Informatics (worse: Computing science; even worse: Computer science) is the discipline of automated data processing (where automation is both human independent and dependent, and data in context becomes information). The non-IT industry has learned the hard way over the last few decades that informatics is part of their core business, not just some support function. Financial institutions, automotive suppliers, advertising agencies and so forth are all recognizing that informatics is a key business aspect for them.
In academia, informatics, once it became its own department, needed a home. The usual politics ensued, with informatics becoming a part of the engineering faculty, the natural sciences, or (rarely) the humanities, all depending on the university and who held the best cards. There was no particular rhyme or reason, just politics. With the recognition of the fundamental importance of informatics for pretty much every human undertaking today, this isn’t good enough any longer.
At first, one might think that informatics is in a similar position to mathematics. It has to serve many different masters, supplying other disciplines with teaching services and basic education.
However, informatics is also much more than that. Unlike mathematics, informatics changes all these disciplines. Informatics advances the concepts and methods of other disciplines, but more importantly, informatics changes the research objects of these disciplines. This is most obvious in the humanities: The innovations of informatics are changing society and individuals. It is somewhat obvious in medicine and engineering: The innovations of informatics are providing new models and technologies that let us see the world in a new light and change it accordingly. It is perhaps least obvious in the natural sciences, but the innovations of informatics help create new explanatory models in biology, chemistry, and physics to the extent that some believe it is informatics all the way.
Rather than jockey about “owning” informatics, the department of informatics is probably best viewed as its own independent faculty with far reaching interconnections to about every other department in the other faculties. Short of that, I’d still put informatics into engineering, but that’s probably because I’m a software engineering researcher and educator.