To maximize component reuse, it's vital components be designed for reuse. Reusability partly depends on portability, which the Legato framework provides, but it also depends largely on interoperability. Reusable components must be designed for interoperability with as many other things as possible, including things that don't exist - yet!

Interface design is the most important factor to make something interoperable. Standardized data types and interaction methods must be used, and the simpler the interfaces, the better.

Legato embraces the philosophy that developers should always be allowed to choose the implementation language best suited to the task at hand, regardless of the components used. Some developers are better at programming in certain languages, and some languages are better suited to solving certain problems. That's why Legato provides developers with an easy way to interface components with each other, even if they have been written in different languages.

A common example of a programming-language-independent interface is a networking protocol. But networking protocols come with pitfalls and overhead, things like endian issues, race conditions, protocol stack framing overheads and poor processing time. Networking protocols also tend to require a lot of hand coding specific to the protocol implementation.

Legato supports networking, if that's what's needed, but it also has tools to implement much lighter-weight, language-independent communication between components that exist on the same host device or even running within the same process.

Function Call APIs

Virtually all programmers are familiar with function calls. While Legato allows normal libraries to use their specific programming-language function call interfaces, Legato also supports language-independent function call interfaces.

Using a simple interface definition language (IDL), you can create a function call API implemented in one language and called from another.

The implementation code (the server) can run in a different process, or even in a different application (in a different sandbox), than the client code that uses that implementation. The Legato build system automatically generates the code needed to marshall parameters and return codes into messages, and send them over the IPC system.

See Language Independent Interfaces for more information.

What's Next?

Event-driven Programming