Software Identification Tag is required ?

InstallShield is itself a bad idea anyway. Please see my comment below to see what I mean...
—SA

Using InstallShield is a pretty bad idea. I would advise using open-source WiX. Compared to WiX correctly using Microsoft standards, InstallShield looks plain "illegal" (not legitimate, in terms of the standardized project schema, please see my comment below).
—SA

I have InstallShield and I LOVE it. I don't see anything wrong with the legality of it.

"Legality" is just a figure of speech. I'll explain what's wrong. Microsoft created standard MSBuild with API (you can develop your own "Tasks" using .NET, for example) and standard XML-based schema for all projects. If you look at .NET and some other projects of different types, you will see that they follow the same schema, which is standardized. This way, you can created your own project types, buildable in a standard way. WiX follows this standard. Therefore, you can use, say, target Platform (in fact, this is the target instruction-set architecture, feature especially important for setup, because MSIs for different architectures are incompatible, but you want to build them from a single source) in a standard way, the same way as other BSBuild-standardized properties. So, WiX is really legitimate and perfectly integrated. Even the Setup project template supplied with Visual Studio is not following the standard; that's why Microsoft deprecated it for new Visual Studio version. And, at this time, I don't know anything correctly following the project standard except WiX, which also has very good Visual Studio integration (Intellisense, in particular). Another option is creating a custom setup project directly based on Windows Installer API (fully available with SDK), but this is quite inappropriate for most installations...
—SA