Conditions and Tolerances are used in Skelebrator to define the scope of Skelebrator operations. They consist of an attribute (e.g., diameter), an operator (e.g., less than) and a unitized value (e.g., 6 inches). These values together define the effect of the condition. The examples just listed when combined into a condition would reduce the scope of an operation to only skeletonizing pipes with a diameter less than 6 inches.

A condition is able to be assessed based on a single element type, regardless of topology. It is possible to assess whether pipes meet the specified condition of diameter less than 6 inches without knowing the pipes’ location in the hydraulic model. Tolerances, however, are different. They are assessed based on the ensuing topology, and thus, the meaning of a tolerance varies depending on Skelebrator operation type. Additionally, the tolerance operator is not available when it doesn’t make sense. For example, it does not make sense to define a pipe tolerance for Smart Pipe Removal since only a single pipe is being considered at a time. An example of a valid tolerance is for Branch Collapsing where a junction tolerance can be specified between the two end junctions of the pipe.

Conditions and tolerances are cumulative. That is with every additional condition, the number of pipes able to be skeletonized will be reduced. Setting conflicting conditions such as diameter < 6-in. and diameter > 8-in. will result in no pipes being able to be skeletonized since conditions are joined with the logical AND operator. It is not possible to specify OR conditions or tolerances.

It is possible to specify no conditions for a particular operation. In that case all pipes are valid for skeletonization based on their physical attributes.

However, conditions and tolerances are not the only elements that determine whether a pipe will be skeletonized. For a pipe to be skeletonized it has to meet all of the following criteria:

• Be valid in terms of the network topology with respect to the particular skeletonization operation. That is, during Branch Reduction the pipe has to be part of a branch. Any pipes whose topology dictates they are not part of a branch will not be skeletonized.
• Must not be an element that is inactive as part of a topological alternative. All inactive topological elements are immune to skeletonization.
• Must not be referenced by a logical control, simple control, or calibration observed data set.
• Must not be connected to a VSP control node or the trace node for WQ analysis.
• Must not be a user-protected element.
• Must meet all user defined conditional and tolerance criteria.