Demos I5 - Evolution and Reactivity
Demonstration of the
Language XChange:
Propagation of Updates on the Web
Many resources on the Web and the semantic Web are dynamic in
the sense that they can change their content over time. The need
for changing (updating) data on the Web has several reasons: new
information comes in, calling for insertions of new data;
information is out-of-date, calling for deletions and replacements
of data. Such changes need to be mirrored by other Web resources
whose data depends on the initial changes. In other words, updates
need to be propagated over related Web resources. The language
XChange has been developed to respond to this need for evolution of
data and reactivity on the Web.
Our use case demonstrates corresponding features of XChange
considering as example several distributed Web resources of the
Eighteenth Century Studies Society (ECSS), a fictitious historical
scientific community. This scenario resembles the "REWERSE
Information System and Portal" as specified in the deliverable
I5-D2. Similar to REWERSE, the ECSS is subdivided into
participants, i.e., universities, working groups, and a central
node. Each node has its - locally administered - Web site. Events
that occur in this community include changes in the personal data
of members, keeping track of the inventory of the community owned
library, or simply announcing information from email newsletters to
interested working groups. These events require reactions such as
updates, deletion, alteration, or propagation of data, which are
implemented using XChange rules. The rules run locally at the
different Web nodes of the community, allowing for the processing
of local and remote events.
While a similar behavior could be obtained with conventional means of programming, XChange provides an elegant and easy way to arrange for evolution of data and reactivity on the Web using readable and intuitive ECA rules. Moreover, by employing and extending Xcerpt as a query language, XChange integrates reactivity to events, querying of Web resources, and updating those resources in a single language.
Contact: Michael Eckert
(Munich)
Prototype of a general ECA framework for the Web
The prototype of the "General ECA Framework" approach described
in I5-D4, Chapter 3, is under implementation towards I5-D4 (month
30). The current demo shows the state of the art of an
implementation of the central ECA functionality in combination with
a simple event detection service and XML databases. We will
illustrate the communication mechanisms and the execution semantics
by monitoring the execution of some sample rules.
Further information can be found at
http://www.dbis.informatik.uni-goettingen.de/eca/
Contact: José Júlio Alves Alferes (Lisbon), Wolfgang May (Göttingen)
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