PLUGINS

                           Sonar 1.0.0
                       Plugin Architecture

Sonar offers a simple extension mechanism that can be used to write
custom centrlity algorithms. Centralities can be reloaded during a
servlet refresh and will be made available automatically for the
frontend. If you do not know what a centrality is use the search
engine of your choice to find out.

                      Stability:   Unstable
                     API version:  0

0. Prequisites
-------------------
  You either need to obtain the Sonar source code and
use build your centrality with war/WEB-INF/classes in your classpath
or you just download the centrality API library which is usually
shipped as a single jar (sonar.centralities.api-1.0.0-rc1.jar).
  You can write a centrality in any language supported by the Java
Virtual Machine (JVM) but you have to make sure that you deploy
your runtime properly. This can be done by copying the runtime into
the WEB-INF/lib directory.

1. Implementation
-------------------
  Every centrality needs to implement the
edu.kit.ipd.sonar.server.centrality.CentralityImpl class. It has
to implement all abstract methods, in particular getType(), getWeight,
getVersion, getName, getRequiredAPIVersion.

1.1 Required API
-------------------
  Version If you require a special API version of
Sonar check the current API version as provided in the docs or this
document. If you do not require any special API version you should
use the value 0.

1.2 Type
-------------------
  A centrality can either calculate weights on nodes or
edges. If your centrality plugin operates on Nodes you have to
return Centrality.NodeCentrality from getType. Similar you have to
return Centrality.EdgeCentrality if your plugin operates on edges.
Note that it is not supported that a centrality handles both nodes
and edges.

1.3 Name
-------------------
  The name of the centrality should be returned by getName.
E.g. "Outdegree (Scala)"

1.4 Version
-------------------
  Centrality plugins should return a simple integer as
it's version. The plugin system assumes that two centralities with
the same version and name are equal.  Hence increment your version
number on every release of your centrality.

1.5 Calculations
-------------------
  Please refer to the Javadoc of CentralityImpl.getWeight
for further information about the exepcted return value.

2. Deployment
-------------------
  To deploy your centrality. Put it into the WEB-INF/lib
directory and add the full qualified name of the classes to
WEB-INF/classes/plugins.config. Reload your servlet container.

Make sure you that all required runtimes and libraries are also
copied to the WEB-INF/lib directory.

Note: The deployment strategy is most likely to change before 1.0.0
final.

3. Stability
-------------------
  The Sonar plugin architecture is marked with a stability
level. The following stability levels help you to understand the
current stability of the plugin API and the deployment mechanism.

    Unstable:    The API interface and deployment strategy can
                 change. There is no API compatibility.

    Evolving:    The API interface will most likely not changed but
                 deployment mechanism might change.

    Stable:      The API interface for the given API version will
                 not change anymore. Deployment mechanism are
                 supported and will be supported by further versions
                 of Sonar.

    Deprecated:  The support for this interface and deployment
                 mechanism will not be supported in future major
                 releases, but will be supported in minor releases.

    Unsupported: Not longer supported.

4. License
-------------------
  The plugin mechanism of Sonar is licensed under the GNU
Lesser General Public License version 2.1 of the license.