Conversion of POSET to Hasse Diagram
Duration: 9 min
This video lesson is available to enrolled students.
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This educational video lecture introduces the concept of Hasse Diagrams as a graphical tool for representing Partial Order Sets (POSETs). The instructor explains that converting partial order relations into this notation simplifies their study. He defines a Hasse diagram as a drawing of the transitive reduction of a finite partially ordered set, named after mathematician Helmut Hasse. The core of the lecture focuses on a four-step algorithm to convert a relation into a Hasse diagram: drawing vertices for set elements, drawing edges for the relation, removing reflexive and transitive edges, and arranging vertices by height without direction. Two detailed examples are worked through to demonstrate the removal of redundant edges and the final vertical arrangement of the diagram.
Chapters
0:00 – 2:00 00:00-02:00
The video begins with the title slide "Conversion of POSET into a Hasse Diagram". The instructor explains that to study Partial order relations further, it is better to convert them into a more convenient notation for easier study. He introduces the "Hasse Diagram" as this graphical representation. The slide text provides a formal definition: "In order theory, a Hasse diagram is a type of mathematical diagram used to represent a finite partially ordered set, in the form of a drawing of its transitive reduction." He also notes that the diagrams are named after Helmut Hasse (1898-1979), showing a black and white photo of him on the screen. This section sets the theoretical foundation for the practical examples that follow.
2:00 – 5:00 02:00-05:00
The instructor presents a specific problem: "Consider a Partial order relation and convert it into hasse diagram?" The relation is given as $R = \{(1,1), (1,2), (1,4), (1,8), (2,2), (2,4), (2,8), (4,4), (4,8), (8,8)\}$. He lists four specific steps on the left side of the screen: 1. Draw a vertex for each element in the Set. 2. If $(a, b) \in R$ then draw an edge from $a$ to $b$. 3. Remove all Reflexive and Transitive edges. 4. Remove the direction of edges and arrange them in the increasing order of heights. He starts drawing the graph, placing vertices 1, 2, 4, and 8. He draws edges corresponding to the relation, including reflexive loops on each vertex and transitive edges like 1->4 and 1->8, creating a complex web of connections.
5:00 – 8:39 05:00-08:39
The instructor demonstrates the simplification process. He crosses out the reflexive loops (e.g., 1->1) and the transitive edges (e.g., 1->4 is removed because 1->2 and 2->4 exist). He arranges the remaining direct edges vertically: 1 at the bottom, 2 above it, 4 above that, and 8 at the top. He then introduces a second, more complex relation: $R = \{(1,1), (1,2), (1,3), (1,6), (2,2), (2,6), (3,3), (3,6), (6,6)\}$. He draws vertices 1, 2, 3, 6. He draws edges 1->2, 1->3, 1->6, 2->6, 3->6. He removes the reflexive loops and the transitive edge 1->6. The final Hasse diagram is arranged with 1 at the bottom, 2 and 3 in the middle layer, and 6 at the top, forming a diamond shape. He removes the arrowheads to complete the diagram.
The lecture effectively bridges the gap between abstract set theory and visual representation. By defining the Hasse diagram as a transitive reduction, the instructor clarifies why certain edges are removed. The step-by-step algorithm provided (draw vertices, draw edges, remove reflexive/transitive, arrange by height) serves as a reliable method for students. The two examples illustrate different structures: a simple chain (1-2-4-8) and a diamond lattice (1-2/3-6), showing how the method adapts to different partial orders. The final diagrams clearly show the hierarchy of the sets without the clutter of redundant information.