Databases Reference
In-Depth Information
applies basic rdfs:subClassOf reasoning automatically. After selecting an instance
from the list - or alternatively creating a new one - it is possible to manage (i. e. insert,
edit and update) information in the details view.OntoWiki focuses primarily on the as-
sertion layer, but also provides ways to manage resources on the conceptual layer. By
enabling the visualization of schema elements, called
System Classes
in the OntoWiki
nomenclature, conceptional resources can be managed in a similar fashion as instance
data.
4.4 Authoring
Semantic content in OntoWiki is represented as resource descriptions. Following the
RDF data model representing one of the foundations of the Semantic Web vision, re-
source descriptions are represented (at the lowest level) in the form of
statements
. Each
of these statements (or triples) consist of a
subject
which identifies a resource as well as
a
predicate
and an
object
which together represent data about said resource in a fashion
reminiscent of key-value pairs. By means of RDFa [2], these statements are retained in
the HTML view (i.e. user interface) part and are thus accessible to client-side techniques
like JavaScript.
Authoring of such content is based on said client-side representation by employ-
ing the RDFauthor approach [148]: views are declared in terms of the model language
(RDF) which allows the underlying model be restored. Based on this model, a user
interface can be generated with the model being providing all the domain knowledge
required to do so. The RDFauthor system provides an extensible set of authoring wid-
gets specialized for certain editing tasks. RDFauthor was also extended by adding ca-
pabilities for automatically translating literal object values between di
erent languages.
Since the semantic context is known to the system, these translation functionality can
be bound to arbitrary characteristics of the data (e. g. to a certain property or a missing
language).
ff
Versioning
Evolution.
As outlined in the wiki principles, keeping track of all changes
is an important task in order to encourage user participation. OntoWiki applies this
concept to RDF-based knowledge engineering in that all changes are tracked on the
statement level [10]. These low-level changes can be grouped to reflect application-
and domain-specific tasks involving modifications to several statements as a single ver-
sioned item. Provenance information as well as other metadata (such as time, user or
context) of a particular changeset can be attached to each individual changeset. All
changes on the knowledge base can be easily reviewed and rolled-back if needed. The
loosely typed data model of RDF encourages continuous evolution and refinement of
knowledge bases. With
EvoPat
, OntoWiki supports this in a declarative, pattern-based
manner (cf.[132]).
&
4.5 Access Interfaces
In addition to human-targeted graphical user interfaces, OntoWiki supports a number
of machine-accessible data interfaces. These are based on established Semantic Web
standards like SPARQL or accepted best practices like publication and consumption of
Linked Data.
