Creation of N-TIER MODEL (and use of webservices)

Hello,


I've build an N-Tier Model and would like to know if I'm going the right way... (it's the first time I'm building such model)


My N-Tier Model actually looks like this :

Windows Forms
     |    
Windows User Controls
     |
Business Workflow
     |
Business Logic
     |
Data Factory
     |
Data Access
     |
Common Class



Explanation :
---------------


Content of the following layers :

Windows Forms (exe): only forms (user interface);
                                 The windows forms layer has access to the Win User Controls, Business Workflow and Common class.

Windows User Controls (dll) : own and external usercontrols or dlls;
                                           The windows User controls layer has access to the Business Workflow and Common class.

Business Workflow (dll): workflow of 'business logic'-functions;
                                   The business workflow layer has access to the business logic and  Common class.

Business Logic (dll): functions like : build tree, fill grid, calculate, ...;
                             The business logic layer has access to the data factory and common class.

Data Factory (dll): functions that will execute queries to the database. (ex. fill user information, get list of customers,...);
                           The data factory layer has access to the data acces and common class.

Data Access (dll): functions : create connection with database, destruct connection, execute queries with or without results;
                          The data access layer has access to the common class.

Common class : global functions : write to log, format sql queries, format datetime,... .
                        The common class layer has access to nothing.



I also want to use webservices. Do I've to use 1 or several webservices? Which layer will be located in which webservice?


Maybe I only have to use 2 webservices :

Webservice 1 contains :
     * the business workflow layer;
     * the business logic layer;
     * the common class layer.

Webservice 2 contains :
     * the data factory layer;
     * the data access layer.


Thanks a lot for your help !