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Section 19.3 Graph for a partial order

Hasse diagram
a diagram for the graph for a partial order on a finite set \(A \text{,}\) omitting reflexive loops and transitive “composite” edges, and placing “smaller” elements lower on the diagram instead of using arrows

Example 19.3.1. Hasse diagram for division of integers.

Let \(A = \{2,4,6,8,10,12\} \text{.}\) The Hasse diagram of the “divides” partial order \(\mathord{\mid} \) on \(A \) appears in Figure 19.3.2. Notice that \(2 \) is not joined directly to either \(8 \) or \(12 \text{,}\) since we can use transitivity and the facts that \(2 \mid 4 \) and \(2 \mid 6 \) to infer \(2 \mid 8 \) and \(2 \mid 12 \text{,}\) respectively, from the diagram.
Hasse diagram for the “divides” partial order.
Figure 19.3.2. The Hasse diagram for the “divides” partial order on a finite set of integers.

Example 19.3.4. Hasse diagram for subset order.

The graph from Example 14.4.1 has been reproduced in Figure 19.3.5 as a Hasse diagram, and represents the partial order \(\mathord{\subseteq} \) on \(\powset{\{a,b,c\}} \text{.}\)
Hasse diagram for the subset partial order.
Figure 19.3.5. The Hasse diagram for the subset partial order on the power set of a finite set.