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From Apache Wiki <>
Subject [Incubator Wiki] Update of "ClerezzaProposal" by RetoBachmannGmuer
Date Fri, 20 Nov 2009 07:50:42 GMT
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The "ClerezzaProposal" page has been changed by RetoBachmannGmuer.


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= Clerezza Proposal =
== Abstract ==
Clerezza is an OSGi-based modular application and set of components (bundles) for building
RESTFul Semantic Web applications and services.

== Proposal ==
Clerezza can be used as a platform providing all the compile and runtime requirement for building
such applications or used as individual bundles within e.g. Apache Sling, Apache ServiceMix,
or the Eclipse platform.

Clerezza provides:

 * An API modeling the W3C RDF standard without any vendor specific addition.
 * Adapter for various triple stores including Sesame, Jena TDB, and Mulgara.
 * Front-End adaptors, currently to run applications written against the Jena API. Support
for RDF2Go is planned.
 * A JAX-RS implementation designed to work in an OSGi environment and allowing to provide
Root-Resources as OSGi services.
 * Web access to RDF graphs, including a SPARQL-Endpoint.
 * Extensions to JAX-RS allowing to bind Root-Resource classes to specific RDF-Types rather
than to URI-Paths.
 * Templating mechanism (Renderlets) allowing to render RDF resources returned by JAX-RS resource
methods to various formats
 * Support for Scala for writing modules, ScalaServePages to easily write renderlets, DSL
for accessing graphs.
 * Authentication and authorization based on JAAS and OSGi Conditional Permission Admin
 * Support for user bundles: Users can have a permission to upload their own sandboxed bundles.
The URI space these bundles are allowed to register their JAX-RS resources can be limited
with a prefix.
 * Scripting: Scripting based on javax.script (currently support for JRuby and Scala)
 * Documentation: Bundles can provide their documentation in RDF. These are used for online
documentation as well as for building Maven sites (with a Maven reporting plugin)

The RDF abstraction layer can be used independently of other aspects of Clerezza. It allows
to write applications regardless the used backend. In its purpose, it is similar to RDF2Go,
but provides a significantly more modular interface allowing e.g. to independently switch
the storage, querying, or serialization layer. Furthermore, it doesn't introduce concepts
alien to the RDF model such as blank node labels, but is in its core strictly limited to RDF

The JAX-RS implementation can also be used independently of any other components. It allows
OSGi services to provide a REST-interface to their methods. By being based on wymiwyg WRHAPI,
it can run both on the default OSGi Web Service as well as on a jetty instance listening on
a different port.

== Background ==
The current web trends focusing on information sharing, interoperability and collaboration.
Therefore the behaviour of the end-user has changed over the last years: end-users not only
consuming information they also producing content anytime anywhere - in contrast to non-interactive
websites where users are limited to the passive viewing of information that is provided to
them. Since the end-users are sensitized to the possibilities of the web the web application
requirements increases. Examples of such applications are social-networking sites, wikis,
blogs and mashups.

The REST paradigm and Semantic Web technologies support these trends and form the basis for
the upcoming Web of Data (a.k.a. linked data, Web 3.0). They change the paradigms for developing
complex Web applications. Clerezza allows to develop applications that integrate perfectly
in the Semantic Web providing all accessible resources in machine understandable formats without
imposing additional burdens on the developer. Additionally, thanks to the flexibility of the
RDF model used as back-end, some tedious database related tasks required for traditional Web
application development are no longer needed.

== Rationale ==
Most Web application framework are not designed to leverage the full power of HTTP but often
try to reproduce non Web design patterns for the Web environment. In general, application
frameworks are oriented towards relational or hierarchical data structures. While attempts
to overcome this such as Drupal have become very popular, they do not at their core base on
the stack of Semantic Web standards. Clerezza will prove that the flexibility of the RDF doesn't
result in increased complexity, but on the contrary allows for fast prototyping and development.

== Initial Goals ==
The initial goals for Clerezza are:

 * Donate the existing codebase and import it.
 * Setup the incubation infrastructure (svn repository, build system, website), so we can
run continuous builds with automated tests and publish all available documentation.
 * Get people involved in advancing the code base in different directions, integrating it
with other projects at Apache.
 * Prepare for an initial release that demonstrates the systems core capabilities.

== Current Status ==
The current codebase is developed and tested using Apache Felix. It has been developed intensively
and reviewed at trialox since August 2008 using Scrum and having a development process emphasizing
individual accountability and reviews. We have internally demonstrated that we can release
codes as scheduled. Platform core functionalities are available, however the need of new features
may arise, performance and robustness could be improved. Incomplete documentation for the
project is available with the individual artifacts, both in the generated maven sites as in
a version available exposed by Clerezza at runtime we also have a wiki at [[|]]
with some information mainly on the development process. We also use mailing lists for communication
among developers and users.

=== Meritocracy ===
The core developers understand what it means to have a process based on meritocracy. We will
provide continuous efforts to build an environment that supports this, encouraging community
members to contribute.

=== Community ===
Trialox has been developing the current codebase since August 2008. Trialox was founded in
partnership with the University of Zurich and could profit from previous research work at
the Department of Informatics. Part of the team from the beginning was Reto Bachmann Gmür
who has been developing open source Semantic Web applications for many years, including working
with the Jena team at HP Labs.

Trialox has contributed to the JAX-RS specification. Some of the code written by trialox is
used by Open Source projects such Paxle and Gradino.

Clerreza is used by globally active non-profit organisations such as the WWF. These organisations
have strong developer networks including motivated volunteers, which will contribute to Clerezza.

=== Core Developers ===
People from Trialox, the University of Zurich, as well as partner companies of Trialox have
contributed to the project. Currently, the following persons are core developers of Clerezza:

 * Manuel Innerhofer, Developer at Trialox since November 2008.
 * Hasan Hasan, Developer and Senior Researcher at University of Zurich since 2006, developing
Clerezza since August 2008. His current research interests cover P2P networking, Service Level
management, and Internet security.
 * Tsuyoshi Ito, Developer and Scrum Master at Trialox, developing Clerezza since August 2008.
He has researched at the University of Zurich since 2005. His research interest was computer-supported
Learning (Educational Engineering)
 * Reto Bachmann-Gmür, Developer and Architect at Trialox, developing Clerezza since August

=== Alignment ===
We provide a launcher which runs Clerezza's bundles within Apache Felix. We also provide feedback
about the usage of Apache Felix and its components including the framework security via the
mailing list. For building Clerezza's bundles we use Apache Maven and various plugins. We
also have developed a plugin to help managing projects which contain ontologies, so that Java
classes representing those ontologies can be pre-compiled. Other projects which based on Web
services and/or RDF can benefit from Clerezza or its specific bundles. We are open to collaborate
with other Apache projects which can benefit from functionality provided by Clerezza. Clerezza
has the advantage of being very modular and independent of application frameworks, thus can
be easily integrated with other Apache projects. UIMA and Tika come to mind, as they would
help extract semantic information from various data types and formats. An alignment to the
JAX-RS implementation in Apache CXF could not only help removing the dependencies to the CDDL
files taken from Jersey but also help providing a fully framework independent implementation
with a larger group of developers and thus higher quality.

== Known Risks ==
The current size of Clerezza core developers is small, but by innovative project in the semantic
"space", we are confident that new developers will join and commit.

 . Clerezza has been started as an Open Source project providing mercurial repository for
public access to source codes and also a publicly accessible JIRA instance for issues tracking.
Clerezza is licensed since project begin under Apache License version 2.0. Some of the initial
committers already have strong experiences with Open Source software development. Others,
while not being totally inexperience, are willing to learn.

The risk that Clerezza will be an orphaned product is considered small. Three main factors
will avoid this to happen:

 * Trialox and its founder Getunik have a vital interest in continuos development in this
open source foundation
 * Clerezza is used as foundation for research as well a student projects at the University
of Zurich
 * There is a strong commitment by Reto Bachmann-Gmür to maintain Clerezza
 * WWF expressed their support to deploy Clerezza

== Documentation ==
A small set of further documentation is available under the following links:

 . [[|1]] [[|2]]

== Initial Source ==
Clerezza has been in development since mid 2008. Public access to the source is provided through

== Source and Intellectual Property Submission Plan ==
The current codebase is owned by trialox, and will be donated together with its documentation.
We will get the paperwork out of the way as soon as possible.

== External Dependencies ==
There are quite a few open source libraries already used. However, they have Apache compatible
licenses. The libraries, their sources and licenses are listed here:

Apache Felix, ASL:

 * Framework
 * Framework Security
 * Configuration Admin
 * maven-scr-plugin
 * maven-bundle-plugin

OSGi Alliance, ASL:

 * Core
 * Compendium

Apache Maven, ASL:

 * apache-maven

Eclipse, ASL:

 * Jetty


 * Pax Exam


 * wrhapi
 * wymiwyg-commons

jQuery, MIT license:

 * jquery

Hewlett-Packard Development Company, BSD License:

 * Jena, BSD license:

 * Sesame, Open Software License ("OSL") v. 3.0:

 * mulgara

XSite (, BSD license:

 * xsite-maven-plugin

Jersey (, CDDL license

The current code bases on code licensed under the CDDL, we understand we have to get rid of
these before making a release. The following files are affected.


== Required Resources ==
Mailing lists:

 * clerezza-dev
 * clerezza-commits
 * clerezza-user (only after leaving the incubator)



Issue Tracking:

 * JIRA: Apache Clerezza (Clerezza)

== Initial Committers ==
These committers have either worked on the initial codebase (Reto, Immanuel, Tsuy, Hasan)
or expressed an interest in extending the project:

 * Reto Bachmann-Gmür
 * Manuel Innerhofen
 * Tsuyoshi Ito
 * Hasan Hasan
 * Bertrand Delacretaz
 * Michael Marth

== Affiliations ==
Manuel Innerhofen, Tsuyoshi Ito and Reto Bachmann-Gmür work at trialox and might get paid
to do certain work on Clerezza.

 . Hasan Hasan from University of Zurich is paid to work in a project that bases on Clerezza.
Michael Marth and Bertrand Delacretaz work for Day Software.

== Sponsors ==
We have approached both the champion and an initial list of mentors that have agreed to mentor
this project.


 * Bertrand Delacretaz


 * We are looking for mentors


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