Containers and Contributors

 

To allow for a variable number of parameters for a tag, the concept of containers and contributors is supported within VTS. A "container" is a tag that holds a collection of other tags known as "contributors". A tag may be a container for multiple contributor types, and a tag may also contribute to several different containers. A tag may also be a contributor and a container at the same time (a container tag may accept values from its contributors, while in turn contributing its value to another container). For example, each station in a given area might contribute its value to a container that calculates the value for that area, and each area container might contribute its value to a container that calculates the value for the province or region. These regional containers can also contribute their values to a container that calculates a national value.

The container uses a "handle" variable that lists the contributors for a given tag. There may be several handle variables defined, one for each kind of contributor possible. There is no naming restriction on handle variables, but both the contributor and container modules must know the name. A handle variable is exclusively manipulated by three VTS functions:

•      AddContributor

•      DeleteContributor

•      GetContributors

These functions are outlined in the sections that follow.