what are the URLs for in claim-types

Question

Since I want to add custom claims into my application, I checked the sourcecode of ClaimTypes (decompiled with JetBrains decompiler). Here is a piece of it:

namespace System.Security.Claims
{
  /// <summary>Defines constants for the well-known claim types that can be assigned to a subject. This class cannot be inherited.</summary>
  [ComVisible(false)]
  public static class ClaimTypes
  {
    internal const string ClaimTypeNamespace = "http://schemas.microsoft.com/ws/2008/06/identity/claims";
    /// <summary>The URI for a claim that specifies the instant at which an entity was authenticated; http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationinstant.</summary>
    public const string AuthenticationInstant = "http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationinstant";
    /// <summary>The URI for a claim that specifies the method with which an entity was authenticated; http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationmethod.</summary>
    public const string AuthenticationMethod = "http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationmethod";
    /// <summary>The URI for a claim that specifies the cookie path; http://schemas.microsoft.com/ws/2008/06/identity/claims/cookiepath.</summary>
    public const string CookiePath = "http://schemas.microsoft.com/ws/2008/06/identity/claims/cookiepath";
    /// <summary>The URI for a claim that specifies the deny-only primary SID on an entity; http://schemas.microsoft.com/ws/2008/06/identity/claims/denyonlyprimarysid. A deny-only SID denies the specified entity to a securable object.</summary>
    public const string DenyOnlyPrimarySid = "http://schemas.microsoft.com/ws/2008/06/identity/claims/denyonlyprimarysid";
    /// <summary>The URI for a claim that specifies the deny-only primary group SID on an entity; http://schemas.microsoft.com/ws/2008/06/identity/claims/denyonlyprimarygroupsid. A deny-only SID denies the specified entity to a securable object.</summary>
    public const string DenyOnlyPrimaryGroupSid = "http://schemas.microsoft.com/ws/2008/06/identity/claims/denyonlyprimarygroupsid";

My question is (and I hope, it's not too silly), what are the URLs for? Are they used somewhere else? When I try to open an URL, my explorer says that the site wasn't found. So I think there is no xml-schema or something behind. If I add my custom claims, do I have to add something like those URLs too?