My character in a game wants to commission a few Iron Cobras to guard his place of residence and family against threats to them, and (ideally) intruders while they are away, without running a risk of himself and family being erroneously killed by the constructs.
The stats for the construct in question are here: http://paizo.com/PRD/monsters/ironCobra.html
Note they have no Intelligence score, speak no languages, and are not telepathic. So, how does one give a construct instructions (e.g. 'stay here and guard my family')? Is this covered by the rules, or do we have to make our own reasonable guess? Clearly because constructs are normally encountered as guards, and mythologically things like e.g. golems are controlled in part by writing, there is some mechanism (although I don't know if it is covered by the rules).
I don't believe there is a specific rule that governs the underlying commands for golems, as the crafting/set up of golems is usually handled by GMs and a healthy dose of fiat.
That said, I think your idea of it being controlled by writing is a good one, and easily applicable for this. Assuming you have approval for the crafting already, it should not be much more of a leap to get approval for this... Just ask your GM if it would be within the parameters of their world system to have your golem follow a specific set of written instructions (which it will of course follow according to the letter as written and not necessarily the intent).
The general assumption is that these 'instructions' are coded into the golem upon creation, even if the instruction is as simple as, say... 'follow CHAR and protect CHAR (and Allies, if applicable) from those who engage CHAR in combat' ... these instructions are generally implicit, but it cant hurt to have a written set if it becomes important.
Thanks. Yeah, we had discussed it and in the absence of official rules for how to set this up (which it sounds like is the case) were going to handwave something which sounded sensible based on a system like animal companion tricks. Basically "Stay in the house, don't kill my family but kill anyone who tries to."