>2.  Tagging: is a mechanism that consistently facilitates the formation of aggregates.  The most familiar example is a banner or flag used to rally members of an army, or the header on an internet message.
>Cas use tags to manipulate symmetries.  Because symmetries are common, we often use them in perceiving or modeling our day-to-day world.  They enable us to ignore certain details while directing our attention to others.
>Putting a stripe around a cue ball breaks the round symmetry and allows us to distinguish the previously indistinguishable.
>In general, the tag enables us to observe and act on properties previously hidden by symmetries.
>Tags are a pervasive feature of cas because they facilitate selective interaction.  They allow us to select among agents or objects that would otherwise be indistinguishable.  Well-established tag-based interactions provide a sound basis for filtering, specialization, and cooperation.
>This in turn leads to the emergence of meta-agents and organizations that persist even though their components are continuously changing. 
>Tags define the network by delimiting the critical interactions or the major connections.  The adaptive processes that modify cas select for tags that mediate useful interactions and against tags that cause malfunctions.  Agents with useful tags spread, while those with malfunctioning tags cease to exist.
>Ultimately tags are the mechanism behind hierarchical organization – the agent, meta-agent, meta-meta-agent, etc. – the organization so common to cas.