Posture consists of forward, upward and rightward directions.
Each directions has 2 degrees of freedom, but the set of them has only 3 degrees.

Recall that the posture can be represented as a unit quaternion.
The unit quaternion has a constraint on its length, so thus it has 3 degrees of freedom.

In these days, I am thinking about how web services can be provided without shutting down.
An answer I got is keep it small.
Small services can be provided without maintenances.
For example, the Formula (http://formula.s21g.com/) has been provided for more than a year. But it had virtually neither maintenances nor updates.
But it is used by someone sometimes.

The cost of keeping such services is about $50 a month.
It consists of only the cost of an EC2 instance.
An instance can offer several such services, so the cost would be shared by them.
So thus the individual cost becomes more low.

Suppose the cost is $20 a month,
we can gain it by a fund of $4800 if it earns 5% a year constantly.
If it is possible, it can be a new way for providing services such as the Formula.