This paper describes the solution of the tasks of visualizing the graphs of the internal representation of Cloud Sisal programs, visualizing the process of computing and debugging Cloud Sisal programs. The formal definitions of the graph with ports and the graph model with ports and attributes are shown. A model of the visualization of the graph model with ports and attributes is described using static images in the SVG format. A model of displaying changes in the graph model with ports and attributes using animations supported by the SVG vector graphics format is described. The connection of graphic animations displaying changes in visual styles and changes in the attributes of the graph model with ports is implemented using Petri nets. It describes the modeling of calculations corresponding to the functions of a given Cloud Sisal program using the hierarchical Petri nets, where the transitions correspond to the functions, and the places of arguments and the parameters of the corresponding functions. Also described modifications of hierarchical Petri nets, ensuring the functionality of the breakpoints and editing the arguments or the results of functions at activated breakpoints for debugging purposes by adding additional places and transitions. Thus, for the obtained Petri nets, the possibility of changing markup of places in the process of functioning is considered.