text: Q:
  
  Proper form of "user request"
  
  The context is an Internet platform to which http requests are sent. In a sentence like this:
  The system behaves differently when users' requests increase.
  
  what is the correct usage of user request terminology? 
  I have the following doubts:
  
  I think the article is not needed: is it? (when users' requests vs when the users' requests)
  Is saxon genitive mandatory, optional or must it not be used at all? I am more comfortable with user request expression but often I found the user's request expression.
  plural: are user requests and users requests both valid? If so are they interchangeable or are there some differences?
  
  A:
  
  1)  The definite article is not necessary in these kinds of contexts. In documentation of this sort, you'll see both "a user makes a request" and "the user makes a request," since you're speaking of a hypothetical user. Of course, if you defined a narrower subset of users and were speaking about them, you'd need the direct article: "Users can log in and after they've done so, the users can view their account."
  2) It's optional, and to my ear, sounds worse. I prefer "user requests," which puts the focus a little more on the request than on the user (and the system performs differently because of the requests, not because of the users). It's a subtle distinction, though.
  3) "Users requests" is not a form that you would ordinarily see, but it's grammatically valid.  Users requests would be the plural of users request. A users request would be a single request that is made by a group of users (for instance, a group of users vote on which request they want to make), or more likely, it might be a request for multiple users - i.e. not a request made by the users, but a request made by someone who wanted users.
  Remember that attributive nouns, like the adjectives they resemble, or function as, are not pluralized, unlike some other languages.
  One user request => two user requests NOT two users requests
  One mouse trap => two mouse traps NOT two mice traps
  Also note that some attributive nouns are always plural.
  One sales manager => two sales managers
  One singles bar => two singles bars
  What determines whether an attribute noun should be plural or singular?  Unfortunately, it seems there's no clear answer.  This article is insightful: "Why isn’t it a gumsballs machine?"
  
  