What are some good educational systems for preschool?

What is a good open-source system for personal knowledge management systems?

• I'm looking for recommendations or pointers to projects. Many companies, included, host privately-sourced knowledge, in a symbiotic relationship with content providers.  However, a silo is still a silo, no matter how convenient, and once you get in, it's hard to get out.  Who knows what will become of users' intellectual property in the long run?  Related questions: Compared to , I'm looking for a stronger focus on conceptual-level data modeling, and some extensibility of the core models, and good support for prototyping and development of http://en.wikipedia.org/wiki/Personal_knowledge_base systems. What open source software meets (or is aimed at) the following  requirements, and would support innovation, "social", and longevity? Strong on concept modeling with extensible data models and database Ability to "federate" with similar systems into clusters Reasonable scalability to content and to size of clusters Suitable base for personal knowledge-based systems Bi-directional connectors for private social media and curation platforms such as Quora, ScoopIt, FaceBook, LinkedIn, Twitter (etc.) ...along with the generic capabilities such as Signon (User ID), API, etc. Some systems are partway there.  Some are partly open, with a free level or version, but not open source. - Open, but not open-source. and - http://en.wikipedia.org/wiki/Locker_%28software%29

• Answer:

  Have you tried http://libertreeproject.org/ yet ? It is open-source, but I'm not sure if it fits all your requirements.