Github user vasia commented on a diff in the pull request:
https://github.com/apache/flink/pull/2984#discussion_r91908249
--- Diff: docs/dev/libs/gelly/bipartite_graph.md ---
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+---
+title: Graph Generators
+nav-parent_id: graphs
+nav-pos: 6
+---
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+
+* This will be replaced by the TOC
+{:toc}
+
+Bipartite Graph
+---------------
+
+A bipartite graph (also called a two-mode graph) is a type of graph where
vertices are separated into two disjoint sets. These sets are usually called
top and bottom vertices. A single edge in this graph can only connect vertices
from opposite sets (i.e. bottom vertex to top vertex) and cannot connect to
vertices in the same set.
+
+Theses graphs have wide application in practice and can be a more natural
choice for particular domains. For example to represent authorship of
scientific papers top vertices can represent scientific papers while bottom
nodes will represent authors. Naturally a node between a top and a bottom nodes
would represent an authorship of a particular scientific paper. Another common
example for applications of bipartite graphs is a relationships between actors
and movies. In this case an edge represents that a particular actor played in a
movie.
+
+Bipartite graph are used instead of regular graphs (one-mode) for the
following practical
[reasons](http://www.complexnetworks.fr/wp-content/uploads/2011/01/socnet07.pdf):
+ * They preserve more information about a connection between vertices. For
example instead of a single link between two researchers in a graph that
represents that they authored a paper together a bipartite graph preserve the
information about what papers they authored
+ * Bipartite graph can encode the same information more compactly than
one-mode graphs
+
+
+
+Graph Representation
+--------------------
+
+A `BipartiteGraph` is represented by:
+ * `DataSet` of top nodes
+ * `DataSet` of bottom nodes
+ * `DataSet` of edges between top and bottom nodes
+
+As in the `Graph` class nodes are represented by the `Vertex` type and the
same rules applies to its types and values.
+
+The graph edges are represented by the `BipartiteEdge` type. An
`BipartiteEdge` is defined by a top ID (the ID of the top `Vertex`), a bottom
ID (the ID of the bottom `Vertex`) and an optional value. The main difference
between the `Edge` and `BipartiteEdge` is that IDs of nodes it links can be of
different types. Edges with no value have a `NullValue` value type.
--- End diff --
*A BipartiteEdge
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