert, Nigel., 2008. Measuring Wiki Viability: An Empirical Assessment of the social Dynamics of a Large Sample of Wikis. [Online] University of Surrey. Available at : http://epubs.surrey.ac.uk/cgi/viewcontent.cgi?article=1021&context=cress [Accessed 16 April 2011]

Ruth, A. Houghton L., 2009. The Wiki Way of Learning. Australian Journal of Educational Technology, [Online] 25(2), pp. 135-153, Available at: http://www.ascilite.org.au/ajet/ajet25/ruth.html [Accessed 15 april 2011]

Saeed, N. Yang, Y., 2008. Incorporating Blogs, Social Bookmarks, and Podcasts into Unit Teaching. In : Proceedings of the tenth Conference on Australasian Computing Education. Darlinghurst, Austalia January 2008. ACM, New York, NY, USA

Witte, R. Gitzenger, T., 2007. Connecting Wikis and Natural Languages Processing Systems. In: Proceedings of the 2007 international symposium on Wikis. Montreal, Quebec , Canada 21-23 October 2008. ACM, New York, NY, USA

Schaffert, S. 2008. IkeWiki: A Semantic Wiki for Collaborative Knowledge Management. In: WETICE '06 Proceedings of the 15th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises. Manchester, UK 26-26 June 2006. IEEE Computer Society, Washington, DC, USA

Solis, C. Ali, N., 2010. Distributed Requirements Elicitation Using A Spacial Hypertext Wiki. In: 2010 !nternational Conference of Global Software Engineering. Princeton ,New Jersey, USA 23 August – 26 August 2010. IEEE Computer Society, Washington, DC, USA