An Explicitly Relational Neural Network Architecture | Hacker News Reader

An Explicitly Relational Neural Network Architecture

arxiv.org

83 pointsjonbaer26 comments

i'm not familiar with the standards of reproducibility in computer science, but compared to many other disciplines, it should be trivial to release "research-quality" [+] source code or a vm/container image that allows others to more directly attempt to reproduce the results described in the paper.

This paper's section on related work calls out a recent paper by Asai

> Asai [1], whose paper was published while the present work was in progress, describes an architecture with some similarities to the PrediNet, but also some notable differences. For example, Asai’s architecture assumes an input representation in symbolic form where the objects have already been segmented. By contrast, in the present architecture, the input CNN and the PrediNet’s dot-product attention mechanism together learn what constitutes an object.

re: [1], Asai's paper: https://arxiv.org/abs/1902.08093 .

Asai has released code for earlier papers on github: "LatPlan : A domain-independent, image-based classical planner". https://github.com/guicho271828/latplan

it reads as if the code for [1] may be open-sourced in future "Asai, M.: 2019. Unsupervised Grounding of Plannable First-Order Logic Representation from Images (code not yet available) "

[+] research-quality, i.e., in whatever random state the prototype code it happens to be in, without any guarantees about it compiling, or running, or behaving correctly, having an automated test suite, or whatever. in all of these cases, it is _technically_ trivial to make it available to the wider research community

This is from DeepMind. They rarely release source code at the time that the paper is submitted/published. They often release source code later on. While not ideal it seems like a billion times better than the situation where they don't publish at all. I don't think any of their results are fake so if nothing else it's a signal that says "this is possible to do in a way roughly described within".

Did they ever release sourcecode at DeepMind? I mean, not the frameworks or such but the code used for the experiments...

Tangentially, I have a concern with neural-symbolic hybrids, surely someone can address it. Do you think that symbols produced by a neural network (in a complex enough task) will ever be comprehensible by a human? Because my intuition here is that the symbols will look super complex and even random, and actually they will be just a combination that "just works" but we won't know why, just as other deep learnng models. Instead of arbitrary floats (weights), we will have arbitrary chains of symbols.

You might enjoy https://distill.pub/2018/building-blocks/. I’m on the ml interpretability team at OpenAI. Happy to answer any questions you have!

It looks super interesting, thanks! If I have any questions I'll let you know ;)

(By the way, probably you have the coolest job on earth)

It depends how those symbols are encoded. Techniques like attention, and systems like transformers that are built on top of them, are often produce highly interpretable execution traces simply because their patterns of activity are very revealing of how they are going about solving the task. It's harder to interrogate their learned weights in any free-standing way, of course.

But the neuro-symbolic concept learning paper I gave already shows the potential translucency of these kinds of hybrid systems: the linguistic interface (its a VQA task) allows one to simply look up the feature vectors and programs associated with particular phrases or English nouns. Similarly, the scene is parsed in an explicitly interpretable way, with bounding boxes for the various objects on which reasoning will commence. This 'bridge' theme between natural language and the underlying task space is really powerful, and it probably makes sense to figure out how we include them for systems that have nothing to do with natural language.

https://arxiv.org/abs/1901.11390 contains another great example of how interpretable such models can be, especially if they are generative. Take a look at those segmentations!

Lastly, https://arxiv.org/abs/1604.00289 lays out this vision in a lot more detail.

Many thanks for your answer!

Think of it like discovering a new human language. We use logic along with knowledge about the world to triangulate words that deal with concepts.

ML models work in the same way. Difference is they aren't human so it's harder to just use your empathy muscles (though even humans cut off from the rest of the world can come to pretty wild perspectives and ways of thinking). But they are logical, in some respect, and they are modeling our human perspective on some process in the world. But as a sibling comment posted in a link to the Distill paper, we need a lot of tools to make that process easier.

For example, very often researchers will probe single neurons and find they do something we find conceptually understandable, like a neuron detecting when you're inside a parenthetical when generating text so that the parenthesis is eventually closed. I'd expect the "symbols" to be very similar, because after all the neurons are symbols too. Both require you to either relate it to a small concept or put some together to create bigger concepts (or both).

Thanks!

That's a good point that is not often discussed. I've actually done some work into this kind of problem- how to explain automatically defined predicates in symbolic, logic-based machine learning:

https://github.com/stassa/metasplain

So that's "metasplain" a little program that explains "invented predicates", which is what I say above, predicates that are automatically constructed by a symbolic machine learning system in the process of learning. Think of them as invented features that are relevant to the learning task. These are given automatic names so they're difficult to read, especially if you have lots of them. Metasplain starts by automatically assigning meaningful names to invented predicates by combining the (not invented) symbols of their literals, then asks the user for improved names. It can go all the way automatically, without interaction, but the results are a bit meh. With a human in the loop you get the best of both worlds.

And that's what I think is the best way to solve interpretability problems in machine learning: instead of automating them, which is like trying to create a chicken so you can get an egg so you can hatch a chicken, put the human back in the loop and make it easy for her to provide meaningful explanations, even if she's not an expert.

Thanks, this direction looks promising and makes a lot of sense.

This looks very interesting. From my layman understanding they use very abstract input images (like tetris objects) in order to train the network to detect first-order logic statements. This demonstrates that a network might be one day fully restricted to utilizing strict logic internally, and thereby making it more auditable, efficient and generalizable.

Well that's very interesting work and it could potentially be very useful to my own reserach which is basically machine learning from symbolic representations. Unfortunately, from my quick readig of the paper it doesn't seem like the "relational" representations learned by PrediNet are ever encoded in explicitly symbolic structure, or that it is even possible to disentangle them from the trained model at all.

That would have been really useful, because for instance one could set up a pipeline with PrediNet on one end and the symbolic machine learning system I work with, Metagol [1], on the other end. That would be damn close to an ideal of a deep neural net as a "perceptual" unit and a symbolic machine learning system as a "reasoning" unit, which has long seemed to me like a winning combination, even the next big thing in machine learning- if anyone ever manages to get it right. Unfortunately, it doesn't seem PrediNet can be used in this way. Its representations stay locked up in its model. Too bad. Though still interesting.

As a side point- what's up with "propositional relational" representations? I dare say Murray Shannahan knows a thing or two more than me about logic, but I'm pretty sure I know this well: a representation is either relational, or it's propositional. A (first order) relation relates propositions. I don't get where this terminology comes from and it's a bit confusing.

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[1] https://github.com/metagol/metagol

What excites me about this and similar work (e.g. https://arxiv.org/abs/1904.12584) is that it augurs well for a new era of AI in which we combine the strength of deep learning (specifically, the teaching signal provided by automatic differentiation) and symbolic GOFAI (with its appeal to interpretability and traditional engineering principles).

Of course we need to keep the gradients, architecture search, hyperparameter tuning, scalable training to massive datasets, etc., but there is a growing sense that the programs we write can encode extremely powerful priors about how the world works, and to not encode those priors leaves our learning algorithms subject to attacks, bugs, poor sample efficiency, bad generalization, weak transfer. Not to mention a host of rickety conclusions that are probably poisoned by hyperparameter hacking.

Conversely, we need to try to avoid the proliferation of black box systems that require heroic efforts of mathematical analysis to understand and debug. Take for example the highly sophisticated activation atlas work by Shan Carter and others, which was needed to reveal that many convnets are vulnerable to an almost childlike kind of juxtapositional reasoning (snorkler + fire engine = scuba diver). Beautiful work, but to me it would be better if that form of analysis wasn't necessary in the first place, because the nets themselves were incapable of reasoning about object identity using distant context.

We need systems that are, by design, amenable to rigorous and lucid scientific analysis, that are debuggable, that admit simple causal models of their behavior, that are provably safe in various contexts, that can be straightforwardly interrogated to explain their poor or good performance, that suggest modification and elaboration and improvement other than adding more neurons. We need to speed the maturation of modern deep learning out of the alchemical phase into something more like aeronautical engineering.

The major innovations in recent years have been along these lines, of course. Attention is a great example, basically supplanting RNNs for a lot of sequence modelling. Convolutions themselves are probably the ur-example, of course. Graph convolutions will be the next major tool to be pushed into wider use. To the interested observer the stream of innovations seems not to end. But the framing that makes this all very natural is precisely that of this being the union of computer programming, where coming up with new algorithms for bespoke tasks is commonplace, with automatic differentiation, which allows those algorithm to learn.

What remains exciting virgin territory is how we best we put these new beasts into the harness of reliable AI engineering. That is in its infancy, because how you write and debug a learning program is completely different to the ordinary sort... there are probably 10x and 100x productivity gains to be realized there from relatively simple ideas.

What do you think should be a good benchmark for such hybrid models? Here they created a toy dataset of simple geometric shapes with simple relationships. This is fine to start with, but we need to come up with some more realistic and useful scenario. Even MNIST for image classification is both realistic and useful. I wonder what would be an equivalent of MNIST or ImageNet for models which implement reasoning and common sense.

There's CLEVR: http://openaccess.thecvf.com/content_cvpr_2017/papers/Johnso...

Looks good! So why didn't they use it in this paper?

"GOFAI" is a buzzword used by people who don't know how to make auditable systems, so they declare auditable systems "old fashioned" so-as to excuse themselves from learning them.

I don't know how you see that sentiment in what I wrote.

GOFAI is a slur against people who build systems responsibly, it doesn't matter the context for a slur just don't do it.

I haven't encountered it used with negative connotations, even by deep learning people. Neither does cursory Googling show it having that valence.

Just read your comment, it looks a very promising direction. I'd be glad to hear your response to my comment: https://news.ycombinator.com/item?id=20074750

>> We need systems that are, by design, amenable to rigorous and lucid scientific analysis, that are debuggable, that admit simple causal models of their behavior, that are provably safe in various contexts, that can be straightforwardly interrogated to explain their poor or good performance, that suggest modification and elaboration and improvement other than adding more neurons.

You mean specifically machine learning systems with these properties. Such machine learning systems do exist and have a big great body of research behind them: I'm talking about Inductive Logic Programming systems.

ILP has been around since the '90s (and even earlier without the name) and it's only the lack of any background in symbolic logic on the part of the most recent generation of neural net researchers that stops them from evaluating them, and using them to mine ideas to improve their own systems.

For a state-of-the-art ILP system, see Metagol (created by my PhD supervisor and his previous doctoral students):

https://github.com/metagol/metagol

Thanks! I see you are doing your PhD in ILP. As someone who is pondering the topic of his future PhD, the obvious question is: have ILP models been enriched with automatic differentiation? How? Did it help?

Either way, can you recommend a good survey article on ILP and the last few years of progress on that front?

Hi. ILP is Inductive Logic Programming, a form of logic-based, symbolic machine learning. ILP "models" are first-order logic theories that are not differentiable.

To put it plainly, most ILP algorithms learn Prolog programs from examples and background knowledge which are also Prolog programs. Some learn logic programs in other logic programming languages, like Answer Set Programming or constraint programming languages.

The wikipedia page on ILP has a good general introduction:

https://en.wikipedia.org/wiki/Inductive_logic_programming

The most recent survey article I know of is the following, from 2012:

(ILP turns 20 - Biography and future challenges) https://www.doc.ic.ac.uk/~shm/Papers/ILPturns20.pdf

It's a bit old now and misses a few recent developments, like learning in ASP and meta-interpretive learning (that I work on).

If you're interested specifically in differentiable models, in the last couple of years there has been a lot of activity on the side of mainly neural networks researchers interested in learning in differentiable logics. For an example, see this paper by a couple of people at DeepMind:

(Learning explanatory rules from noisy data) https://arxiv.org/abs/1711.04574

Edit: May I ask? Why is automatic differentiation the "obvious" question?

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