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RPIDS and tuple issues

RPIDS and tuple issues. Henning Schulzrinne with help from Paul Kyzivat SIMPLE WG (Interim Meeting, May 2003). Open Issues. From IETF56 SIMPLE minutes: RPIDS as successor to PIDF? tuple semantics labeling elements: uniqueness across time, space, … Mailing list discussion.

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RPIDS and tuple issues

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  1. RPIDS and tuple issues Henning Schulzrinne with help from Paul Kyzivat SIMPLE WG (Interim Meeting, May 2003)

  2. Open Issues • From IETF56 SIMPLE minutes: • RPIDS as successor to PIDF? • tuple semantics • labeling elements: uniqueness across time, space, … • Mailing list discussion

  3. Step back: what do we want presence to support? • General notion of reachability for communications • Generally, device-mediated • Also, direct human-human communication (drop in and chat) • Later, maybe status (“X is travelling, so no point in waiting for her to start the meeting”)

  4. How does the system work? • RPIDS document (?) should spell out at least one scenario presence notification u1: p1,p2|p3 u2: p1,p4 u3:p5,p6 p1  u1 or u2 p1+p2  u1 p5, p5  u3 INVITE u1 Want: p1,p2,p9 caller callee

  5. Open issues – what is a tuple? • Three models have been proposed: • All share same AOR (e.g., sip:alice@example.com); selection via CP • availability of caller preferences • Custom-generated address for each capability set (maybe several for each device); e.g., sip:x45tyu7@example.com • longevity of address? • tight relationship with proxy server • Contact addresses representing devices; e.g., tel:+1-555-123-4567, sip:ph17@alice-employer.com • privacy • how long is address valid? (watcher  address book) • Not necessarily mutually exclusive – need all of them

  6. Tuple semantics • Tuple represents opaque entity, e.g., a group • easy, since few characteristics except “this is a group” • intersection or union probably makes little sense • Tuple represents media capability • “reachable by audio” • may be implemented by multiple devices • Tuple represents device (or location) • may become more important as location information increases • can be represented either by host or user part: • direct contact (sip:alice@128.59.16.1) • unique label (sip:alice+4867@columbia.edu)

  7. Tuple semantics • But really N-dimensional hypercube: • arrange by ‘category’, ‘placetype’, ‘privacy’, … • Thus, can’t hope to represent as anything but enumeration • While number of descriptors is large and will grow, number of instances represented is likely to remain smallish (~3-5?) • mobile multi-function devices make smaller number of devices seem likely

  8. Tuple perspectives • hide details of user devices (and maybe location or other aspects) • sometimes, address could be used to guess user location or behavior (aol.com  home, mobile device  traveling) • not all users will have the ability to create injective (1-1) identities • want centralized policy enforcement point for simplicity • focus on callee control • provide details • description insufficient for informed caller choice • emphasis on caller empowerment

  9. Anonymous tuples • Tuples without contact • Current meaning: face-to-face communications • Needed since presentity URI may not be usable by communications application (e.g., pres:) • May also become useful for presence focused on activity • e.g., track where rescue worker (soldier, nurse, Maytag repairman, …) is and environmental characteristics (heart rate, air temperature, …)

  10. Tuple – resolution? • Hard to anticipate uses •  document choices and trade-offs • UI considered solvable: • represent as enumeration or table (matrix) with properties in either case • use <note> to provide hints • Can’t rely on caller preferences for the near future • should we require support on caller side for disambiguation? (Opinion: policy issue)

  11. Open issues - label • PIDF defines "id" tuple tag • allows to replace changed tuples without sending all the unchanged ones • not clear from spec who modifies (PA?) and what its lifetime is • Separate "label" tag proposed • similar semantics, but set by presentity and left alone by PA • for policy filtering ("only show 'class=minimal' items when notifying low-bandwidth watchers") • Cf. Cascading Style Sheets (CSS): • "id" = unique across document • "class" = type of element

  12. Proposal: Labeling • Support class parameter/label: • similar to <div class=X></div> semantics in HTML and CSS • one-to-many: one class, many tuples • each tuple can have at most one class • inherited (if supported in RPIDS) • used for filtering and policy • Identifier (id): • for identification (replace, edit, delete) of specific tuples • unique across all tuples for presentity • should not be re-used • e.g., time of initial creation of tuple

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