Data Objects
Data Objects package together a program (the translator or
method) and data. User programs never look at the data directly;
rather, they communicate with the data object
Data Objects communicate with a common protocol
- All data objects present the same appearance to outside
(described here)
- Programs can work with any data in
the system (Example)
Data Objects handle
Projection (subsetting by variable name)
Selection (subsetting by variable values)
- Can minimize transmission of data
- Individual objects may have other functions