[DAIS-WG] RDF Specification Motivation Text

[Oscar Corcho]

Steven,

I think that you have made a good job with the motivation.

Oscar

-----Mensaje original-----
De: dais-wg-bounces at ogf.org [mailto:dais-wg-bounces at ogf.org] En nombre de
Steven Lynden
Enviado el: martes, 07 de julio de 2009 11:00
Para: dais-wg at ogf.org
Asunto: [DAIS-WG] RDF Specification Motivation Text

Hi,

At the last RDF telcon we decided that it was important to clearly
define the motivation for the RDF specifications. The text below is  a
potential addition to the motivational document to do this. Any
comments/additions welcome, especially about points that might not be
valid or things that have been missed.

Regards,

Steven.

This document proposes extending the WS-DAI specifications, currently
including XML and relational realisations, to encompass RDF(S) data
resources. Standards for accessing databases from programming
languages (e.g. JDBC, XML:DB etc) have been widely used to save
programming effort and promote interoperability and the WS-DAI
specifications bring the same benefits to service-based computing. The
WS-DAI specifications provide a set of WSDL interfaces for managing,
querying and describing various properties associated with data
resources, an important aspect of this approach being that the
interfaces defined in the WS-DAI specifications can be seamlessly
combined with those defined by other web service standards that
concentrate on other areas, for example, security. Although the SPARQL
query language already has an associated W3C recommendation web
service-based protocol [SPARQL-Protocol] for executing SPARQL queries,
the RDF(S)-based WS-DAI specifications described in this document are
required for the following reasons:

- The WS-DAI specifications set out standard patterns for querying,
managing and describing various aspects of data resources within the
context of service-based computing, for example operations exist for
configuring data resources and describing a data resource's ability to
support various features such as transactions. In contrast, the SPARQL
Protocol defines a single query operation and associated fault
messages but lacks the range of operations, properties and faults
defined within WS-DAI in order to fully support access to data
resources in a service-based setting. An RDF(S) realisation of WS-DAI
is therefore required to provide this support in an RDF(S) setting.

- The SPARQL Protocol's SparqlQuery::query operation is analogous to
the direct data access query pattern specified by WS-DAI, where the
entire dataset formed as the result of a query is returned to a client
within a response message. The WS-DAI specification defines a second
pattern, indirect data access, where the result of a query is made
available as a new data resource, i.e. implementing the factory
pattern. This pattern supports third-party delivery, can be used to
avoid unnecessary data movement, and allows a client to pull data from
a data resource rather than have it returned all at once in a single
response message. This access pattern is important in a wide range of
scenarios including distributed query processing and providing
scalable/reliable data access.

- WS-DAI specifications exist for XML and relational data sources, and
their adoption will result in applications that follow the WS-DAI
approach to using data resources in a service-based setting. There is
therefore a need to 'complete' the set of specifications in order to
complement the XML and relational realisations, enabling applications
and developers familiar with using WS-DAIR and WS-DAIX to interact
with RDF(S) data resources using the same approach. Currently, RDF(S)
data is widely used and its adoption is growing, this means that the
next logical progression is to concentrate DAIS-WG efforts in this
area.

-  The SPARQL query language is not the only means by which a client
may wish to interact with an RDF(S) data resource. The interfaces
provided by RDF(S) storage systems, for example the Jena Ontology API,
provide a a range of mechanisms for directly manipulating an ontology.
As such APIs vary depending on the specific storage system used, for
example Oracle RDF, Sesame etc., the WS-DAI-RDF(S) Ontology
specification aims to provide a set of ontology handling primitives
for interacting with RDF(S) data resources, hiding any syntactic and
platform-dependent aspects, enabling their use in an open,
interoperable way.
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