Information Technology Reference
In-Depth Information
In the above example,
vra:Image
(which is a class defined by Visual Resource
Association [17]) is used to fix the domain of
wi:#url
slot to image URLs. The
domain of
wm:#url
slot is also fixed to URLs of resources in general by using
rdfs:Resource
. By using this additional information about slot value domains,
we can check whether values of one slot can be set to another slot by using the
following rule:
x wb:valueDomain s
∧
y wb:valueDomain t
∧
s rdfs:subclassOf t
values of slot
x
can be set to slot
y
In this paper, we do not discuss details about webble vocabulary and rules for
controlling behavior of webbles. The main point we would like to emphasise
here is that by introducing application specific type systems and rules, we can
carefully restrict the operations that users can perform. We believe that such
restrictions on user's operations for avoiding misconnections of webbles is useful
and somehow indispensable when we provide webbles for
casual
users.
3Conluon
In this paper we have argued that if the webble technology is to be used in its full
strength it should be enhanced in two ways: (a) providing means for searching
a potentially huge pool of webbles and (b) controlling webble's behavior by
introducing application specific type systems and rules. We have proposed webble
annotations as an unobtrusive way to remedy these two deficiencies of the current
webble technology. Additionally, by studying an important use case (annotation
of digital media contents) we have demonstrated the benefits of using standard,
controlled vocabularies in the definition of webble annotations.
We are currently researching several aspects of composite webbles. The main
concern is query formulation and evaluation for searching webbles in the web-
ble repository. In this paper, we have demonstrated how webble annotations
can be directly mapped to RDF graphs and how our mapping method produces
“clean” RDF graphs of content metadata. Therefore we can search media
con-
tents
in the webble repository by using the same manner for querying content
metadata. However, the question is how to search media
containers
in the same
repository. Webbles may have many slots and sometimes they are composite.
Annotations over such complex webbles are represented as complex RDF graphs
which is dicult to query. To allow typical users to search complex webbles
from the repository, we need to introduce a mechanism for “summarizing” web-
ble annotations into simpler forms to search. We have developed a theoretical
framework of metadata summarization in the context of composite document
repositories [18]. This framework works with metadata comprising a set of terms
from a controlled vocabulary. In future work, we will extend this framework to
handle metadata represented as RDF graphs.
