RE: Question for DCAT "experts"

In my experience, this scenario – where a data publisher makes available a sequence of update files that encode incremental changes from some initialising “complete” publication – is the pre-dominant pattern of data exchange in the financial information domain (outside the streaming/realtime data delivery) so it’s one that we’re extremely interested in.  We’d like to be able to leverage DCAT as much as possible though clearly we may be extending into a more specialised vocabulary beyond what’s appropriate for inclusion in the DCAT standard itself.  As an example, we’d like to be able to automatically process  the sequence of files by using the metadata as configuration information so that a data consumer could create a local replica of the latest state of the published data. Our current thinking actually aims to handle this at the dct:Distribution level – though this is still active work and we haven’t yet settled on a definite approach.

As Andrea says, from a data consumer’s perspective, there’s some kind of link here with how service-based access might be modelled, since in my experience that’s often used to give access to  a ‘latest state/current value’ copy of the data.  [Of course, that might not be the direction the WG takes....]

So I’d like to see this considered as a potential use case for discussion  till we have a fuller understanding of the landscape.

Last comment:  we tend to think of this kind of change - “more data” – as somewhat distinct from version changes.  A version change typically  indicates something potentially more disruptive to a consumer than an update file.  And, yes, there is some ambiguity in that distinction – but in practice it’s been a useful distinction in our environment.

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From: andrea.perego@ec.europa.eu [mailto:andrea.perego@ec.europa.eu]
Sent: 22 June 2017 14:15
To: public-dxwg-wg@w3.org
Cc: marvin.frommhold@eccenca.com; martin.bruemmer@eccenca.com; makx@makxdekkers.com; Peter.Winstanley@gov.scot; kcoyle@kcoyle.net
Subject: RE: Question for DCAT "experts"

I think it may be worth considering whether the scenario outlined by Karen ("incremental updates"?) relates also to the notion of dcat:Distribution. In particular, for the mechanism used to for synchronising data version, I see some relationship with the use cases concerning the modelling of service-based data access.

Andrea

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From: Martin Brümmer [mailto:martin.bruemmer@eccenca.com]
Sent: Thursday, June 22, 2017 11:35 AM
To: public-dxwg-wg@w3.org<mailto:public-dxwg-wg@w3.org>
Cc: Marvin Frommhold
Subject: Re: Question for DCAT "experts"


Hi there,

a colleague of mine, Marvin Frommhold, is researching versioning in the context of RDF and Linked Data. He contributes the following points:

The following two documents provide a basic introduction to versioning of datasets:

  *   Papakonstantinou, Vassilis et al. “Versioning for Linked Data: Archiving Systems and Benchmarks.” BLINK@ ISWC. users.ics.forth.gr, 2016. Web.<https://urldefense.proofpoint.com/v2/url?u=http-3A__ceur-2Dws.org_Vol-2D1700_paper-2D05.pdf&d=DwMGaQ&c=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY&r=SX6sxEGBIuiEtjQTAWz7jTpuOC0f5DcH79errOWxM8RN6gOsHdAxWfl9GTTkalJj&m=HNtxqmdvLjHJ6tDtUN0D71McOaqYoN3CtITnvzqcPmg&s=-ToimaJTj9bR0AuWNhNZ00_s2nfj0f0YTogpBj-wxdc&e=>

     *   Section 2 of this paper provides an introduction of different archiving strategies.

  *   Gray, Alasdair J. G. et al. “Dataset Descriptions: HCLS Community Profile.” Interest group note, W3C (May 2015) http://www.w3.org/TR/hcls-dataset (2015): n. pag. Print.<https://www.w3.org/TR/hcls-dataset/>

     *   A W3C Interest Group Note that, among other things, discusses requirements for dataset versioning.
     *   "The Data Catalog Vocabulary (DCAT) [DCAT<https://www.w3.org/TR/hcls-dataset/#DCAT>] is used to describe datasets in catalogs, but does not deal with the issue of dataset evolution and versioning."
He agrees that change sets are related to versioning in that a version can be described as a set of changes. Fully realized, this allows very granular tracking of dataset evolution. Makx point is important here: These changes are granular descriptions about the evolving content of a dataset, where DCAT so far does little to describe the data itself. If DCAT started to describe the content and structure of the data, this would be a considerable expansion of its scope.

The question if a set of changes constitute a new dataset or if a whole database is a dataset is complicated to me, because I understand instances of dcat:Dataset as conceptual descriptions of datasets, largely independent of the structure of the underlying data. In that sense, a database or a web service independent of the query can also be datasets. Limiting the data retrieved from it by some API call or SQL query could then create a new dataset fully contained in the first one.

cheers,
Martin

Am 22/06/17 um 11:00 schrieb Makx Dekkers:

Yes, I agree it is. Updating 'in place' is a case where the publisher decides that a change does not create a new Dataset.



I find Karen's suggestion to treat a 'database' as a 'dataset' interesting -- I have always thought of a database as closer to a dcat:Catalog.



Makx.





-----Original Message-----

From: Peter.Winstanley@gov.scot<mailto:Peter.Winstanley@gov.scot> [mailto:Peter.Winstanley@gov.scot]

Sent: 22 June 2017 10:52

To: mail@makxdekkers.com<mailto:mail@makxdekkers.com>; public-dxwg-wg@w3.org<mailto:public-dxwg-wg@w3.org>

Subject: RE: Question for DCAT "experts"



isn't a change set (like a diff) just a special case of versioning?



-----Original Message-----

From: Makx Dekkers [mailto:mail@makxdekkers.com]

Sent: 22 June 2017 09:47

To: public-dxwg-wg@w3.org<mailto:public-dxwg-wg@w3.org>

Subject: RE: Question for DCAT "experts"



As far as I remember from the initial work on DCAT, a Dataset is considered to be a kind of blob. Nothing is said about what goes on 'inside' a Dataset. The only thing you see on the outside is the modification date but you don't know what has changed inside.

Makx



-----Original Message-----

From: Karen Coyle [mailto:kcoyle@kcoyle.net]

Sent: 21 June 2017 17:31

To: public-dxwg-wg@w3.org<mailto:public-dxwg-wg@w3.org>

Subject: Question for DCAT "experts"



Many of you know DCAT quite well, and I'm new to it, so I'm taking the lazy way and directing this as a question to you.



I see in DCAT that there are properties that define frequency and update dates. The update date is



"Most recent date on which the dataset was changed, updated or modified."



The library world has a number of databases that are updated "in place".

For anyone receiving updates, the updates do not include the entire file, only those records added, changed, or deleted since some set time.



Is this covered by DCAT? If not, I will add a use case and we can discuss.



Thanks,

kc

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