Data Management

DDMS Overview


Basic Elements

Data Objects


User Applications

Manipulating Data


Further Info

Data Management

Detailed Information About the JGOFS Distributed Database Management System (DDMS)

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



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