Indexing with servo motors

Servo motor manuals have numerous pages with electric data, tables and diagrams. There are so many data which are useless for the design engineer. How are we going to select the correct servo motor for an indexing application?
One solution is to ask an automation engineer and describe him exactly the specifications of our application. Personally, I always want to learn and exercise my ability to select the appropriate components and purchased parts for the given application (increasing my experience) so I prefer to ask the right questions for future use.
The first data we need to know is the torque vs rotation speed (servo performance curves).  Usually two curves are given, one for the peak and another for the continuous operation. From these performance curves we can choose accordingly to the application torque needs.

Secondly, we must know the number of points per revolution (ppr) of the encoder (or resolver) of the servo motor. The servo motors simple divide their revolution in many steps, tracking each one of them and stop their move exactly in each one of them. Knowing the number of points per revolution is critical. The reason for this is the number of indexing steps that our application must perform. This number must divide exactly the number of points per revolution of the servo. For example if we have to create an application with 8 indexing steps we must select a servo motor with 1000 ppr (1000 divided by 8 equals 125) or 2000 ppr (2000 divided by 8 equals 250) and so on. In the other case where the steps are not exact numbers, the servo will perform the indexing cycle and will stop at the nearest point. This will create an accumulate error of the servo rotation which must be resolved after a few cycles (resolved by servo programming). This kind of operation creates a non smooth rotation and at the correction cycle we observe a correction movement of the equipment (usually a forward jump). The third thing we must know is about our servo motor type, if it is equipped with an encoder or with a resolver. The encoder or resolver type defines the durability of our servo motor against shock loads.