For a graph G = (V, E) and a nonempty set X, a linear hypergraph set-indexer (LHSI) is a function f : V(G) → 2X satisfying the following conditions: (i) f is injective (ii) the ordered pair Hf(G) = (X, f(V)), where f(V) = {f(v) : v ∈ V(G)}, is a linear hypergraph (iii) the induced function f⊕ : E → 2X defined by f⊕(uv) = f(u) ⊕ f(v), for all uv ∈ E is injective and (iv) Hf⊕(G) = (X, f⊕(E)), where f⊕(E) = {f⊕(e) : e ∈ E}, is a linear hypergraph. It is shown that a 3-uniform LHSI of a graph, corresponding to upper LHSI number, is unique up to isomorphism and possible relations between the coloring numbers of a given graph and the two linear set-indexing hypergraphs are established. Also, we show that the two hypergraphs associated with an extremal 3-uniform LHSI of a graph are 2-colorable and the corresponding induced edge hypergraphs are self-dual.