How to create connections in sequence diagrams?
The types of connections are specified like this:

Line:
-      creates a solid line
.      creates a dotted line

Arrow:
>     creates an arrow with an open tip
/>    creates an arrow with half an open tip
>>   creates an arrow with a closed tip
>>> creates an arrow with a filled tip

Each connection has to specify a line and an arrow; e.g. "->" or ".>>>"
To create a connection in the other direction replace ">" by "<" and set it at the beginning; e.g. "</." or "<<-".
Alternatively you may swap the number of the source and destination objects.