W3C home > Mailing lists > Public > public-prov-wg@w3.org > October 2011

Re: writing a simple example in prov-o, help

From: Simon Miles <simon.miles@kcl.ac.uk>
Date: Wed, 26 Oct 2011 18:38:50 +0100
Message-ID: <CAKc1nHdCbBV=+msGPqH2V1LhktO10isnOb8yBGtQW5OsRRPP8w@mail.gmail.com>
To: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Paul,

I take your point and agree that it would be good to allow these brief
assertions.

I think we will have to be careful about what a lack of
characterisation means. It could read as "weakly characterised, I
provide no guarantees that what I assert is true over
time/perspectives" or read as "strongly characterised but very
general, I don't provide any specific characteristics because what I
assert is true of what is referred to by this URI regardless of
time/perspective". Maybe the intended semantics just needs to be made
clear in the model (if not already).

Also, while it is nice to have a simply expressed statement when we
have simple information, it is also nice to not have to change the way
you model when you realise there's more to say (see EntityInRole
discussion...). So if you say

<http://thinklinks.wordpress.com/2011/07/31/why-provenance-is-fundamental-for-people/>
prov:wasDerivedFrom
<http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.

but then realise that the video has changed to contradict your summary
of it, and want to clarify that you meant the video before editing,
you will not be adding detail (characterisation) to what you asserted
before, but actually removing what was said before and saying
something different (because you cannot add detail to a URL you do not
control).

Thanks,
Simon

On 26 October 2011 11:14, Paul Groth <p.t.groth@vu.nl> wrote:
> Hi Simon,
>
> I actually don't think there's anything wrong with using entities that are not characterized in detail (e.g. Those using only a URL attribute). If you use a URL that happens to change your characterization is not specific but still valid. So I choose option c) I use the URL I like to refer to the video. If the content at that url changes well that's fine my provenance is just not as specific as maybe one would like.
>
> We can encourage people to use detailed characterizations but there's no reason to be pedantic.
>
> Paul
>
> On Oct 26, 2011, at 11:53, Simon Miles <simon.miles@kcl.ac.uk> wrote:
>
>> Hi Paul,
>>
>> I think the argument you make is the same as implied by my example...
>> except that the conclusion is different.
>>
>> As you say, the provenance best practice could be to use permalinks.
>> So, in the example, the bloggers should use permalinks. They have no
>> control over what the original YouTube URL deferences to, so cannot
>> ensure it is a permalink. Unless they have special information, they
>> can only assume it is not, and so either they:
>>  (a) cannot say anything about the video at all, or
>>  (b) need to create their own permalink to refer to the video.
>> If doing (b), this new URI clearly should connect to the YouTube URL
>> as it is the video that the provenance is about. However, to make it
>> into a permalink, there must be something more which ensures it always
>> describes the same content, i.e. characterisation of the entity. The
>> provenance then looks like the PROV-OM examples rather than the simple
>> link.
>>
>> I'm not clear if you are arguing for option (a) in your email, i.e.
>> limit people to only refer to things in their provenance when they can
>> control those thing's immutability, but this seems very restrictive.
>>
>> I'm not saying I prefer the long-winded provenance data, just that it
>> appears the desire for interoperability makes it necessary beyond
>> limited cases.
>>
>> I think accounts and consistency are tangential issues - there is
>> nothing inconsistent in what is asserted, the inconsistency comes only
>> from the ambiguity of what is being asserted about.
>>
>> Thanks,
>> Simon
>>
>>> The point is that two different people are asserting it. We can't
>>> maintain consistency across the people. This is why we have accounts, no?
>>>
>>> I think one way to handle this is to have a best practice where we
>>> suggest people use permalinks (see
>>> http://en.wikipedia.org/wiki/Permalink) or cool-uris.  Indeed, to me
>>> this is probably the best way to introduce entities.
>>>
>>> So overall, my suggestion would be to maintain simplicity but suggest
>>> people use uris that refer to content that doesn't change.
>>>
>>> But please bring this up in interoperability page.
>>>
>>> cheers,
>>> Paul
>>>
>>>
>>>
>>> Simon Miles wrote:
>>>> Paul, all,
>>>>
>>>> Just to properly understand why what is being discussed is important,
>>>> I wanted to expand your example to a larger use case.
>>>>
>>>> At time T, you say something about a video on your blog and assert:
>>>> <http://thinklinks.wordpress.com/2011/07/31/why-provenance-is-fundamental-for-people/>
>>>> prov:wasDerivedFrom
>>>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>>>>
>>>> At time T+1, the video is edited to introduce a previously missing
>>>> segment that undermines the message of your blog entry. The video URI
>>>> stays the same.
>>>>
>>>> At time T+2, I say something about the (updated) video on my blog and assert:
>>>> <http://inkings.org/2011/10/08/why-provenance-is-pointless/>
>>>> prov:wasDerivedFrom
>>>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>>>>
>>>> We could then observe:
>>>>   - Even if the above use case doesn't happen to you, by using the
>>>> simplest form of provenance you are opening the possibility of it
>>>> happening and you would not even know about it.
>>>>   - It doesn't help to say that the video owners shouldn't use the same
>>>> URL, because it is not under the control of either those creating or
>>>> consuming the provenance.
>>>>   - There is nothing apparently wrong with either of our assertions
>>>> (except the lack of characterisation), and I don't know anything about
>>>> your blog so don't take it into account in my blog's provenance.
>>>>   - It seems reasonable criteria for interoperability that if you read
>>>> Prov-DM from two separate sources referring to the same entity, then
>>>> either there is an error in (at least) one or they are mutually
>>>> consistent. I couldn't see what this would correspond to in the
>>>> interoperability discussion [1] though.
>>>>
>>>> Thanks,
>>>> Simon
>>>>
>>>> [1] http://www.w3.org/2011/prov/wiki/Interoperability
>>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> Dr Simon Miles
>> Lecturer, Department of Informatics
>> Kings College London, WC2R 2LS, UK
>> +44 (0)20 7848 1166
>>
>



-- 
Dr Simon Miles
Lecturer, Department of Informatics
Kings College London, WC2R 2LS, UK
+44 (0)20 7848 1166
Received on Wednesday, 26 October 2011 17:39:21 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 13:06:46 GMT