Using references instead of nesting

Please describe a summary of the new feature (in a paragraph):

In some cases, reference-based relation description is useful for reducing the 
abundant spaces 
for representing nested structured data. For example, consider a silk data with 
a nested 
structure:

-track group
 -track
  -name: track A
  -property:
    -left margin: 100
 -track
  -name: track B
  -property:
    -left margin: 100
 -track
  -name: track C
  -property:
    -left margin: 100

Another way to describe the same meaning data is:

-track group(id: 1) 

-track
 -track group(id:1)
 -name: track A
 -property:
  -left margin: 100
-track 
 -track group(id:1)
 -name: track B
 -property:
  -left margin: 100
-track 
 -track group(id:1)
 -name: track C
 -property:
  -left margin: 100

Please provide any additional information below:

Original issue reported on code.google.com by taroleo on 22 Apr 2010 at 3:05

AnantLabs / xerial

Using references instead of nesting #67