Skeleton is a visual scripting environment as an extension of Squeak etoy [1] with Connectors [2] system to make mathematical and physical simulation for non professional computer user. Squeak etoy system is a unique attempt to provide effective way of programming for children in learning environment. Skeleton makes logical relationships among graphical objects in the etoy system with spreadsheets-style interface, and users can describe object?s behavior in declarative representation.

Concreteness is one of the key words of end user scripting. Direct manipulation with objects on the screen is helpful to understand what is happened in your computer. Skeleton?s spreadsheets style interface realizes this concreteness to show any input and output data same time.

Sometime user scripting system like etoy has a problem of modularity. This aspect is important as a basis of reusing, thus Skeleton has some features for reusing. Tree structured naming system like ECMAScipt [3] is used to access to Skeleton object by name. And modularity is realized by sheet-card mechanism that is possible to reuse a behavior of objects in another context in Skeleton.