Ask HN: Is it a CMS I am looking for?

I am trying find some form of a content management system not geared towards the publishing of web pages, but rather that of custom content. I am sure there is a name for these kinds of systems/applications, but I cannot come to think of it.

My basic requirements:

1) There needs to be a way to create templates for objects in a flexible manor, where a template is a set of attributes, with the ability to create nested groups of attributes as well as add attributes associated with other templates

2) Content instantiates these templates

3) Arbitrary sets of content needs to be exportable, preferably to custom XML

4) All this needs to be accessible through a decent management UI, web-based preferably. Ideally there is an API somewhere in there as well

What am I looking for? I feel that traditional CMS:es are too tied to that of web publishing. I guess I am looking for something a bit more generic.