Chalk produce, and thus widely used in the developing world, calcium-based chalk can be made where the crumbling particles are larger and thus produce less dust, and is marketed as "dustless chalk". Colored chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often colored), used to draw on sidewalks, streets, and driveways, are primarily made of gypsum. Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching of quicklime with water. In southeast England, deneholes are a notable example of ancient chalk pits. Such bell pits may also mark the sites of ancient flint mines,
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