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Subject: RE: [xdi] New versions of 3 key XDI docs posted


Using the terminal notation how would you encode the XDI statement saying that the inlined icon for ="" is
Or using terminals would you just not encode any binaries into XRIs?  If so this would cause some problems, and I think XDI should be able to support binary data. 

Alternatively there could be a method that works with terminal notation for specifying the encoding of the literal (or language for strings), something like !($mime/image/gif) with the literal value being the binary data.

Also, how is the use of ! as denoting a persistent identifier distinguished versus ! as data predicate?
Kind regards,
Bill Barnhill
Booz Allen Hamilton - Belcamp,MD

From: xdi@lists.oasis-open.org [xdi@lists.oasis-open.org] on behalf of Drummond Reed [drummond.reed@xdi.org]
Sent: Wednesday, February 08, 2012 9:50 PM
Subject: [xdi] New versions of 3 key XDI docs posted

XDI TC Members and Observers,

I just uploaded new native and PDF versions of the three key docs we've been using to document the evolution of the XDI graph model towards our 1.0 specification suite. Please review these before the call if you can so we can dive right into the main topics of the call.

Below is the set of public links (as always, all of these are also consolidated on a single page on the XDI TC wiki: http://wiki.oasis-open.org/xdi/XdiGraphModel):

XDI GRAPH MODEL - 21 page Word doc explaining the core model

XDI GRAPH PATTERNS - 14 page Powerpoint doc with examples of all basic patterns

XDI STATEMENTS FOR XDI GRAPH PATTERNS - 8 page Word doc with XDI statement sets corresponding to each of the example graphs in the above. STRONGLY RECOMMENDED TO READ IN PARALLEL WITH  XDI GRAPH PATTERNS.

A summary of the key changes in these new versions:

  1. They show the use of literal contexts - modeling an RDF literal as an XDI context with a single literal arc represented by the XRI "!" and the XDI object node containing the literal value. (See detail below.)
  2. They show the use of nested root contexts - root nodes (open circles) below the current root node that identify other local XDI graphs. (See detail below.)
  3. They show the use of root contracts - the "bootstrap" link contract needed off an XDI root node to establish root-level permissions for an XDI local graph (and show the network origin of an XDI message).
  4. The ordinal context pattern (using *1, *2, etc. as contexts to explicitly order XDI graph nodes) is now more explicitly defined and illustrated.
  5. In the XDI Graph Patterns doc, more example graphs have been added, and more explanation for each graph, to make it easier for newcomers to understand the different patterns and how they fit together.

The advantages of the literal context proposal:

  1. It gives every literal in the XDI graph its own XDI address without using a cross-reference - simplifying navigation and XRI processing time.
  2. It makes it much cleaner to express and navigate XDI metadata, such as datestamps and versioning.
  3. It simplifies parsing and serialization, since all semantics describing a literal will be in the XDI subject identifying it, and every XDI literal (now called a "terminal") will have an XDI predicate consisting only of "!". (Note that Victor Grey has suggested another XRI delimiter character could also be used for this - he suggests ":").

The advantages of the nested root contexts proposal:

  1. It provides a clean way to model the relationship of different local XDI graphs available at different XDI network endpoints for the purposes of XDI discovery.
  2. It shows how a single physical XDI server (such as an LDAP server, SQL database, NOSQL database, etc.) can implement a "multi-tenant" model where it can host multiple independent local XDI graphs yet still have them logically appear as part of the global XDI graph.

I will put these proposals on the agenda for tomorrow's telecon.


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