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A DataSource corresponds to the datasource tag in GFD files. It defines 
a query or source.  It contains DataSets, but not actual data. 

A DataSet is a traversable set of RecordSets.  It has no GFD equivalent, 
although most of GFBlock's functionality may consist of calls to 
DataSets.

A RecordSet is a set of the fields contained in a record.  A RecordSet 
knows the current state of itself and all its fields. 

A DataSet holds RecordSets.

A DataSource may hold several DataSets (i.e., detail datasets 
in a master/detail relationship). A master RecordSet contains 
a reference to its detail DataSets. 

To commit all changes, you would first .post() all DataSets (recursively)
and then do a transactional .commit(). This method allows for multiple
detail sets to be maintained at once.

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DataSource: 
  getDataSet(): 
  
  addDetailDataSource() : Adds a DataSource in a master/detail relationship
  masterRecordChanged() : Called when master in master/detail is updated

  commit()      : 
  rollback()    : 


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DataSet: 
  |
  +-- DataSourceQuery extends DataSource
  |
  +-- DataSourceObject extends DataSource
  |
  +-- DataSourceSQL extends DataSource
  
  isFirstRecord() : Returns 1=At first record, 0=
  getRecord()   : returns 0=No records in memory, #=Current record #
  setRecord()   : move to record #, returns 1=New record loaded, 0=invalid #
  nextRecord()	: returns 1=New record loaded, 0=No more records
  prevRecord()  : returns 1=New record loaded, 0=At first record
  firstRecord() : returns 1=at first record, 0=No records loaded
  lastRecord()  : returns 1=at last record, 0=No records loaded
  deleteRecord():  
  insertRecord(): 
  isPending()   : Returns 1=DataSource has uncommitted changes 

  post()        : Post changes to the database

  current       : Link to current record (RecordSet)



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RecordSet:
  isPending()  : Returns 1=Record has uncommitted changes
  isDeleted()  : Returns 1=Record is pending a deletion
  isModified() : Returns 1=Record is pending an update
  isInserted() : Returns 1=Record is pending an insertion
  getField(f)         : Returns current value of "field"
  setField(f)         : Sets current value of "field"
  isFieldModified(f)  : Returns 1=Field has been modified
  getUpdateDict()     : Returns a dict containing field->changes
                        Will be used by the DBDriver to 
                        generate insert or update statements.
  dbIdentifier : Contains the identifier used by the DB drivers
  setDetailDataSet() : Sets the dataSet associated with this master record