Hi Amirouche,

On Mon, Jul 20, 2020 at 2:01 AM Amirouche Boubekki <
[email protected]> wrote:

> Le lun. 20 juil. 2020 à 03:57, Lansana Camara <[email protected]> a écrit
> :
> >
> > Can you provide a diagram of the architecture?
>
> A DHT backend could be used to spread the on-disk load over many
> peers, but only as _cold storage_ not as a primary source of truth.
>

Um, no, I am unclear on why you are making a distinction between hot and
cold storage. The current three prototypes all provide hot storage, and
have no provisions at all for cold storage.


> > I'm having a hard time visualizing high-performance servers being wired
> up by a database.
>
> I am not sure I understand that. Every system requires some kind of
> database.


The atomspace is a database. It is an in-RAM database.


> What could be done is to have a Single Source of Truth


There is no single source or truth.  Fundamentally, there cannot be. Some
people will say "eventually consistent", but I am not aware of any reason
why that is desirable. Yes, I understand that certain kinds of datasets
might need to be consistent, but this should NOT be a built-in property of
the database!

This is a VERY IMPORTANT point that results in a huge amount of friction
and confusion because it leads people into making utterly terrible design
decisions that have no rational basis.  I have worked very long and very
hard to completely eliminate all concepts of "eventual consistency" and
"single source of truth" from the atomspace.  These are two of its
important selling-points! Don't erase or subvert them!

where
> everything is persisted forever


No, not forever. Deletion IS a very important quality!

and secondary sources of truth where
> expert systems (high-performance services) store the data in their
> favorite schema.


You've lost me. That atomspace is a database. It has a certain built-in
schema that is (supposed to be) general enough to layer other schemas on
top. The idea is that any "favorite schema" can be easily/trivially layered
on top of the atomspace. This is "mostly true" today, but there remain some
ugly bits that I would like to see fixed.

This is usually the case of Event Sourcing systems.
> The whole system is eventually consistent.


Again, No. This is NOT a desirable property of the system!  It's an
anti-pattern.

That means that a given
> expert system will have to wait sometime before they become aware of
> new knowledge. The advantage is that you keep around all the data in
> the log, the event source,


That is what the demo at  https://github.com/opencog/atomspace-cog/ is. It
is the "event source"


> and aggregate the useful knowledge for a
> given system in a fine-tuned highly performant database for specific
> uses.


That is what the atomspace is. It is a fine-tuned, high-performant
database. It's got the highest performance possible, that I have been able
to squeeze out of it, and if someone thinks they know how to make it
faster, ... well, that would be a very interesting direction to go in. But,
to get faster, it would need some truly new, radically different approach,
and I cannot really imagine what that would be.

This is not my favorite approach but it is workable.
>

:-/

--linas

-- 
Verbogeny is one of the pleasurettes of a creatific thinkerizer.
        --Peter da Silva

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