"Not invented here" works poorly with cloud services

This week, colleagues were discussing the "track changes" feature of Microsoft Word. They are building an automated system that uses Word at its core, and they were encountering problems with the "track changes" feature.

This problem lead me to think about system design.

Microsoft Word, while it has a COM-based engine and separate UI layer, is a single, all-in-one, solution for word processing. Every function that you need (or that Microsoft thinks you need) is included in the package.

This design has advantages. Once Word is installed, you have access to every feature. All of the features work together. A new version of Word upgrades all of the features -- none are left behind.

Yet this design is a form of "not invented here". Microsoft supplies the user interface, the spell-check engine and dictionary, the "track changes" feature, and everything else. Even when there were other solutions available, Microsoft built their own. (Or bought an existing solution and welded it into Word.)

Word's design is also closed. One cannot, for example, replace Microsoft's spell-checker with another one. Nor can one replace the "track changes" feature with your own version control system. You are stuck with the entire package.

This philosophy worked for desktop PC software. It works poorly with cloud computing.

In cloud computing, every feature in your system is a service. Instead of a monolithic program, a system is a collection of services, each providing some small amount of well-defined processing. Cloud computing needs this design to scale to larger workloads; you can add more servers for the services that see more demand.

With a system built of services, you must decide on the visibility of those services. Are they open to all? Closed to only your processes? Or do you allow a limited set of users (perhaps subscribers) to use them?

Others must make this decision too. The US Postal Service may provide services for address validation, separate and independent from mailing letters. Thus companies like UPS and FedEx may choose to use those services rather than build their own.

Some companies already do this. Twitter provides information via its API. Lots of start-ups provide information and data.

Existing companies and organizations provide data, or will do so in the future. The government agency NOAA may provide weather information. The New York Stock Exchange may provide stock prices and trade information (again, perhaps only to subscribers). Banks may provide loan payment calculations.

You can choose to build a system in the cloud with only your data and services. Or you can choose to use data and services provided by others. Both have advantages (and risks).

But the automatic reflex of "not invented here" has no place in cloud system design. Evaluate your options and weigh the benefits.