Databases Reference
In-Depth Information
“check in” to TV shows, which means they can tell other people they're
watching a show, thereby creating a timestamped data point. They can
also perform other actions such as liking or commenting on the show.
We store information in triplets of data of the form
{user, action,
item}
, where the item is a TV show (or a movie). One way to visualize
this stored data is by drawing a
bipartite graph
as shown in
Figure 6-1
.
Figure 6-1. Bipartite graph with users and items (shows) as nodes
We'll go into graphs in later chapters, but for now you should know
that the dots are called “nodes” and the lines are called “edges.” This
specific kind of graph, called a
bipartite graph
, is characterized by there
being two kinds of nodes, in this case corresponding to “users” and
“items.” All the edges go between a user and an item, specifically if the
user in question has acted in some way on the show in question. There
are never edges between different users or different shows. The graph
