Any game or project runs on a number of assumptions that underlie the decisions made throughout its development. On the most basic level, if you've made the choice to make a Word Processor, you're probably not going to bother with joystick support; whereas if you decide to make an RPG, you're probably not going to be worrying too much about printer support.
This page attempts to provide a list of assumptions that Urban Dead runs under. For many, this will be of academic interest at best, but for those who are active in the Suggestions Section, gaining an appreciation of the assumptions underlying the game may allow you to create suggestions more likely to jive with other people's conception of the game, and more importantly will give those who are unsure of a suggestion's merit a checklist to go through.
The Pace is Slow
Urban Dead runs under a slow-pace principle - what happens in a day is artificially limited, so the pacing of action is artificially slowed. Among the reasons for this is that Urban Dead was originally conceived as a game playable in an hour each day - users could go through their turns, and log out, and come back later on - confident that the world wouldn't have changed in their off-times. And many people do play Urban Dead this way, even if you may not.
Players should always have a choice between different actions, such as choosing between firearms or melee weapons. If one of the options available to a player is much better or worse than the the other, then there is no real choice, or certainly not a very interesting one, since players will always choose the same way.
No form of attack should be superior to another
Related to the previous assumption, Urban Dead tries to ensure that whatever the means you have at your disposal, there is no clear winner. This, among other things, is why fire axes do less damage than the firearms. A fire axe needs no ammunition (you can attack day after day) whereas a firearm, while doing more damage, requires constant restocking of ammunition. A fire axe doing comparable damage to a firearm would make the firearms useless. This is also why bite and claw attacks have such disparities. The claw attack is superior in terms of raw damage, but a bite attack has many special features at its disposal.
Death is not the end
In Urban Dead, no character can be taken out of the picture for good. If a survivor dies, they can arise as a zombie. If a zombie dies, they can continue their existence as a zombie. This may seem somewhat unrealistic, but it is important from a psychological perspective - players have no desire to see months of play thrown away while they are offline.
There Ain't No Such Thing As A Free Lunch
All actions in Urban Dead incur some cost. From speaking, to moving, to attacking, to healing - all these actions require some sort of cost to be used. This is commonly Action Points, but certain actions use other forms of currency (dropping items, for instance, requires you to expend that item). It's important that any form of interaction (especially any interaction that garners Experience Points) has some cost attached to it. Certain powerful actions typically require not only an AP, but also an item.
A good question to ask is 'If something is free, what's to stop someone doing it hundreds of times? And what effect would that have on the game?' For instance, imagine an attack that's free, but only does 1 HP damage. It would be too strong, because it could be done many, many times in a single day, only stopping when the hit limit is reached, and so deal a huge amount of damage.