2.1. Why a Type System?

Imagine a scenario where a VB 6 application needs to invoke a Java application. The Java application is exposed as a Web service with one method called getData. You are writing the VB application and you are told that the Java method getData returns an integer. So you write your VB code to invoke the Web service using SOAP, which I'll cover in the next chapter. When you run your application, you can invoke the Web service, but sometimes you get runtime error 6 overflow! You get this error because a Java integer is a 32-bit number while a VB 6 integer is a 16-bit number.

What just happened was a problem due to the mismatch between the service and client type systems. To solve this problem, the client and service developer ...

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