The format of the ACTIVECHILD operator is:
A typical use:
The operator allows for activity when excitation is received on one of the hierarchy operators:
In operation, a new value flowing into one of these operators will cause a search for an ACTIVECHILD operator. As an example,
TimePeriod has attributes StartDate, FinishDate and Duration. Each of these has attributes of a numeric value (together with other attributes). If the numeric value is pushed into the FinishDate ATTRIBUTES operator, say, then the head of that operator is searched for an ACTIVECHILD, and its parents. Searching will move along a chain, so the first ATTRIBUTES led to its head, and its head will be checked if it is the child of another ATTRIBUTES operator. If so, searching will start on the head of that operator, and its parents.
If an ACTIVECHILD operator is found, the appropriate diffuse operator matching its name is called, together with the chain of variables and operators that led to it. The diffuse operator assembles the information, evaluates it and propagates it. That is, the diffuse operator is nowhere and everywhere.
See Diffuse Operators