Thanks, John, for the explanation(s). I understand the idea. Essentially, the meaning of wikitext would then depend on when exactly a page is stored. The same content could have different meaning. That seems problematic to me ... But I guess we don't have to worry since it seems clear that this won't be implementable in MediaWiki as we know it today ;-) But thanks anyway -- it's an interesting concept, even if purely hypothetical right now.
Best regards,
Markus
On 13.07.2015 19:33, John Erling Blad wrote:
Actually I think we have a problem with all three points in the CAP theorem, so we should start coding for fault tolerance. Still this goes off-topic. I'm done with this thread.
On Mon, Jul 13, 2015 at 6:29 PM, John Erling Blad jeblad@gmail.com wrote:
A property function for versioned labels would look _exactly_ the same as today, but the request for the actual value would use the label and a timestamp. The timestamp would be the last revision of the template.
Look up books on distributed databases, and check out how they maintain consistency. In our case it is a simplified set up with a single master server with multiple clients that has read access to the server. In addition they have their own state that interfere with the master state.
We have a consistency problem (CAP theorem) because the clients don't update their state (the templates) according to changes on the server (the labels). One solution to this is to keep the last known version (a timestamp) to make it possible to continue using outdated information.
Another way to say this is that a change in the label leaves an invalid state at the clients, because the transaction ends prematurly. That is the templates are not updated, which they must be if the system lacks versioning.
Even another way to describe this is that the process running on the server and the clients lacks isolation, which again can be restored with versioning.
There are several consistency models that can be used, but I don't know if anyone includes something like the proposed "alias model".
CAP theorem is described in these two, but I havn't read them, sorry for that!
Brewer, Eric A.: Towards robust distributed systems (abstract), in: Proceedings of the nineteenth annual ACM symposium on Principles of distributed computing, PODC’00, ACM, New York, NY, USA, pp. 7–
Gilbert, Seth and Lynch, Nancy: Brewer’s conjecture and the feasibility of consistent, available, partition-tolerant web services. SIGACT News (2002), vol. 33:pp. 51–59
On Mon, Jul 13, 2015 at 4:21 PM, Markus Krötzsch markus@semantic-mediawiki.org wrote:
On 13.07.2015 16:01, John Erling Blad wrote:
No we should not make the aliases unique, the reason aliases are useful is because they are _not_ unique. Add versioning to labels, that is the only real solution.
Following this thread for a while, I still have no idea what this solution is. Could you give an example of how the #property function in Wikitext will look for this proposal?
There are books on the topic, and also some dr thesis. I don't think we should create anything ad hoc for this. Go for a proven solution.
Citation needed ;-)
Markus
On Mon, Jul 13, 2015 at 3:24 PM, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Am 13.07.2015 um 13:00 schrieb Ricordisamoa:
I agree too. Also note that property IDs are language-neutral, unlike english names of templates, magic words, etc.
As I said: if there is broad conseus to only use P-numbers to refer to properties, fine with me (note however that Lydia disagrees, and it's her decision). I like the idea of having the option of accessing properties via localized names, but if there is no demand for this possibility, and it's a pain to implement, I won't complain about dropping support for that.
But *if* we allow access to properties via localized unique labels (as we currently do), then we really *should* allow the same via unique aliases, so property labels can be chanegd without breaking stuff.
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
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