When Do You Use Web Services?
Let's say that your company uses a supply-chain application that stores your customers' orders in a SQL Server database and keeps track of each order's status. Currently, when customers want to know which of their orders are pending, they contact your customer-service representative, who queries the database for that information. Customers then update their ordering systems. But suppose a customer wants to streamline the process by using an application to request order status directly from your system. To enable this type of access to your system, you and the customer need to agree on the interface the customer will use to make the request and the format in which you will return the requested data.
This scenario is an ideal application for Web services because you can use SOAP to build a single standards-based interface that works for many different customers with varying needs, regardless of the software applications and computing platform their enterprises use. Additionally, SOAP lets you build a loosely coupled interface that incorporates XML as the data format. (A loosely coupled application lets you reconfigure, redeploy, or relocate the implementation without affecting dependent applications.) By using XML, you gain extensibility that lets you expand the scope of the data you can provide to your customers in the future. Simply put, supplying a Web service lets you leverage the full value of XML's standard format, extensibility, and platform independence.
—Rich Rollman, Exploring XML
"Web Services in Action," July 2002 InstantDoc ID 24910
Ending Errors
Use error handling in your applications to prevent errors such as reaching the end or beginning of the recordset. You can use the EOF or BOF properties of the recordset to detect this error. For example, to check for the end of recordset when the user clicks the button, you can change the cmdNext_Click event to the following code:
If Not envNorthWind.rsCustomers.EOF]
Then envNorthWind.rsCustomers.MoveNext
End If
For a better approach, you can detect the end or beginning of the recordset and disable any navigation controls so that users can't click them. This method provides better feedback than letting the users click the button, then find out that they're at the end of the recordset.
—Ken Spencer, VB Toolkit, "Jump Start Your Database Project"
March 1999, InstantDoc ID 4886