About schemes

An ORD is a list of one or more queries separated by the “│” pipe symbol. Each query is an ASCII string formatted as “<scheme>:<body>”.

Figure 21. Example ORD scheme and body

scheme

The scheme name is a globally unique identifier which specifies, in Niagara, how to find a piece of code to lookup an object from the body string. Refer to Types of schemes for a listing of different types of schemes.
body

The body string is formatted differently, according to the requirements of the scheme. The only rule is that it cannot contain a pipe symbol. Queries can be piped together to let each scheme focus on how to lookup a specific type of object. In general, absolute ords are in the following format: host │ session │ space (see Figure 20).

Some examples follow:
- ip:somehost│fox:│file:/dir/somefile.txt
  
  In this example, the “ip” scheme is used to identify a host machine. The “fox” scheme specifies a session to that machine usually on a specific IP port number. Finally, the “file” scheme identifies an instance of a file within the “somehost” file system.
- ip:somehost│fox:1912│station:│slot:/Graphics/Home
  
  In this example, the “ip” scheme is used to identify a host machine using an IP address. The “fox” scheme specifies a session to that machine usually on a specific IP port number. Finally, the “station” and “slot” schemes identify a specific component in the station database.
- local:│module://icons/x16/cut.png
  
  This example illustrates a special case. The scheme “local” which always resolves to BLocalHost.INSTANCE is both a host scheme and a session scheme. It represents objects found within the local VM.