The Basics - Reverse Engineering a Database
(Page 8 of 8 )
Reverse engineering is, as the name suggests, the reverse of forward engineering or code generation from a UML model. So, reverse engineering is when you create a UML model from an existing VS .NET project or even from an existing database. With VSEA, you do any reverse engineering from within the VS .NET IDE. With stand-alone Visio 2000 Professional and Enterprise Editions, Visio 2002 Professional Edition, and the Visio 2003 Professional Edition, you can do it from within Visio.
As an example, let’s try reverse engineering a database table. We’ll reverse engineer the Customers table from the Microsoft Access Northwind example database,7 but you can just as easily choose to reverse engineer a copy of the Customers table from your own organization. In Exercise 1-16, make sure you replace the Microsoft Access Northwind bits with the setup for your desired data source.
EXERCISE 1-16
- Open VEA (if it isn’t already open).
- To create a new database model, select File -> New -> Database -> Database Model Diagram.
- Start the reverse engineering by selecting Database -> Reverse Engineer. This brings up the Reverse Engineer Wizard, as shown in Figure 1-22.
Figure 1-22. The Reverse Engineer Wizard
4. If you already have an ODBC DSN for the data source you want
to reverse engineer a table from, select it from the Data
Sources list and skip to step 13. If not, click the New button to
create one. The Create New Data Source dialog box is now
shown.
5. Select the System Data Source option and click Next.8
6. Select Microsoft Access Driver from the list and click Next.
7. Click Finish. The ODBC Microsoft Access Setup dialog box is now
shown.
8. Type Northwind in the Data Source Name text box.
9. Click the Select button. This brings up the Select Database
dialog box, which is really nothing more than the well-known
Open File dialog box.
10. Browse to the Northwind.mdb database file on your system, or
type in the name and path in the Database Name text box. It’s
usually located in the Program Files\Microsoft Office\Office11
\Samples folder (if you have Microsoft Office 2000 or Microsoft
Office XP installed).
11. Click OK.
12. Click OK in the ODBC Microsoft Access Setup dialog box.
13. Click Next.
14. Click OK in the Connect Data Source dialog box, unless you
have specified a user name or a password for the database.
15. Remove the selection from the Views option on the database
objects review page of the Reverse Engineer dialog box and click
Next.
16. Select the Customers table on the database tables review page,
as shown in Figure 1-23.
Figure 1-23. The database tables review page of the Reverse Engineer Wizard
17. Click Finish. Your database model diagram is now updated with
the reverse-engineered Customers table, as shown in Figure 1-24.
Figure 1-24. The reverse-engineered Customers table on a class diagram
Summary This chapter introduced you to enterprise modeling by means of one UML model that was used for generating a class (Logon) in VB .NET and C#, as well as a database model that was used for generating a small database with just one table (User) in Microsoft Access.
These two simple models were described in detail, and you saw how the two models were created and how the actual code and database were generated from within VEA. You also saw how you can reverse engineer an existing database into a database model diagram.
So why would you really want to use modeling for your enterprise solutions? Well, modeling is quick, and it saves a lot of the drudgery of repeated typing because of DDL scripts and the code skeleton generation. Modeling also serves as part of the solution documentation. Another important reason is that you reduce the risk of errors when data names and data types are transcribed between designs, databases, and application code.
The next chapter presents some guidelines for how to design and plan your projects and solutions.
1. A UML model is never really complete, meaning you can always find
things that can be expressed in a more detailed way. Our intention
in stating that a model can be complete or incomplete is that you
can say it’s complete when all parties involved are satisfied that
the information they want is contained in the model in the desired
details. In other words, when it’s good enough to proceed to the
next stage.
2. Rational Software was acquired by IBM, and the company is now
called IBM
3. If you have specified that VS .NET should open the last loaded
solution when opening, you can change that from the Options
dialog box, or you can manually open the generated code file.
4. The next version of VS .NET, code-named Whidbey, should be able
to handle unsigned data types. It is scheduled to be released
sometime in 2004.
5.
Table is a physical database term, and entity is a conceptual
database term. You should keep this in mind, because Visio
sometimes seems to mix the two.6. You can just as easily choose one of the other options, but for the
sake of this example, please follow the exercise.
7. The Northwind sample database comes with most versions of
Microsoft Access, but it’s also an optional setup part of Microsoft
SQL Server 2000.
8. You can just as easily choose one of the other options, but for the
sake of this example, please follow the exercise.
 This article is excerpted from Enterprise Development with Visual Studio .NET, UML, and MSF by John Erik Hansen and Carsten Thomsen (Apress, 2004; ISBN 1590590422). Check it out at your favorite bookstore today. Buy this book now. |
| DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware. |
