Last year Andreas Weigend taught Stats 252 at Stanford and shared the following list of opposing characteristics of data communication:

Structured Unstructured
Symmetric Asymmetric
Relevance Chronological
Synchronous Asynchronous
Searchable Not Searchable
Private Public
Broad Narrow
One-time Ongoing
Spontaneous Planned
Short-term Identity Persistent Identity
Push Pull

It’s always interesting to see the different startup companies focusing on different aspects of data.

There’s more to this list, so make a comment and add to this list.