Just some short-hand notes (not complete thinking) to capture thoughts-in-progress:
Presence & identity: At the core, presence is "you" but how many "you"'s are there? I have many personas: Principal Analyst at Burton Group, a technology geek to my circle of friends, father/husband to my family, a customer to some companies I deal with, etc. In some cases, I'm a made-up person (screen names on AOL or a member of some social networking site). It's important to not go too far down the road in terms of solving presence without due diligence regarding how it relates to identity and how identity is managed and secured.
Presence & location: Presence also touches upon where I am - my home office, on the road at a Starbucks, at a hotel, at a conference, etc. Location information is also important to consider when devising a strategy around presence.
Presence & environment: Somewhat related to location, presence could include insight to the environment around you - the capabilities and/or constraints of your computing environment (connectivity not good enough for video) as well as the form factor(s) you have at the moment (mobile device vs. a PC).
Presence & activity: Presence is influenced/impacted by the activity you are involved in as well as the activities of others. Certain activities preclude me from being available. Other activities might make me freely available. And there are all sorts of combinations in-between.
Presence & role: People wear many hats. There are default roles that might show up in a presence profile but perhaps not all possible permutations. There might be roles that are viewable through certain filters. For instance, someone might be considered a first responder in case of an emergency on their floor in a corporate office. Loading the filter for a "first responder role" into a presence system could display that view of presence information. Roles might also be tacit, my activities might grant me a role for some duration, or my expertise (know-how) or network strength (know-who) might make me "present" on-the-fly.
Presence & meta data: Presence can be assigned to artifacts. I might tag an artifact with meta-data that is resolved in real-time (e.g., author for a document, subject-matter expert) that might only display in a list of search results. Presence is attachable to any application element. Presence as "live" meta data (presence-enabled systems) is a good discussion to have with developers (workflow, etc).
Presence & availability: Availability is a subjective thing - always, sometimes, never, to everyone, to someone, to no one. If I say no one do I not mean my wife or boss. Can I delegate availability? How does availability relate intelligently to all the above (when I am in a certain activity I am unavailable)?
Presence & Social Relatedness: Presence conveys a type of peripheral vision and social nearness (cognitively) that it is important to consider the "connectedness" implications of presence in terms of social networks and community.
Presence & attention: Both inward attention (managing access, interruptions) as well as outward attention (am I trying to get noticed, or to let someone know something, by setting my presence status to a certain state).
Presence & federation: Not just across various organizational boundaries but also across identity boundaries. Security (confidentiality, privacy) comes into play more prominently.
Presence of objects: presence of "things" as well as people so RFID is a type of presence. My presence can be inferred from objects near me or that I handle or wear (nTag).
Presence & agents/avatars: As technology progresses and we automate tasks via bots of various sorts, what type of presence do these "instances of me" have as they act as my proxy? Am I present in real-life when I am in Second Life?
I'll end with that one ... food for thought and for consideration as to how some of these items relate to assumptions currently made around presence systems. How many assumptions based on instant messaging, IP telephony and so on will get in the way of a more expansive view of presence? How do we deal with the discovering, aggregating, brokering, filtering, de-duping, syndicating and other issues? Are we wrong to assume only SIP-based presence systems need apply? Will we have a flat presence server model (federation, clearinghouses) or will we also need a server-of-server model? There's a lot to consider, from many angles - socially, organizationally (including business process and application aspects) as well as technically.
I've covered real-time collaboration since 1996 and for the past few years (at Meta and at Burton) have argued that presence needs to be considered as its own architectural topic.