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XSPARQL: Traveling between the XML and RDF worlds - and avoiding the XSLT Pilgrimage
Data Model and Query Constructs for Versatile Web Query Languages
As the Semantic Web is gaining momentum, the need for
truly versatile query languages becomes increasingly apparent. A Web
query language is called versatile if it can access in the same query program
data in different formats (e.g. XML and RDF). Most query languages
are not versatile: they have not been specifically designed to cope
with both worlds, providing a uniform language and common constructs
to query and transform data in various formats. Moreover, most of them
do not provide a flexible data model that is powerful enough to naturally
convey both Semantic Web data formats (especially RDF and
Topic Maps) and XML. This article highlights challenges related to the
data model and language constructs for querying both standard Web
and Semantic Web data with an emphasis on facilitating sophisticated
reasoning. It is shown that Xcerpt’s data model and querying constructs
are particularly well-suited for the Semantic Web, but that some adjustments
of the Xcerpt syntax allow for even more effective and natural
querying of RDF and Topic Maps
SWI-Prolog and the Web
Where Prolog is commonly seen as a component in a Web application that is
either embedded or communicates using a proprietary protocol, we propose an
architecture where Prolog communicates to other components in a Web application
using the standard HTTP protocol. By avoiding embedding in external Web servers
development and deployment become much easier. To support this architecture, in
addition to the transfer protocol, we must also support parsing, representing
and generating the key Web document types such as HTML, XML and RDF.
This paper motivates the design decisions in the libraries and extensions to
Prolog for handling Web documents and protocols. The design has been guided by
the requirement to handle large documents efficiently. The described libraries
support a wide range of Web applications ranging from HTML and XML documents to
Semantic Web RDF processing.
To appear in Theory and Practice of Logic Programming (TPLP)Comment: 31 pages, 24 figures and 2 tables. To appear in Theory and Practice
of Logic Programming (TPLP
Trusty URIs: Verifiable, Immutable, and Permanent Digital Artifacts for Linked Data
To make digital resources on the web verifiable, immutable, and permanent, we
propose a technique to include cryptographic hash values in URIs. We call them
trusty URIs and we show how they can be used for approaches like
nanopublications to make not only specific resources but their entire reference
trees verifiable. Digital artifacts can be identified not only on the byte
level but on more abstract levels such as RDF graphs, which means that
resources keep their hash values even when presented in a different format. Our
approach sticks to the core principles of the web, namely openness and
decentralized architecture, is fully compatible with existing standards and
protocols, and can therefore be used right away. Evaluation of our reference
implementations shows that these desired properties are indeed accomplished by
our approach, and that it remains practical even for very large files.Comment: Small error corrected in the text (table data was correct) on page
13: "All average values are below 0.8s (0.03s for batch mode). Using Java in
batch mode even requires only 1ms per file.
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