content and/or documents. Roles such as editors, graphic designers, writers and producers can be explicitly modeled along with the tasks in the process and validation criteria. Commercial vendors started either to support documents or to support web content but as the Internet grew these functions merged and vendors now perform both functions. Enterprise portals—Software that aggregates information across the entire organisation or for groups such as project teams. eLearning—Software that enables organisations to create customised training and education. This can include lesson plans, monitoring progress and online classes. Planning and scheduling software—Software that automates schedule creation and maintenance. The planning aspect can integrate with project management software. Telepresence—Software that enables individuals to have virtual "face-to-face" meetings without assembling at one location. Videoconferencing is the most obvious example. Semantic technology such as ontologies—Systems that encode meaning alongside data to give machines the ability to extract and infer information. These categories overlap. Workflow, for example, is a significant aspect of a content or document management systems, most of which have tools for developing enterprise portals. Proprietary KM technology products such as Lotus Notes defined proprietary formats for email, documents, forms, etc. The Internet drove most vendors to adopt Internet formats. Open-source and freeware tools for the creation of blogs and wikis now enable capabilities that used to require expensive commercial tools. KM is driving the adoption of tools that enable organisations to work at the semantic level, as part of the Semantic Web. Some commentators have argued that after many years the Semantic Web has failed to see widespread adoption, while other commentators have argued that it has been a success. Knowledge barriers Just like knowledge transfer and knowledge sharing, the term "knowledge barriers" is not a uniformly defined term and differs in its meaning depending on the author. Knowledge barriers can be associated with high costs for both companies and individuals. Knowledge retention Knowledge retention is part of knowledge management. It helps convert tacit form of knowledge into an explicit form. It is a complex process which aims to reduce the knowledge loss in the organization. Knowledge retention is needed when expert knowledge workers leave the organization after a long career. Retaining knowledge prevents losing intellectual capital. According to DeLong(2004) knowledge retention strategies are divided into four main categories: Human resources, processes and practices Knowledge transfer practices Knowledge recovery practices Information technologies used to capture, store and share knowledge. Knowledge retention