just to expand a bit on Pertex' post:
any Value encased in double quotes is a String (literal) Value, for example (the 'alias' Attribute is a String Attribute, so, String = String: no error): player.alias = "HK"
(the 'name' Attribute is a String Attribute, so: player.name = "player", whereas, for example, player.alias = "HK". The 'name' String Attribute gives the Object, Function, Etc Element, it's ID, as can be seen. The 'name' String Attribute is the ID for quest's Elements, so quest can differentiate between the different Elements: Objects, Functions, Etc. For example, two people can have the same name, in quest, this would be the: alias, but no two people have the same ID such as their DNA, Iris-eye pattern, finger print, etc, and in quest the ID is the 'name' String Attribute)
or another example (using what would be a String Attribute and a String Value): npc1.greeting = "Hi, how are you? My name is John, what is your name?"
any Value NOT encased in double quotes is an Object (with a few exceptions that I'll tell about after --- further below), for example:
(the 'left_hand' and 'right_hand' are Object Attributes: an Attribute that holds an Object's name, and thus "pointing-getting" that Object for use, but the actual Object's location doesn't change, it's not "physically" moved to the Attribute or nor to the parent Object of that Attribute, as you can see below)
player.left_hand = shield
player.right_hand = sword
<object name="player">
<attr name="left_hand" type="object">shield</attr>
<attr name="left_hand" type="object">sword</attr>
</object>
<object name="sword">
</object>
<object name="shield">
</object>
----------------------------------------------
so, what are the exceptions?
well, at least two of them (I don't know if there's any more off-hand --- I can't think of any at the moment):
'true' and 'false', as these are reserved Values for the Boolean Attribute, for some examples:
orc.dead = false
orc.dead = true
player.flying = false
player.flying = true
player.poisoned = false
player.poisoned = true
I'm not sure if these are the correct syntax and/or terms-words for these built-in booleans (meh):
tv.switchedon = false
tv.switchedon = true
door.isopen = false
door.isopen = true
----
(so, don't name any Object as 'true' or 'false', lol --- either you'll get errors, or you'll remove-override the Boolean Attribute functionality from your game)