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Re: Linked Data Fragments: Web-scale querying

From: Olaf Hartig <ohartig@uwaterloo.ca>
Date: Wed, 19 Mar 2014 10:03:39 -0400
To: <public-lod@w3.org>, "semantic-web@w3.org Web" <semantic-web@w3.org>
CC: Martynas Jusevičius <martynas@graphity.org>
Message-ID: <3525543.ZbR3tUVqXI@porty2>
Hi Martynas,

On Wednesday 19 March 2014 12:58:15 Martynas Jusevičius wrote:
> Ruben,
> interesting stuff. I remember another project that does something like that:
> SQUIN http://squin.sourceforge.net/index.shtml

SQUIN implements a traversal-based query execution strategy that relies only 
on the Linked Data publishing principles (i.e., the possibility to look up 
HTTP URIs). Query processing approaches that have this property are typically 
referred to as Linked Data query processing. If you want to get an overview on 
these approaches, you may want to check out my recent survey [1].

> How does LDF compare to to it?

I understand LDF more as an alternative practice for publishing (Linked) data 
on the Web. However, the primary purpose for proposing this practice (as Ruben 
and his colleagues emphasize in their LDOW paper) his to facilitate 
distributed querying without putting most of the burden on the servers.

So, the primary difference between querying LDFs and the aforementioned Linked 
Data query processing is that querying LDFs is a form of distributed query 
processing, that is, some part of the execution of a given user query is 
distributed to LDF servers (which provide a limited form of query processing 
functionality). In contrast, Linked Data query processing  is _not_ a form of 
distributed query processing. Instead, for Linked Data query processing 
approaches, the whole execution of a query happens within the Linked Data 
query processing system (e.g., SQUIN), simply because these approaches do not 
assume / rely on server-side query processing functionality (servers in this 
setting are only required to answer URI lookup requests).


[1] Olaf Hartig: An Overview on Execution Strategies for Linked Data Queries. 
In Datenbankspektrum, 13(2) Jul. 2013.

> Thanks,
> Martynas
> graphityhq.com
> ----------------------------- snip --------------------
Received on Wednesday, 19 March 2014 14:04:50 UTC

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