Possibilities

The user can:

Representation of a labeled transition system

A labeled transition system is a labeled directed graph.

Nodes

Source node and destination node are represented by numbers. The current state maintained by the system is a reference to a source node. A node can be marked as explored or unexplored. Unexplored nodes are called leaves and transitions whose destination nodes are leaves are called leaf edges. A node is explored after clicking upon a transition coming in it or after clicking upon the last action button.

Edges

The edges will be classified in levels, which are identified by the length of the shortest path from the initial state to the source node of the edge. The edges are devided into two sequences which are both stored in stacks ordered by level number and source number.
edges of the spanning tree
they connect parents (source nodes) with their children (destination nodes). Each node can have left or right neighbours which are nodes having the same parent. The left neighbours are earlier generated than the current node and the right neighbous are later generated.
cross edges
they connect parents (source nodes) with any already reachable node.
A stack frame consists of edges of the same level.

Restrictions

Not all edges which are generated will be kept in memory during the entire run. If a state is explored all departing transitions are added to one level above the current level and all transitions in the levels higher than that level will be popped from the stack(s). This is possible because transitions are levelwise stacked in memory. The transitions in one above the current level will become leaf transitions, which implies that the destination nodes of them will fall back into the status of unexplored.