--- /dev/null
+++ b/lib/strokedb/nsurl.rb
@@ -0,0 +1,23 @@
+Module.module_eval do
+  
+  def self.clear_nsurls
+    @@nsurls = {}
+  end
+  def self.find_by_nsurl(url)
+    @@nsurls[url]
+  end
+  
+  def nsurl(url = nil)
+    return @nsurl unless url
+    @@nsurls ||= {}
+    mod = @@nsurls[url]
+    raise ArgumentError, "nsurl #{url.inspect} is already referenced by #{mod.inspect} module" if mod && mod != self
+    @@nsurls.delete(url)
+    @@nsurls[url] = self
+    @nsurl = url
+  end
+  
+end
+
+Module.nsurl ''
+StrokeDB.nsurl StrokeDB::STROKEDB_NSURL
\ No newline at end of file

--- /dev/null
+++ b/spec/lib/strokedb/nsurl_spec.rb
@@ -0,0 +1,60 @@
+require File.dirname(__FILE__) + '/spec_helper'
+
+describe "Some", Module do
+  
+  before(:each) do
+    @module = Module.new
+    Module.clear_nsurls
+  end
+  
+  it "should have nil nsurl by default" do
+    @module.nsurl.should be_nil
+  end
+  
+  it "should be able to change nsurl" do
+    @module.nsurl 'http://some.url'
+    @module.nsurl.should == 'http://some.url'
+  end
+  
+  it "should be findable by nsurl" do
+    @module.nsurl 'http://some.url'
+    Module.find_by_nsurl(@module.nsurl).should == @module
+  end
+  
+  it "should be able to change nsurl to the same value" do
+    @module.nsurl 'http://some.url'
+    lambda { @module.nsurl 'http://some.url' }.should_not raise_error(ArgumentError)
+  end
+
+  it "should not be able to change nsurl to the value already assigned to some module" do
+    @some_module = Module.new
+    @some_module.nsurl 'http://some.url'
+    lambda { @module.nsurl 'http://some.url' }.should raise_error(ArgumentError)
+  end
+  
+end
+
+describe Module do
+  
+  
+  before(:each) do
+    Module.clear_nsurls
+  end
+  
+  it "should have empty nsurl by default" do
+    Module.nsurl.should be_empty
+  end
+  
+end
+
+describe StrokeDB do
+  
+  before(:each) do
+    Module.clear_nsurls
+  end
+  
+  it "should have #{STROKEDB_NSURL} nsurl by default" do
+    StrokeDB.nsurl.should == STROKEDB_NSURL
+  end
+  
+end
\ No newline at end of file