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From: Reinhold Klapsing <Reinhold.Klapsing@uni-essen.de>
Date: Tue, 28 Dec 1999 16:22:49 +0100
Message-ID: <3868D5C9.6A51043C@uni-essen.de>
To: www-rdf-interest@w3.org

Dan Brickley encouraged me to introduce the XWMF project [1] and the
corresponding tools.

By means of the XWMF (eXtensible Web Modeling Framework) project we
want to evaluate the suitability of RDF as a basis for modeling web
based information systems. XWMF is based on the Resource Description
Framework (RDF). Both frameworks, RDF and XWMF use metadata to
describe properties of web resources. Our proposed framework applies
the same (meta-) data model to specify the structure and the content
of a web site and to make statements about the elements of a web
site. A formal model defining the various properties can lead to a
consistent structure and easier maintenance. As RDF is the basis, a
XWMF model results in machine-understandable and inter-operable
content- and meta-data of a web site. The data model is capable to
define the structure of information from small units such as elements
or single web pages (for authoring-in-the-small) to large structures
such as web sites (for authoring-in-the-large). The formal model of
XWMF can lead to the development of better software tools supporting
web site development and maintenance. Outcomes of the XWMF project we
want to present are the XWMF tools (a collection of XOTcl [2] and Tcl
programs for processing RDF data) and the GraMToR (a graphical RDF
editor). The scripts for modeling and constructing a web-site are
currently not included. The XWMF tools are available as
open source. See [1] for detailed copyright information. The programs
are developed and tested with various distributions (Red Hat and Suse)
of Linux.


The XWMF tools [3] consists of several parts.

- rdf_parser

  An RDF parser for processing RDF data models according to the RDF
  Model and Syntax Specification [4]. Currently not all RDF constructs
  can be processed. The rdf_parser is a modified version of the xoRDF-
  Version 0.9 (beta) an XOTcl based RDF parsing system written by
  Gustaf Neumann and Uwe Zdun. xoRDF is also available on [5]. For
  examples of how to use the rdf_parser see the scripts in the
  directory rdf_parser/tests.

- rdf_handle

  A tool for processing and querying RDF data models written by
  Alexander Block and Reinhold Klapsing. The results (RDF triples)
  generated by the rdf_parser can be read by the rdf_handle. It is
  able to store the data of RDF data models in a suitable way and
  builds up a base for further processing of this data. One of the
  features of the rdf_handle is a query language similar to SQL. By
  means of the rdf_handle query language it is possible to query the
  triples of an RDF data model using a query string. The result is a
  subset of triples fulfilling a query. In the following the structure
  of the query string is presented in an informal manner (for a formal
  description see the grammar [6] of the query language):

  SELECT   subject,predicate,object,parsetype
  FROM     <triples of a certain RDF data model>
  WHERE    subject | predicate | object | parsetype = "<value>"
  AND | OR subject | predicate | object | parsetype = "<value>"
  ORDER BY subject | predicate | object | parsetype

  The triples given with <triples of a certain RDF data model> build a
  list of statements such as {predicate,[subject],[object]} and/or
  {predicate,[subject],"object"}. <value> represents the content of a
  part of a statement that should be filtered with the query.

  For examples of how to use the rdf_handle see the scripts in the
  directory rdf_handle/tests

  The source code of the rdf_handle is commented in English; however,
  documentation concerning the source code is not available. For a
  better understanding of the relationships between the XOTcl classes,
  you may take a look at the class diagram [7] of the rdf_handle. The
  grammar of the SQL-like query language implemented by the rdf_handle
  is written in a form similar to the Extended Backus Naur Form (EBNF)
  and can also be downloaded [8]. In addition, there is a component
  diagram [9] showing the relationships of the different files of the

- library

  (XO)Tcl-Scripts which are useful for more convenient programming.

- packages

  This directory contains the TclXML parser (Version 1.1.1) written by
  Steve Ball. The TclXML parser is also available at [10].

Requirements for installation:

  - XOTcl (version 0.76 or higher). XOTcl (XOTcl, pronounced
    exotickle) is an object-oriented scripting language based on MIT's
    OTcl. For more information about XOTcl see [2]

  - TCL version 8.0 or higher which is available at the scriptics home
    page [11].



is a graphical editor for interactive constructing an RDF data
model. The graphical representation can be serialized to XML-RDF
syntax. Additionally the data model can be serialized in the triple
notation. GraMToR is able to store an RDF data model in one of three
kinds: Files with the extension

 - .rdf contain XML-RDF syntax. 
 - .fmr contain triple notation. 
 - .brm contain triple notation with additional position information
   for the corresponding graphical RDF representation.

Documentation of the class system (german language) [12] and a user
guide (german language) [13] is available. The GraMToR is a first
prototype with which we gained experience in graphical processing of
RDF data models. The program logic of the underlying processing model
should be replaced with a more sophisticated model.  Currently, our
main focus is on the development of the XWMF tools to provide a more
sophisticated model.

Requirements for installation:

 - Wafe (version 1.0.20 or higher). Wafe (Widget[Athena]front end) is
   a package that implements a symbolic, string based interface based on
   Tcl to the X Toolkit, the Athena Widget Set (or the three-D version 
   of the Athena Widget Set Xaw3d), the OSF/Motif Widget Set (versions
   1.1 to 2.0) and various complementary widget classes and extension
   packages. For further information about Wafe see [14].
 - TCL version 8.0 or higher which is available at the scriptics home
   page [11].

Further Readings 

- XWMF poster abstract (published at the WWW8) available at

- Results (german language) of a course held in summer 1999. 
  Course theme: Development of applications for processing RDF-models.

- Results (german language) of a course held in winter 1998. 
  Course theme: Modeling of web-sites by means of meta-data (RDF). 


For questions, criticisms, hints, improvements, patches, etc. please
contact Reinhold Klapsing. Email: Reinhold.Klapsing@uni-essen.de



Received on Tuesday, 28 December 1999 10:22:38 UTC

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