digraph  {
node [shape=box, fontname="Helvetica Neue Light", fontsize=10];
edge [fontsize=8, fontname="Helvetica Neue Light", penwidth=.5, arrowsize=.6];

Study -> StudyCondition [label="has a set of"]
StudyCondition -> Script [label="has a set of"]
Script -> Observation [label="creates a set of"]
Reply -> Observation [label="is made in response to"]
Observation -> Email [label="can send an"]
Observation -> SMS [label="can send an"]
Observation -> Call [label="can make a"]

User -> Membership [label="participates in a study via a"]
Membership -> Study

Membership -> Observation [label="has a set of"]

Call -> Reply [label="will prompt a"]
Email -> Reply [label="will prompt a"]
SMS -> Reply [label="will prompt a"]

Call [shape=none]
SMS [shape=none]
Email [shape=none]

Observation -> Reminder [label="can have a"]
}
