Initially there had only been the standard single target mechanism for all procedures. Later on people started to develop more sophisticated ways of deliver a payload. However there is still only a rather small different number of mechanisms. Namely the following 6:
As mentioned the straight forward way. One target and that's it.
Now who would have guessed. Here one can aim at 2 things. Both targets can be identical however for maximal on point effect.
Same as double just with 3 targets. Again an attack can be focused on only 1 target. One can also hit 1 target once and a second one twice.
The strongest of the multiple target procedures. It can do anything from targeting 4 enemies to targeting one enemy 4 times in a row. Very effective and very expensive.
All the above have in common that a target can evade being targeted by its visibility value. However if aimed at ones own library the visibility value will be threatened as if it would be 200%. So aiding procedures got a very high chance of success on your own, but are much harder to do on friendly units. You can toast your own library with an attack procedure using that 200% bonus as well however. But who would do that???
This is a completely different way of attacking. Instead of focusing on a target, an area procedure rather aims at a whole area around the library. That way it does not need a target line. It will also hit all and everything in the battleground. Great if fighting more then 1 enemy. However unfortunately it will also affect your own library.
On the bright side at least the 200% bonus does not apply here. So the executing library got the same protection against the procedure as the others. On first glance an area procedure might seem stupid, however if one fights 3 or more enemy tasks it is very useful. Another idea would be to run an evade procedure on ones own library to lessen the chance it is hit first.
More or less the same stuff again. Other does the same Area damage effect. However an Other procedure is designed to memorize its point of origin. So it does not share the self-harm problem of the Area procedures. That memorising is rather processor intensive stuff however to make sure it is not fooled. As a result Other procedures are even more expensive then Quadruple ones.
Additionally to the six basic target mechanisms there are two target modifiers. Each procedure can have one target mechanism and up to two target modifiers. These two are:
A guided procedure is designed to circumvent the enemy's visibility ratio. It will always hit as if the enemy would have a visibility of 200%
Often libraries are so heavily shielded an attack is almost useless. Now one can either Soften them up or take a penetrating procedure. These goodies are designed to go right through the defences as if they would be 0%.