15:02:44 RRSAgent has joined #wot-td 15:02:44 logging to http://www.w3.org/2015/06/24-wot-td-irc 15:02:46 RRSAgent, make logs public 15:02:46 Zakim has joined #wot-td 15:02:48 Zakim, this will be 15:02:48 I don't understand 'this will be', trackbot 15:02:49 Meeting: Web of Things Interest Group Teleconference 15:02:49 Date: 24 June 2015 15:03:10 Darko_Anicic has joined #wot-td 15:03:47 DanhLePhuoc has joined #wot-td 15:06:25 dsr has joined #wot-td 15:07:15 meeting: Thing Descriptions 15:07:23 The agenda: 15:07:31 1) Preliminaries 15:07:31 2) Presentation: Standardized and Efficient RDF Encoding (Sebastian Käbisch, Siemens) 15:07:32 3) Plans for use case and requirements discussions 15:07:33 4) Discussion/Brainstorming 15:07:42 Chair: Sebastian 15:07:48 scribenick: dsr 15:08:11 Present: Dave Raggett, Sebastian Kaebisch 15:09:10 Present+ Arne, Ashok Malhotra, Danh Le Phuoc, Daniel Peintner, Darko Anicicm Hamid reza Laleh, Joel 15:09:38 s/Anicicm/Anicic,/ 15:11:17 Sebastian notes that there will be a joint call with the security task force on July 8. 15:11:52 Topic: Standard and Efficient RDF Encoding for Constrained Embedded Networks 15:12:06 Sebastien presents some slides (URI to follow in email) 15:13:29 The challenge is to understand what capabilities/features a given IoT node has. 15:15:03 Interest in using standardised semantic web technologies as a way to address this (RDF, OWL, SPARQL) 15:17:19 There are several existing serialisation formats for RDF, e.g. N-triples RDF/XML, and Turtle. However these can be difficult to support on constrained devices. 15:18:34 Typical IoT sensors have limited functionality and limited network bandwidth. 15:19:07 Data values are typically numbers not strings in order to represent physical values. 15:20:36 There are several approaches to compressing data (slide5 with table) 15:21:43 ZIP isn’t a good fit. CBOR is better, and EXI even better, but at the cost of requirement prior agreement on the data model. 15:22:03 s/prior/of prior/ 15:24:09 EXI is a W3C standard, and ongoing work is making it less dependent on XML 15:26:57 Sebastian presents an RDF/XML example for a temperature and humidity sensor 15:29:47 EXI applies the RDF EXI grammar to create an efficient binary representation of the sensor data 15:33:16 EXI doesn’t require a grammar, but given one can produce better compression. 15:34:53 Slide 10 presents a micro RDF store together with REST messages over CoAP 15:38:25 Slide 11 presents data on compression ratio versus the size of the data set for various different flavours of EXI encoding. 15:41:44 Slide 12 gives data on memory usage for an ARM Cortex M3 chip with 64KB RAM and 256KB ROM 15:43:01 Conclusion: we can combine RDF based semantics with microcontrollers when using EXI 15:44:48 Questions? 15:45:58 Dave: I don’t think we can mandate a single data encoding format, although we can offer advice for helping people to choose for themselves 15:47:40 Dave: secondly, the thing description models which are based upon Linked Data should support efficient encodings 15:48:26 Dave notes that Carsten Bormann is a strong supporter of CBOR and perhaps we should invite his comments. 15:48:49 Sebastian: strings can be a problem for some encodings 15:49:47 Danh: it isn’t clear what you’re using EXI for? 15:50:07 Sebastian: it is mainly for serialisation of data 15:51:32 Moreover, we can store the EXI in a database for efficient storage 15:52:01 Danh: did you do a comparison with binary formats for JSON 15:52:40 Sebastian: EXI tends to do better than some JSON binary encodings due to better handling of strings 15:53:26 Daniel: Qualified names disappear in JSON 15:53:50 CBOR is better than some JSON binary encodings. 15:54:34 Danh: due to MCU resource constraints, regular compression is impractical, right? 15:55:32 Sebastian leaves for a train … 15:56:54 Daniel: for ZIP you need a large buffer while the dictionary is being constructed. EXI avoids that through prior compilation of the grammar 15:57:05 [meeting ends abruptly for scribe] 15:57:06 webex stopped for me 15:57:21 rrsagent, set logs public 15:57:27 rrsagent, make minutes 15:57:27 I have made the request to generate http://www.w3.org/2015/06/24-wot-td-minutes.html dsr 16:02:32 kolchinmax has joined #wot-td 17:30:01 Zakim has left #wot-td 19:36:01 kolchinmax has joined #wot-td