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Data Sharing With Alice And Bob

Revision as of 16:24, 17 December 2010 by (Talk | contribs) (Share Alice's (Alice and Bob) with Bob)



This document describes a use case wherein Alice offers to enter into a data sharing relationship with Bob.

A cursory knowledge of the concept of a Attribute Data Service 2.0 and of the Persona Data Model 2.0 (PDM 2.0) is assumed. Although not mentioned explicitly the graph of objects being shared are described in the PDM 2.0 model.

This use case assumes that there is an active client providing a little bit of UI and the ability to kick off sending an email to Bob. But the reality is that 95% of the implementation of this use case is done by the PDS Client 2.0, so a webapp (built on the PDS client library/service) could just as easily have provided the UI instead of an active client with its so-called dashboard UI. Best of all if both kinds of clients existed they would of course interoperate seamlessly.


Alice wishes to delegate to her friend Bob authority over the record in Alice's Google Contacts (think gmail) account that is about him, to him. In inviting Bob to do this she simultaneously offers him read-only access to the record about herself.

The social protocol is that Alice sends an offer to "stay in sync" to Bob. The offer contains two gifts: (i) a link to the record about Alice so Bob can always have her latest information and (ii) a link to Bob's record so that anytime Bob's information changes Alice gains a copy.

Initial Condition

Alice has:

  • A Higgins-based active client
  • A PDS that supports "sharable" contexts (e.g. exposing them via a UDI of some kind)
  • A gmail account wherein at least her friend Bob is listed.
  • A PDS provisioned with a Google Contacts Context Provider (CP). This CP syncs with the Google Contacts API and exposes a Higgins PDM 2.0 compatible context.

Bob has:

  • No active client
  • No PDS
  • No gmail account

Alice Opens Her Google Contacts

As shown below, Alice opens a Google Contacts context, providing her gmail username/password credentials. If Alice does not have an entry for herself in Google, then an empty one is created. If Alice does have an entry for herself this is somehow found.[1]

Alice 2.0.106 1 .png

A note about the images in this document. The round cornered boxes are Higgins contexts. The dotted lines are foaf:knows attributes. The solid lines are h:correlation links--which very roughly means "this is another facet of me"


Since no h:correlation link exists between Alice's root entity in the root context and the root node in the Google Contacts (GC) context, then this correlation is added. We then walk the graph from the root node in the Google Contacts context and copying/merging each p:Person node into either a new/existing context under the root (aka RootMe) node.

The result of this generalization process is shown below. The dotted lines are foaf:knows links. For clarity all of Alice's contacts (other than herself and Bob) have been omitted from Figure 2 below.

Alice 2.0.106 2.png

Share Alice's (Alice and Bob) with Bob

In the UI of the active client Alice selects the "Bob" p:Person node. One of the operations she can perform on this node is to share it with someone. She chooses to share this p:Person node with Bob. And by Bob we mean here Bob's email address (which is an attribute of the Bob node). For social protocol reasons Alice will simultaneously offer to share her own contact info with Bob. (See the "Stay in Sync?" email below).

The PDS Client 2.0 needs to add Bob to the access control list for the contexts. Since at this point we only know Bob as his email address, so that must (for now) be his identifier. The access control list is maintained by the PDS, so Alice's PDS Client must communicate with the PDS to add Bob to the "allow access" list of the alice context and the bob context. We add "Bob has full read/write access" to the bob context's ACL. And we add "Bob has read-only access" to the alice's context ACL.

The last step is for the active client to arrange that an email be sent to Bob. The email contains what we call an i-link.

The i-link (URI) encodes (a) a link to an active client download site (b) the UDI of the Bob entity (c) the UDI of the Alice entity on r-card1

The text of the email says something like:

Subject: Stay in sync?
I'd like to stay in sync with you. By clicking on the link below please accept my offer to always having my latest contact/profile information. You have the option of Click here to accept my offer. Note: If you don't already have a Higgins active client, clicking here will bring you to a download page where you can get one. I've started using Higgins to stay in sync with co-workers, friends and family. With Higgins everything stays up-to-date because everyone who uses Higgins only has to update their own contact info--and all the changes are automatically reflected it everyone else's address book.

Bob clicks on the i-link

Since Bob's browser doesn't have the Higgins BX installed when he clicks on the i-link it just takes him to the Higgins download site. Bob downloads and installs an active client. Now Bob has a root context as shown in Figure 4 below.

Alice 2.0.106 3.png

Bob processes the i-link

Bob extracts the UDI of Alice's Bob entity on r-card2 as well as the UDI of Alice's Alice entity on r-card1.

Alice not only delegates control over her representation of Bob to Bob but also the data management of this representation.

The result would be:

Alice 2.0.106 4.png

Note: If Bob also had a gmail (or interestingly any other kind of context!) account of his own that contained nodes for himself and/or Alice he could later open this context and push a "Correlate" button on the PDS Client to compare graphs and infer/suggest new h:correlation links.
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