Fred Riggs, who is known as the Father of Comparative Public Administration is propounder of ecological approach. He wrote the book “The Ecology of Public Administration” in 1962 in which he threw light on the relationship & interaction of an administration with its external surroundings. He analyzed that many factors like political, social, economic, administrative etc. are influenced by its environment & in turn influences the environment in which it works.

In his approach, he described two types of models-
[A] Agraria-Transita-Industria Model [1956-1957]
[B] Fused-Prismatic-Diffracted Model [1959] [Outcome of ATI MODEL]
Fused-Prismatic-Diffracted Model deals with underdeveloped, developing & developed societies. For this he used the example from Thailand [Underdeveloped Society] & contemporary U.S.A [i.e. developed society].
Between both of these extremes, there exists the PRISMATIC SOCIETY which has administrative sub-system known as “SALA” Model.

Riggs mainly focussed on Prismatic Society & its features by a diagram of PRISM.

Fused society performs multiple functions i.e. there is a large volume of work whereas in diffracted society there are specific & limited no. of functions,
There are 3 basic features of Prismatic-Sala Models:-
1. HETEROGENEITY:– In this type of system, there are different kinds of patterns, rules, systems & viewpoints. This society is a blend of elements of “CHAMBER” [i.e. of fused society] & “BUREAU”
[i.e. of diffracted society]. Thus heterogeneous group where the qualities are not alike are seen in this Model.
2. FORMALISM:- This is the second most important feature which show a wide gap between theory & practice i.e. what is formally prescribed & effectively practiced. It shows a distinction between norms & realities.
3. OVERLAPPING:– This features shows that differentiated structures [clubs] co-exist with undifferentiated structures [Sects]. This denotes overlapping of administrative behavior of both the societies.
Riggs called these elements as “CLECTS”(club+sects).

Besides this many other features are also presented like polynormativism, polyfunctionalism, polycommunalism, bazaar-canteen model, authority v/s control, price indeterminacy, political instability, etc. To conclude, Riggs gave his new theory entitled in a book-”Prismatic society-Revisited” in 1973.

For this he gave Bi-dimensional
[i] Differentiation [ii] Integration.
These elements are necessary to be presented in a Prismatic society developing towards Diffracted society.