Post on 27-Jan-2015
description
XMPP, TV and the Semantic WebOr ‘how I got to work on something that wasn’t entirely about RDF for a change…’
Dan Brickley – VU WAI talk, Feb 1st 2010
“This will be a very informal and very short talk to introduce The XMPP (Jabber) internet protocol and some potential impact
it has for TV and Semantic Web applications."
Extensible Messaging and Presence Protocol (XMPP)
• Open standard for Instant Messaging (IM) chat• Alternative to vendor-specific closed networks• Built opensource-style, then ratified at IETF• How it works:– userid@my.example.com ‘JIDs’– Neverending 2-way conversation via servers– XML ‘stanzas’ – e.g. chat or info/query messages– Servers can be federated (eg. Google Talk) or
standalone (eg. Hyves.nl)
XMPP in a nutshell…
• Developed and deployed for 10+ years• XML-based protocol for IM (chat, buddylists, real time messaging)• Almost entirely unlike SOAP and IRC (but a bit like both)• Used in products from Google, Apple and tools like GAIM/Pidgin• Healthy range of toolkits – servers, clients and libraries• All Google accounts; all Hyves accounts, …• Bewildering and impressive range of extensions (XEPs), e.g.• XEP-0166: Jingle, ‘peer-to-peer media sessions’ (e.g. Google Talk)• XEP-0060: Publish-Subscribe• XEP-0174: Local LAN dns-based discovery and point-to-point links • XEP-0059: Result Set management• XEP-0235: OAuth Over XMPP• XEP-0045: Multi-User Chat• XEP-0275: ‘Entity reputation’• many more…
Why care?
• XMPP can go where HTTP doesn’t• bots, scripts and services can act for their
human users• XMPP’s ‘social graph’ interconnect sites (like
email and FOAF, and unlike closed and proprietary ‘social networks’)
• Friendly and energetic developer community• Save your time for inventing new things
What does it look like?
• Two experimental uses:• Jqbus SPARQL experiments (FOAF project)• ‘NoTube Network’ ideas for TV remotes (NoTube EU)
• Jqbus showed an experimental binding of RDF query (SPARQL) to XMPP
• How else can you send queries into home or laptop?• Or filter them based on buddylist rules (colleagues, family)?• Or allow for query results to arrive hours later?
(if you don’t know SPARQL, think of it as SQL-ish query over linked RDF databases)
Jqbus: sending a query
<iq id="S3IG2-4" to="alice.notube@example.com/sparqlserver" type="get">
<query xmlns='http://www.w3.org/2005/09/xmpp-sparql-binding'>
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT DISTINCT ?o WHERE {?s foaf:name ?o.} </query>
</iq> (from bandri@livejournal.com )
Jqbus: a query arrives
<iq id="40z5D-4" to="alice.notube@example.com/sparqlserver" from="bandri@livejournal.com/sparqlclient" type="get">
<query xmlns="http://www.w3.org/2005/09/xmpp-sparql-binding">
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT DISTINCT ?o WHERE {?s foaf:name ?o.}
</query> </iq>
A response is sent…<iq id="40z5D-4" to="bandri@livejournal.com/sparqlclient"
from="alice.notube@example.com/sparqlserver" type="result"> <query-result xmlns="http://www.w3.org/2005/09/xmpp-sparql-
binding"> <sparql xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xs="http://www.w3.org/2001/XMLSchema#" xmlns="http://www.w3.org/2005/sparql-results#">
<head><variable name="o"/> </head> <results> <result> <binding name="o"> <literal>Libby Miller</literal>
</binding> </result> <result> <binding name="o"> <literal>Tim Berners-Lee</literal>
</binding> </result> <!-- ... more bindings here --> </results> </sparql> </query-result> </iq>
…and is received.
• Messages can be directed or general– Eg: to danbrickley@gmail.com or to– danbrickley@gmail.com/photo_database
• Can be real-time or delayed• Have practical limits on message size– These SPARQL bindings should be redone– Jingle specs help with bulky data and direct links
Eg. 2: “Buttons” (NoTube Network)
• Work-in-progress ‘smart remote control’ protocol• XMPP as controlled route thru NAT/firewall• Attached to desktop ‘media centre’ software:– Boxee / XBMC / Plex (TV-like full screen media)– MythTV (linux-based PVR, uses DVB-T USB for TV)– EyeTV (applescript-able OSX tool, also DVB-T)– MediaPortal (Opensource C# software)– Windows Media Centre (with .NET SDK)– Itunes (applescript-able on OSX)
What do these all have in common?
• A lot but not enough: chaos of different media-centre APIs and schemas
• Remotes tend to be dumb: sending clicks not commands, and no return-path for data…
• APIs allow basic navigation, play/pause, screenshot, EPG access, but via local PC or LAN
• Can diverse media centres share an API?– Can we expose it over XMPP? – Use it from smartphones? Multi-touch tables?
<iq to="alice.notube@gmail.com/0AEDD375" type="result"><query xmlns="jabber:iq:roster"><item jid="bob.notube@gmail.com" subscription="both”><item jid="buttons@foaf.tv" subscription="both"/><item jid="danbrickley@gmail.com" subscription="both”><item jid="libby.miller@gmail.com" subscription="both"/><item jid="yves.example @gmail.com" subscription="both"/>
</query></iq>
A remote control with a buddylist?
Maybe.
• Prototyped at the play/pause/ffwd level• With Strophe.js and BOSH, can do HTML5 too!• Can control Boxee and MythTV via XMPP– Sample client running on iphone– Server attached to xmpp:buttons@foaf.tv– Remote attached to xmpp:bob.notube@gmail.com– Very often super-fast; sometimes awkwardly slow– Can we drop down from server-mediated comms?
Maybe.
• XEP-0174 defines local network discovery– And point-to-point XMPP comms (ie. not via gtalk!)– As used in Apple’s Bonjour iChat local chat– The Jingle specs also relevant here
• Other tricks for faster UI?– Iphone motion sensor – if it’s moving, send a ping– Design a protocol that sends commands not clicks• But beware downloading megabytes of EPG TV data
Service Discovery
• Web service discovery for real?– Which of my buddys have VOIP support? Video?– Which have RDF databases online?– Or a TV / media centre connected?
• Which are on same LAN as me?• How do we manage permissions for all this?
Presence and capabilities
<presence from=”example.buddy@gmail.com/BitlBee82551989" to="alice.notube@gmail.com/0AEDD375">
[…] </presence>
<caps:c node="http://mail.google.com/xmpp/client/caps" ver="1.1" ext="pmuc-v1 sms-v1" xmlns:caps="http://jabber.org/protocol/caps"/>
Summary
• XMPP – the basics just work– Lots of libraries / tools– Helpful, friendly community– Focal point for problem-sharing
• Tread carefully– Navigating the maze of interesting extensions– Guessing which toolkit to bet on for your needs– Learning the landscape and what to rely on
Questions?
• Or to danbri@few.vu.nl
• MythTV / iChat demo: Libby Miller• Draft iPhone graphics: Vicky Buser• NoTube project: www.notube.tv