/postgres-9.1/share/doc/html/manage-ag-overview.html
In the folowing partagrasoh 'recommendable' should be 'recommended'.
[...]
When connecting to the database server, a client must specify in its
connection request the name of the database it wants to connect to. It
is not possible to access more than one database per connection.
However, an application is not restricted in the number of connections
it opens to the same or other databases. Databases are physically
separated and access control is managed at the connection level. If one
PostgreSQL server instance is to house projects or users that should be
separate and for the most part unaware of each other, it is therefore
recommendable to put them into separate databases. If the projects or
users are interrelated and should be able to use each other's resources,
they should be put in the same database but possibly into separate
schemas. Schemas are a purely logical structure and who can access what
is managed by the privilege system. More information about managing
schemas is in Section 5.7.
[...]