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Subject: XDI TC Unofficial Telecon Notes: Monday 2016-04-11

XDI TC Notes

Following are the notes of the unofficial telecon of the XDI TC held on:

Date: Monday, 11 April 2016 USA
Time: 10:00AM - 11:30AM Pacific Time (17:00-18:30 UTC)

The TC operates under a standing rule approved 17 July 2008 under which the TC does not hold regular official meetings and conducts all business by electronic ballot only. Unofficial weekly meetings are held to enable discussion among members but no business is conducted nor actions taken.


Markus Sabadello
Drummond Reed
Les Chasen


Phil Windley
Markus Sabadello

XDI Bindings to Connectionless Protocols

Recent discussions about blockchain-based identity registries have reopened the subject of defining XDI bindings to connectionless protocols. One suggestion has been RAET (Reliable Asynchronous Event Transport):


Drummond explained that while RAET is not yet in wide use, it is gaining interest for distributed ledgers, which from an XDI standpoint are an attractive technology for root identity registries.

Joseph pointed out the similarity to MQTT. Drummond quoted this passage from the page linked above:

Modern large scale distributed application architectures, wherein components are distributed across the internet on multiple hosts and multiple CPU cores, are often based on a messaging or event bus that allows the various distributed components to communicate asynchronously with each other. Typically the messaging bus is some form of messaging queue service such as AMQP or ZeroMQ. The message bus supports what is commonly referred to as a publish/subscribe methodology for information exchange.

And also this passage:

Because UDP/IP has lower latency and is connectionless, it is much better suited to many small asynchronous messages and scales better. The drawback of bare UDP/IP is that it is not reliable. What is needed, therefore, is a tuned transport protocol that adds reliability to UDP/IP without sacrificing latency and scalability. A transactioned protocol, is much more appropriate for providing reliablity to asynchronous event transport than a streaming protocol.

Drummond said that so far, all the implementations are in Python, and payload of the protocol is a Python dictionary, so it should be able to serve as a transport protocol for XDI messages.

Joseph pointed out that from an XDI messaging standpoint, the key is how it works with any connectionless, asynchronous protocol in general, not so much any one specific connectionless transport. The issues such as acknowledgements and message order should be similar no matter what the connectionless protocol is, and should be specified in the XDI Messaging spec.

Les agreed, and suggested that we need to test it out in implementations like XDI2.

Semantic Filtering

In our last call about group messaging, Drummond agreed to do a separate writeup on semantic filtering to show that it is an orthogonal topic. He has posted it to this wiki page:


Drummond reviewed the concepts of channels and threads as laid out in this wiki page. Joseph then asked about the potential for conflicting link contracts within a single group. The example he used is if the group has a policy saying only members of the group can access all the messages, but a group admin adds a link contract allowing people outside the group to access a specific thread.

This boils down to a conflict between the terms of two link contracts. Drummond said this is likely to be one of the hardest areas of link contracts and policy _expression_ to get right. The best place to solve that problem is restricting the ability for a group admin to add a link contract that would violate existing group policy.

Drummond believes that semantic filtering as expressed by “channels” and threads should be covered in XDI Messaging 1.0. We’ll take that up further with Markus on the next call.

Internet Identity Workshop - April 26-28


Drummond and Les are planning to attend. Joseph said he is not sure if he’ll be able to attend. As always, we hope to have multiple XDI sessions there as needed.


The next call will be the following week at the usual time (Monday 10AM PT). The link to where agenda items can be posted for the next meeting is: https://docs.google.com/document/d/19oDl0lbb56Grehx2a5flZnhrgnua5l8cVvC_dJ8fTXk/edit?usp=sharing

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