IRC log of rdb2rdf on 2010-10-21
Timestamps are in UTC.
- 18:11:52 [RRSAgent]
- RRSAgent has joined #rdb2rdf
- 18:11:52 [RRSAgent]
- logging to http://www.w3.org/2010/10/21-rdb2rdf-irc
- 18:12:00 [betehess]
- trackbot, start meeting
- 18:12:00 [trackbot]
- Sorry... I don't know anything about this channel
- 18:12:00 [trackbot]
- If you want to associate this channel with an existing Tracker, please say 'trackbot, associate this channel with #channel' (where #channel is the name of default channel for the group)
- 18:12:09 [betehess]
- RRSAgent, draft minutes
- 18:12:09 [RRSAgent]
- I have made the request to generate http://www.w3.org/2010/10/21-rdb2rdf-minutes.html betehess
- 18:12:15 [betehess]
- scribe: betehess
- 18:12:29 [juansequeda]
- http://www.w3.org/2001/sw/rdb2rdf/wiki/All_Cases_for_Default_Mapping
- 18:12:33 [juansequeda]
- http://www.w3.org/2001/sw/rdb2rdf/directGraph/
- 18:12:59 [betehess]
- @@: section 2
- 18:13:24 [betehess]
- ... what happens with the PrimaryKey?
- 18:14:15 [betehess]
- ... @enumerates 7 cases that have to be treated@
- 18:17:35 [betehess]
- ericP: the FK points to a CandidateKey in another table, but ti does not mean it's a PK
- 18:17:47 [betehess]
- ... or even that there is a PK
- 18:18:22 [betehess]
- @@: is that the only case you need both tables?
- 18:18:25 [betehess]
- ericP: ye
- 18:19:01 [betehess]
- @@: let's write down any single case in specific sections
- 18:19:19 [betehess]
- Zakim, who is noisy?
- 18:19:31 [Zakim]
- betehess, listening for 10 seconds I heard sound from the following: Marcelo (94%), EricP (44%)
- 18:20:09 [betehess]
- ericP: the recipe should tell you what it has to do
- 18:20:21 [betehess]
- ... the examples give you a sense of what it does
- 18:21:27 [betehess]
- ... if you don't want to have separate examples for each case, you can just say: "this example covers these cases"
- 18:21:38 [betehess]
- ... because some cannot exist on their own
- 18:21:48 [betehess]
- q+
- 18:22:32 [betehess]
- +1
- 18:24:57 [betehess]
- ericP: let's be sure we agree on the examples
- 18:26:15 [betehess]
- Marcelo: the use-cases are ok, the examples too
- 18:26:23 [betehess]
- ... it's just difficult to read
- 18:26:40 [Zakim]
- +OpenLink_Software
- 18:26:42 [betehess]
- ... I propose myself to re-organize for next week
- 18:26:48 [MacTed]
- Zakim, OpenLink_Software is me
- 18:26:49 [Zakim]
- +MacTed; got it
- 18:26:56 [betehess]
- ericP: what about terminology?
- 18:27:03 [betehess]
- ... tables VS relations
- 18:27:23 [MacTed]
- Zakim, mute me
- 18:27:23 [Zakim]
- MacTed should now be muted
- 18:27:50 [betehess]
- ... SQL can give you multiple columns with the same name
- 18:28:00 [betehess]
- ... you cannot do it with SPARQL
- 18:28:06 [betehess]
- ... because @@
- 18:28:34 [betehess]
- ... so we have to decide what to do with headers and columns with the same name
- 18:29:40 [betehess]
- juansequeda: can we vote to use SQL terminology instead of relational algebra terminology?
- 18:29:50 [MacTed]
- Zakim, unmute me
- 18:29:50 [Zakim]
- MacTed should no longer be muted
- 18:30:56 [betehess]
- ... choices are: relations/attributes OR tables/columns OR tables/attributes
- 18:31:17 [MacTed]
- tables/columns.
- 18:31:36 [betehess]
- ericP: and we can speak about fnames instead of order
- 18:31:59 [betehess]
- [ betehess: tables/columns ]
- 18:32:12 [MacTed]
- saying "relation = table" doesn't make sense to me. mixing tables/attributes makes even less.
- 18:32:36 [Marcelo]
- relations/attributes
- 18:33:22 [betehess]
- @@: in relation algebra, people use "relation"
- 18:33:56 [betehess]
- @@: in any of my classes, I apologize because the names are not fully defined
- 18:34:29 [betehess]
- RRSAgent, please draft minutes
- 18:34:29 [RRSAgent]
- I have made the request to generate http://www.w3.org/2010/10/21-rdb2rdf-minutes.html betehess
- 18:34:53 [betehess]
- @@: I would suggest to use SQL terminology because of the audience
- 18:35:33 [betehess]
- PatH: we at least need to define the terms very well
- 18:35:58 [MacTed]
- +1
- 18:36:03 [Marcelo]
- +1
- 18:36:08 [betehess]
- Consensus around SQL terminology
- 18:36:14 [betehess]
- ericP: +1
- 18:36:23 [juansequeda]
- +1 for using SQL terminology
- 18:36:45 [PatH]
- abstain. I go with the flow.
- 18:37:37 [betehess]
- @@: SQL people use column, not attributes
- 18:38:25 [betehess]
- @@: can we say: tables + columns + columns are unique within the table?
- 18:38:26 [MacTed]
- SQL identifiers == catalog.owner/schema.table.field
- 18:38:49 [MacTed]
- s/field/column/
- 18:39:25 [betehess]
- ericP: the schema has a unique mapping from to datatypes
- 18:39:26 [MacTed]
- column names are unique within table; table names are unique within owner/schema; owner/schema names are unique within catalog
- 18:39:38 [betehess]
- ... tuple has unique mapping from names to value (or NULL)
- 18:40:41 [betehess]
- ... Marcelo and I propose a clearer version of the document
- 18:41:00 [betehess]
- ... expecting others will understand how genius we are :-)
- 18:41:21 [Marcelo]
- http://www.w3.org/2001/sw/rdb2rdf/directGraph/
- 18:42:59 [betehess]
- ericP proposed a strategy for editing the documents
- 18:46:57 [betehess]
- betehess: what is semantics?
- 18:47:14 [betehess]
- ericP: you take an RDB and then you have an RDF graph
- 18:47:53 [betehess]
- ... it's all about the formalism of the formal mapping
- 18:50:20 [betehess]
- [[
- 18:50:21 [betehess]
- given a SPARQL-to-SQL mapping to access SQL database, prove that the semantics of the translated SPARQL query executed against a particular RDB dataset is equivalent to the same SPARQL query executed against the same RDB dataset seen through the RDB2RDF mapping.
- 18:50:22 [betehess]
- ]]
- 18:50:31 [PatH]
- +1 to whoever just spoke.
- 18:51:20 [PatH]
- Yes, we should do this. BUt this is about the semantics of the inputs and outputs of the mapping, not of the mapping language itself.
- 18:51:31 [betehess]
- PatH, yes :-)
- 18:51:48 [Marcelo]
- +1 PatH
- 18:55:47 [Zakim]
- -EricP
- 18:56:22 [betehess]
- 1. in the case of the Default Mapping, you have a function "mapping : RDB → RDF".
- 18:56:32 [betehess]
- 2. in the case of R2ML, you have a function "mapping : (RDB×R2ML) → RDF". The Default Mapping is just a particular case where you use the empty value as an inhabitant for R2ML.
- 18:57:19 [PatH]
- We could (not on IRC) draw this as a 'square' of functors which we want to commute.
- 18:57:24 [MacTed]
- +10000000 :-)
- 18:58:03 [PatH]
- BTW, I think this might be quite tricky to establish, I think. It *ought* to be easy, but details, details...
- 19:00:24 [PatH]
- Seems to me that there will be a big semantic mismatch arising from the 'open world' assumption (semantic: classical model thoery) of RDF. Have you guys discussed this?
- 19:00:51 [juansequeda]
- PatH, we haven't
- 19:01:05 [PatH]
- Oh.
- 19:02:45 [MacTed]
- PatH - not sure what issue you're seeing....
- 19:02:45 [MacTed]
- RDB ("schema first") is generally considered a 'closed world' model.
- 19:02:45 [MacTed]
- RDF ("schema last") is generally considered an 'open world' model.
- 19:02:46 [MacTed]
- 'closed world' fits fine within 'open world', which is what we're doing. RDB exposed as *part of* the RDF GGG.
- 19:03:26 [PatH]
- Yes, but if we try to establish semantic relationship using the semantics, we will find that RDF cannot express things that are implicit in the RDB semantic model.
- 19:03:40 [MacTed]
- example, please?
- 19:04:19 [PatH]
- Implied negatives for missing data, for example, which can be detected by SPARQL.
- 19:04:50 [PatH]
- Semantically, closed world is much stronger than open.
- 19:05:09 [PatH]
- stronger = fewer models, more implications.
- 19:05:43 [MacTed]
- can you state the problem you see more explicitly? I'm not seeing the issue you apparently are.
- 19:07:09 [PatH]
- Might take too long on IRC. Need a fully worked out example. Semantically, its that minimal models or algebraic semantics can express many things that cant be expressed in RDF wihtout negation.
- 19:10:17 [MacTed]
- so ... they can be expressed in RDF *with* negation, yes? or in RDF with "affirmative statement of negative"?
- 19:10:19 [PatH]
- Such things as: negative queries following from failure to find a match. And cardinality queries like 'how many'. None of this follows in the RDF semantics.
- 19:10:43 [PatH]
- But RDF doesnt have negation!
- 19:10:54 [MacTed]
- I think you're shifting from RDF to SPARQL, and from RDB to SQL
- 19:11:17 [MacTed]
- <a> hasNo <b> -- affirmative statement of negation :-)
- 19:11:19 [PatH]
- No, thats the problem. SPARQL can do things that arent supported by the RDF *semantics*.
- 19:11:35 [Zakim]
- -MacTed
- 19:11:40 [Zakim]
- -PatH
- 19:11:41 [Zakim]
- -Alexandre
- 19:11:49 [Zakim]
- -juansequeda
- 19:11:49 [betehess]
- RRSAgent, draft minutes
- 19:11:49 [RRSAgent]
- I have made the request to generate http://www.w3.org/2010/10/21-rdb2rdf-minutes.html betehess
- 19:11:54 [Zakim]
- -Marcelo
- 19:11:55 [Zakim]
- Team_(RDB2RDF)18:03Z has ended
- 19:11:57 [Zakim]
- Attendees were PatH, Marcelo, Alexandre, juansequeda, EricP, MacTed
- 19:12:30 [betehess]
- are the minutes of this WG public?
- 19:12:47 [betehess]
- I mean, world readable?
- 19:12:59 [MacTed]
- I'm clearly not grasping something.
- 19:13:06 [betehess]
- do you guys need to authenticate to access the other minutes?
- 19:13:56 [MacTed]
- RRSAgent, make minutes public
- 19:13:56 [RRSAgent]
- I'm logging. I don't understand 'make minutes public', MacTed. Try /msg RRSAgent help
- 19:14:09 [betehess]
- arf, I did it manually :-)
- 19:14:16 [MacTed]
- *heh*
- 19:14:17 [betehess]
- it's ok
- 19:14:41 [betehess]
- and I will write briefly about the last part as I wans't scribing
- 20:34:10 [betehess]
- minutes and semantics discussion available at http://lists.w3.org/Archives/Public/public-rdb2rdf-wg/2010Oct/0070.html
- 20:34:29 [betehess]
- my theorem is not well-typed but you get it :-)
- 20:54:04 [Zakim]
- Zakim has left #rdb2rdf
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- MacTed has joined #RDB2RDF