下面是Jena例子中的片段：
    public void 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 );
    }

为什么是先创建，然后再读取，那么保存在哪里？
例外文档中业没有说明更新或删除数据库中的本体应如何做

请各位指点一下，谢谢