没有发现有xmlns前缀和xml:base，怎么回事啊，请大侠们指教。多谢！
代码太长,主要是在程序中自动产生一个OntModel,并保存到数据库中,涉及到NsPrefix仅有以下代码片段:
ModelMaker maker = po.getRDBMaker(SharingVar.DB_URL, SharingVar.DB_USER,
                                      SharingVar.DB_PASSWD, SharingVar.DB, false);
    OntModel owlmodel = po.loadDB(maker, s_source);
    owlmodel.setNsPrefix("base", s_source);

其中s_source ="http://www.edu.cn/jianyankm#"

//*************************
public OntModel loadDB( ModelMaker maker, String source ) {
      // use the model maker to get the base model as a persistent model
      // strict=false, so we get an existing model by that name if it exists
      // or create a new one
      Model base = maker.createModel( source, false );

      // now we plug that base model into an ontology model that also uses
      // the given model maker to create storage for imported models
      OntModel m = ModelFactory.createOntologyModel( getModelSpec( maker ), base );

      // now load the source document, which will also load any imports
      //m.read( source );
      return m;
  }
//****************************************************
public ModelMaker getRDBMaker( String dbURL, String dbUser, String dbPw, String dbType, boolean cleanDB ) {
      try {
          // Create database connection
          IDBConnection conn  = new DBConnection( dbURL, dbUser, dbPw, dbType );
          Connection heicon = conn.getConnection();
          heicon.setAutoCommit(true);

          IRDBDriver mydriver =conn.getDriver();

          //conn.setAutoCommit(false);
          // do we need to clean the database?
          if (cleanDB) {
              //DriverRDB.unlockDB();
               //mydriver.unlockDB();
              conn.cleanDB();
          }

          // Create a model maker object
          return ModelFactory.createModelRDBMaker( conn );
      }
      catch (Exception e) {
          e.printStackTrace();
          System.exit( 1 );
      }

      return null;
  }

另外xmlns:base我觉得只是简单的定义了一个叫base的名字空间，和前面两个概念没有任何联系

write
Model write(java.io.OutputStream out,
            java.lang.String lang,
            java.lang.String base)Write a serialized represention of a model in a specified language.

The language in which to write the model is specified by the lang argument. Predefined values are "RDF/XML", "RDF/XML-ABBREV", "N-TRIPLE" and "N3". The default value, represented by null, is "RDF/XML".

Parameters:
out - The output stream to which the RDF is written
base - The base uri to use when writing relative URI's. null means use only absolute URI's.
lang - The language in which the RDF should be written
Returns:
This model