In Context

March 21, 2010

Apps and Personal Data Stores

This post presents an architecture comprised of apps, a dashboard, and a personal data store (PDS) that can be implemented by multiple developers, hosted by multiple operators over an open, personal data network and whose goal is to give users more control over their own identity (personal data, profiles, preferences, affiliations, and relationships). It is in support of aspirations that have been widely reported by others and called variously VRM, data portability, user-centric identity, the Data Web, Augmented Social Network (2003), and so on.

I’ve annotated the diagram above with little “H” and “A” markers so you can see specifically the areas that Higgins and Azigo are working on respectively. Lots of other folks are also working on other parts of the picture too, of course.


Apps are of course the most important kind of component since they are what the end user sees and appreciates. Apps gain access to the user’s data by making calls (e.g. getAttribute) to an API exposed by the PDS Client. Architecturally, we’ve seen the need to support both conventional kinds of apps: web, mobile (iPhone, Android, etc.), and desktop, as well as a more unusual kind of app, I’ll call a Javascript app.  In this latter case Javascript is fetched from a web service (e.g. from Kynetx KNS) injected locally into your browser by a browser extension. This same browser extension exposes the same PDS Client API to this Javascript program.


The dashboard is an admin GUI app for your personal data. It is an occasional-use tool that provides: (a) a control panel to manage the permissioning policies that control which of your attributes are shared with whom (including so-called “selector” functionality to approve the release of your info)  (b) a dashboard GUI to see and manage all of your identity data attributes (including profile data, credentials, friends lists, etc.) whether stored in your own PDS or managed by others (c) a place to directly enter self-asserted attributes (d) an embedded app marketplace (e) a canvas area where apps can extend the UI to add their own admin interfaces (f) a place to import & manage your i-cards and OpenID OP relationships.

ASIDE: Dashboard is a new word I’m trying out. The reality is that this piece of software is a bit of a swiss army knife where each blade/tool is called something different. A few examples: Microsoft calls the aspect that pops up to give notice and consent to release a set of attributes an identity selector. Inside Google they call identity-related client add-ons to a browser an active client. The “show me all of my stuff” aspect does sound like a dashboard. On the other hand, the permissioning aspect is something Eve would call a relationship manager (or I think she would). And I think Bob Blakley would too.

The dashboard combines aspects of earlier client efforts. In 2006-2007 we saw Information Card Selectors like Windows CardSpace as well as the Higgins selectors provide an interface to view and manage multiple digital identities displayed as visual cards, as well as provide notice and consent to the release of your selected digital identity. In 2009 Azigo augmented the selector concept support for Kynetx apps in Azigo (along with cross-platform and card roaming support). Prototypes shown by Microsoft (e.g. OpenID Active Client) and Higgins at IIW in 2009 added OpenID support thus demonstrating multi-protocol support. Mozilla Lab’s Account Manager is doing some great work in this area. The Higgins project is working on a next-generation client as part of the Higgins 2.0 Active Client expected in 2011.

Personal Data Store

A PDS is a web service that works on your behalf, giving you more control over your own personal data whether it is stored in the PDS or managed elsewhere. PDS stores local attributes in blinded form so that only the user has the decryption key–not the PDS service provider. The PDS is an idea that has been underdevelopment for years. For some background see Joe Andrieu, Joe again, and Iain Henderson. As part of Higgins 2.0 the PDS is being developed. Another interesting PDS development project is Mine!

PDS Client

The PDS Client has no UI, but provides an API for apps that wish to read/write attributes from the PDS. Here are some of its functions:

  • Maintains (and syncs to the PDS and other clients) the user’s ”permissions”–the decisions that the user has make as to who (what app or relying party) has access to what attributes. For example, the first time a new app/RP asks for a certain set of attributes, the PDS Client will trigger the PDS Dashboard to present the policy decision to the user. The next time this same request happens, the PDS Client remembers the grant and usually doesn’t have to bother the user about it this time.
  • Maintains a local copy of some or all of the person’s personal data stored in the remote PDS
  • Maintains an OAuth WRAP access token that it gets by authenticating itself to an external authentication service. It passes this token along in XDI messages to the remote PDS service.
  • Can be configured to encrypt attribute values before they are sent over the wire (e.g. in XDI messages) to the remote PDS
  • Contains a local Security Token Service (STS) that allows it to create and sign SAML (for example) tokens for self-asserted attributes.
  • Contains an STS client to support remote IdP/STSes managed by external parties (e.g. to support managed i-cards).
  • Performs cross-context schema mapping.

The Higgins 2.0 PDS Client is packaged as either a C++ or Java code library or as a separate operating system process (e.g. on Windows it is a Windows Service).

Network Protocol

Drummond Reed with his OASIS XDI and OASIS XRI work was first to my knowledge to define an open data web. A few years later Tim published his Linked Data paper. We’re starting to see implementations of Linked Data so now the Semweb folks also have a data web. Both of these approaches are important.

An open community is starting to form around the XDI that is focused on PDS-related use cases and create might be called a profile of XDI in this area. The community is leveraging XDI’s existing strengths in the areas of identity management integration, security, access control, data sharing and versioning, as well as extending them where needed in order to meet the PDS-related requirements.

This focus probably provides a critical time-to-adoption advantage over the Linked Data effort in this PDS area. Since the objective is interoperability (i.e. an interoperable ecosystem of PDSes and apps over a common protocol) assembling a community focused on this area would seem to be the fasted way to get there. Linked Data (like “vanilla” XDI) has a much broader link-all-the-worlds-data-together mission and lacks direct support for many of the PDS-related requirements. As a consequence RDF developers (including Higgins) define ad-hoc extensions to RDF to make it support the PDS use cases that are only interoperable within their own developer community.

PDS Schema

The Higgins PDS uses its own internal schema called the Persona data model. This is not to say that the PDS architecture imposes a single ontology on its clients. Quite the opposite. Every attribute call (e.g. getAttribute) may request attributes in any vocabulary. As I’ve mentioned in my schema mapping post, we follow the philosophy of mapping into and out from the internal schema.

Authorization Manager (AM)

The AM provides the “back end” authorization manager for access control of attributes managed by data services other than your own PDS. The Higgins project has been tracking the promising UMA Authorization Manager effort that Eve Maler and others have been developing.

Kynetx KNS

KNS is a web service that serves up compiled Javascript apps for injection into browsers. The app developer uses the Kynetx AppBuilder tool to create apps. Each app is packaged as an information card. The developer puts this app on their website for folks to download and install. If you click on it and already have a PDS Dashboard the new app gets installed in about one second. If you click on it an you don’t already have a PDS Dashboard, then you download an installation package that includes a Dashboard (with the app pre-installed inside it).


  1. [...] Paul Trevithick’s blog about identity and social networks – latest entry Name [...]

    Pingback by The Semantic Web & THE POWER OF PULL » Blog Archive » Identitywoman and the New Identity Platform — April 12, 2010 @ 8:48 am

  2. [...] initiatives like the Open Action Network and Personal Data Stores are taking the first steps towards bridging the gap between our digital lives and our actions in [...]

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  3. Any way the best is to pub. an open data, for example see open personal page (only for older than 18 years old!)- and no problem of store.


    Comment by Seve — October 31, 2011 @ 3:13 pm

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