According to Hugh MacLeod a social object:

is the reason two people are talking to each other, as opposed to talking to somebody else.

also:

social networks are built around social objects, not vice versa. The latter act as “nodes”. The nodes appear before the network does.

In discussions around architecture there can often be much confused talk around what is needed, what an architecture looks like and what decisions need to be made in order to make it so. There are three useful architectural social objects that help cystalise our thoughts and  allow a network of related artefacts to be created. These are:

• Use Cases or Scenarios – Illustrate what I am trying to do via real-world examples that use human actors to illustrate what we are trying to achieve.
• Architecture Overview – The main architectural elements (components) that the system is comprised of.
• Architecture Decisions – What decisions am I making, what options did I consider and why did I choose the ones I did.

These social objects seem to apply to all levels of architecture from the smallest application to the largest enterprise architecture. Of course they are by no means all you need but serve as a pretty good starting point for all that follows.