Apache Clerezza

Clone this repo:
  1. 924e6d8 CLEREZZA-1047: Fix configuration of maven-remote-resources-plugin in parent/pom.xml and use version 21 of org.apache.apache by Hasan · 12 days ago master
  2. ebcd164 CLEREZZA-1048: Add public code signing key of hasan@apache.org to file KEYS by Hasan · 12 days ago
  3. 36ee89b Add header information about usage in the file KEYS by Hasan · 9 weeks ago
  4. 8576350 CLEREZZA-1045: Add empty relativePath to resolve the parent POM from the repositories by Hasan · 3 months ago
  5. 0671846 CLEREZZA-1044: Remove deprecated SimpleMGraph by Hasan · 3 months ago


Build using Apache Maven with

mvn install


Some more advanced questions focused on showing the differences to other proposed APIs.

Can I add RdfTerms from one implementation to another?

Yes, any compliant implementation of BlankNode, Iri or Literal as well as Triple can be added to any implemenation of Graph, as long the Graph supports adding triples. Implementation may not require the nodes to be of a particular implementation of having been created with a specific factory.

How does it work?

Implementation might need to map instances of BlankNode to their internal implementation. This should be done in a way that when there is no more reference to the BlankNode object (i.e. when the object can be garbage collected) the mapping to the internal implementation is removed from memory to. This can be achieved by using a java.util.WeakHashMap

Do I get back the same object that I added?

For instances of Iri or Literals you get back an object that result equal to the originally added object, i.e. an object with the same HashCode and of which the equals method return true when compared with the originally added object. Ther is no guarantee that the same instance will be returned. For instances of BlankNode the above in only guaranteed as long as the original object is referenced. When the original object becomes eligible for garbage collection the implementation may start returning a different (an not equal) object. In practice this means BlankNode objects cannot safely be serialized (using Java serialization) or passed around via RMI.

Can an implementation remove redundant information from a Graph?

Yes, as long as this doesn't affect any BlankNode instance that is currently reachable (i.e. the Java object is in memory and is not eligible for garbage collection).

For example given the non-lean graph:

ex:a ex:p _:x .
_:y ex:p _:x .

As long as there is no BlankNode instance referencing _:y the implementation can reduce the graph to:

ex:a ex:p _:x .

removing the redundancy. If however there is a reachable BlankNode instance for _:y the implementation must not remove the redundancy as the code which has access to the object can go on adding a triple:

_:y ex:p2 ex:b .

Thus creating a graph that doesn't contain any internal redundancy, namely:

ex:a ex:p _:x .
_:y ex:p _:x .
_:y ex:p2 ex:b .