Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
Blackboard (design pattern) component; it generally takes the form of a complex scheduler that makes use of a set of domain-specific heuristics to rate the relevance of executable knowledge sources. Usage-domains include: The blackboard pattern provides effective solutions for designing and implementing complex systems where heterogeneous modules have to be dynamically combined to solve a problem. This provides non-functional properties such as: The blackboard pattern allows multiple processes to work closer together on separate threads, polling and reacting when necessary. An example of the Blackboard pattern has been provided by Microsoft. https://social.technet.microsoft.com/wiki/contents/articles/13461.blackboard-design-pattern-a-practical-example-radar-defense-system.aspx Blackboard (design pattern) In software engineering, the blackboard pattern is a