Well, from what I've read GIMP 2.10 will not be released until all native filters are ported to GEGL. From what I've seen in GIMP 2.9, remains a long way to reach that goal.
http://wiki.gimp.org/wiki/Hacking:Porti ... rs_to_GEGL
http://wiki.gimp.org/wiki/Hacking:Porti ... GL_and_GIO
http://gegl.org/index.html

I know nothing about programming. I know that in this forum there are very good scripts and plug-ins developers. I would like to know if you can explain me in simple words what you think/know about GEGL. What advantages does GEGL? How easy is to program filters in GEGL compared with current methods? Could GEGL make easier the creation of new filters to those who have no idea of programming?

See http://en.wikipedia.org/wiki/GEGL

One advantage of GEGL is that it eventually lets Gimp describe internally the processing as a sequence of operations, so you can do non-destructive editing. A canonical example of the benefits is that when you apply several effects on text, you can still edit the original text and the effects will all be applied on the fly on the new text.

I haven't got the answer to the other questions, but programming is... programming. What is difficult is acquiring the mindset, the technique (Scheme, Python or some hypothetical GEGL node editor) is anecdotal.

At GEGL site under Documentation have a look through the Operations. Many of the opening explanations are useful.

Here's a few more links,
Gimp Help 8.5. Use GEGL and 6.7. GEGL Operation
Gimp developer faq GEGL 4.3
GEGL explained
Making GEGL useful for applications beyond GIMP

Thank you all for the explanations and links.
I understand some things. I do not understand much other related to technical programming terminology.
That about "operations" and "nodes" I do not know if I understand correctly. That means we could eventually have a graphical interface for creating filters based on nodes?
Also "operations" sounds me like procedures that can be stored neatly and then be repeated. It could GEGL facilitating add natively the feature of recording actions to be repeated later in batch? I read that record actions is a very requested feature by PhotoShop users.

Just a few minor corrections, if you don't mind.

1) Filters don't absolutely have to be become GEGL operations all at once, but it would be nice.

2) OpenEXR and RGBE support is not a possibility, it's a reality by now, albeit in an unreleased state. Also, the OpenEXR plugin is very simplistic and doesn't yet provide any user-configurable settings for opening/exporting.

3) It's OpenCL rather than OpenGL, but the outcome is the same: GPU-side rendering and processing. Multithreading was experimentally added this summer as well.

4) There is no final UI decision made on how non-destructive editing would be implemented, exactly. GIMP might provide direct access to editing the graph or it might not. This is simply undecided, as there are more pressing matters currently.

5) Automating GIMP will eventually become simpler thanks to GEGL indeed, although, with a tree of nodes, there doesn't necessarily have to be a record button

Appreciate the update. Indeed, there is no need for actions if you have nodes.