| Previous | Table of Contents | Next |
The DAF describes a generic interface for navigating and reading data from complex data structures including relations between
objects. Both DAF and DAIS support navigation in a space of hierarchically structured objects (an object is called a node
in DAIS and a resource in DAF). Both support identification of objects and properties at an object. In DAIS an instance of
property at an object is called an item and an ItemID (item identifier) identifies an item. An ItemID consists of a ResourceID
(resource identifier) for the node and a PropertyID (property identifier) for the property. The DAIS API uses ItemIDs to access
data while the DAF uses ResourceIDs and PropertyIDs separated.
A system may implement both a DAF server and a DAIS server. In such a system it shall be assumed that the same object will
have the same ResourceID seen through either API. This means it shall be possible to navigate to an object, retrieve its ResourceID
through one of the APIs, and use that ResourceID with the other API. In the same way PropertyIDs are the same.
Textual identification of resources and properties in the DAF is by URIs (Uniform Resource Identifier). ResourceIDs and PropertyIDs
have their own URIs. URIs can be translated into corresponding ResourceIDs and PropertyIDs and vice versa. A property name
is a URI where the container part is a unique schema identifier and the fragment part is the property name.
For example:
http://www.epri.com/schema/CIM-07f.xml#Measurement.positiveFlowIn
DAIS does not support URIs directly but has a textual representation for nodes, items, types, and properties. This textual
representation may correspond to the fragment part of a URI.