Contact Point:

Aggeliki Dimitriou ( )

National Technical University, Athens
  

Technical Contact Point:

Aggeliki Dimitriou ( )
  

Type of Software:

PROTOTYPE
   

Descriptive Keywords:

peer-to-peer, digital library, query reformulation, mappings
   

Potential Use and Applications:

Dynamic networks of DL systems
  

General Description:

Our prototype supports data management in a dynamic network of autonomously managed digital library nodes. Autonomy in this context refers to the following objectives:

Joining and leaving the library. Each DL node chooses itself when to join and/or leave the library network. The system can gracefully adapt to these joins and departures without any global structural knowledge.

Data management. A DL node is responsible for managing its own local data, as well as maintaining information (expressed as schema mappings) about data residing at other peers. Every DL node in our system should store data organized in the RDFS model. However, there are no restrictions on content representation nor any global schema information, i.e., a DL node may use its own RDFS representation.

Query processing. Queries can be issued at any DL node and propagated to other DL nodes in its neighbourhood (and so on). A query, prior to its propagation to other DL nodes, is reformulated using schema mappings in order to match schema information at the remote DL nodes.

For more information: http://milos.dblab.ece.ntua.gr/p2pdl/
  

Technical Description:

Our prototype has been built on top of the JXTA PP software (http://www.jxta.orgrg). The DL network is organized in JXTA groups. At least one DL node in each group provides the necessary scope to message propagation. Every such DL node maintains JXTA advertisements for schema information and mapping information.

Our system implements the following facilities:

Setup. After its creation, every new DL node makes its schema advertisement (with its RDFS schema primitives) public to any other DL node.

Joining the network. To join the network, a DL node obtains the list of available DL nodes that participate in the network. Then, the DL node's admininstrator (using a mapping wizard) selects some of those DL nodes (i.e., its neighborhood) and determine the mappings between those nodes and the new DL node. Mappings are stored in the mapping advertisements of the new DL node.

Querying. Queries can be issued at any DL node and propagated to other DL nodes in its neighbourhood (and so on). Query reformulation is assisted using a query wizard. In each DL node, we provide a Sesame RDF query engine (http://www.openrdf.org/). Every query formulated using the wizard is transformed to a Sesame RDF query to be executed on the RDF data. A query, prior to its propagation to other DL nodes, is reformulated by renaming its RDFS properties according to the mappings defined in the mapping advertisement, in order to match schema information at the remote DL nodes.

For more information: http://milos.dblab.ece.ntua.gr/p2pdl/
  

Required User Skills:

No special skills needed.
  

Pre-Requisites for Installation:

JDK 1.4.2, JXTA 2.3.1, Sesame 1.2.6
  

Conditions of use:

Free downloading. For instructions please refer to http://milos.dblab.ece.ntua.gr/p2pdl/