code: public SPFPersona getPersonaOf(String appIdentifier) {
  		SQLiteDatabase db = mRegistryTable.getReadableDatabase();
  		String table = Contract.TABLE_NAME;
  		String[] columns = { Contract.COLUMN_PERSONA };
  		String selection = Contract.COLUMN_APP_IDENTIFIER + " = ? ";
  		String[] selectionArgs = { appIdentifier };
  		String groupBy = null;
  		String having = null;
  		String orderBy = null;
  		Cursor c = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
  		if (c.moveToNext()) {
  			String persona = c.getString(c.getColumnIndex(Contract.COLUMN_PERSONA));
  			return new SPFPersona(persona);
  		}
  
  		c.close();
  		return SPFPersona.DEFAULT;
  	}
docs: Returns the SPFPersona associated to the specified application. If the
  application does not exist returns the default SPFPersona.
  
  @param appIdentifier
  - the identifier of the application
  @return a SPFPersona