Chalk It is formed in the sea by sub-microscopic plankton, which fall to the sea floor and are then consolidated and compressed during diagenesis into chalk rock. Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacture now may utilize mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum (calcium sulfate). While gypsum-based blackboard chalk is the lowest cost to
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