Conceptual Content

The concept hierarchy can be synthesized from a careful blend of existing taxonomies. For an initial proof of concept, two useful taxonomies are from sign language and the food pyramid. Use of sign language extends all the way to toddlers, as an increasingly popular supplemental communication before they develop speech abilities, such as the "Sign With Your Baby" materials. 100 basic signs provide some of the most useful concepts for basic living: http://www.lifeprint.com/asl101/pages-layout/concepts.htm . Sign language may be doubly useful in some cases, when motor skills allow for communication with the manual signs. Icon libraries are already established for American Sign Language, and readily available for many of the USDA food pyramid categories: http://openclipart.org/media/tags/vegetable .
Optimal open icons for development: http://imaginesymbols.com