[kwon-young]

The article mentions prolog but doesn't mention you can use constraints to fully express his computation graph. My prefered library is clpBNR which has powerful constraints over boolean, integers and floats:

  Welcome to SWI-Prolog (threaded, 64 bits, version 9.2.9)

  ?- use_module(library(clpBNR)).
  % *** clpBNR v0.12.2 ***.
  true.
  
  ?- {TotalOwed == TotalTax - TotalPayments}.
  TotalOwed::real(-1.0Inf, 1.0Inf),
  TotalTax::real(-1.0Inf, 1.0Inf),
  TotalPayments::real(-1.0Inf, 1.0Inf).
  
  ?- {TotalOwed == TotalTax - TotalPayments}, TotalTax = 10, TotalPayments = 5.
  TotalOwed = TotalPayments, TotalPayments = 5,
  TotalTax = 10.

If you restrict yourself to the pure subset of prolog, you can even express complicated computation involving conditions or recusions. However, this means that your graph is now encoded into the prolog code itself, which is harder to manipulate, but still fully manipulable in prolog itself.

But the author talks about xml as an interchange format which is indeed better than prolog code...

[alexpetros]

In the blog I link to a Prolog post I wrote in January because I am very interested in the possibility of using Prolog to prove things about the Fact Graph. I have a personal branch where I try to build some tools for it with DCGs. The nice thing about XML is that I can easily explore it as Prolog terms with committing the entire project to Prolog.