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I have genuinely no idea what this is saying. He was talking about "sensory keys" but the other person thought it was "requestor's keys"? That can't be it - be

I have genuinely no idea what this is saying. He was talking about "sensory keys" but the other person thought it was "requestor's keys"? That can't be it - because it's implied the other person heard the term "sensory". Can someone explain? (I must refrain from being very snarky and say that maybe the author is not very good at making points. Oops.)

throwoutway 5y ago
It looks like the context is missing. So the author assumes the audience is familiar with past knowledge about their OS (I clicked through to the main webpage) Still not sure what it means either
Twisol 5y ago
My read: there is something called a "key", and keys come in various kinds. If you only know that something is a key, the author says it should be clear that you can tell if something is a sensory key based only on its content. They explain that the adjective is part of the key's identity. Their collaborator notes that another kind of key, a "requester's key", cannot be distinguished just by the contents of the key itself; it's more about the context in which the key is used. The collaborator notes that "sensory key" could very well be the same kind of thing, if you don't already know any better. The author was surprised at how implicitly this knowledge was in their mind. They had attributed this feature to adjectives in general, not realizing the subtlety.
- OneLeggedCat 5y ago
  Your summary is better than the link.
abecedarius 5y ago
The starting point for this set of pages is http://www.cap-lore.com/CapTheory/ http://www.cap-lore.com/CapTheory/ and from there it recommends http://habitatchronicles.com/2017/05/what-are-capabilities/ http://habitatchronicles.com/2017/05/what-are-capabilities/ as basic intro (and so do I). The author was an architect of a 1970s/80s OS that's little known but that apparently influenced seL4 a lot. These pages aren't introductory but I'm glad they exist. A sensory key was a kind of transitive attenuator: it's like a read-only reference to an object such that if you use it to fetch a property from the object, the reference to the property that you get back is also a sensory key. (This is my understanding but I may be confused; I've only read about this OS.)
- kragen 5y ago
  FWIW if you talk to Jonathan Shapiro he will happily tell you that he was the one that convinced the L4 folks that capabilities were the right way to do things, replacing Liedtke's kind of lame chiefs-and-clans model. I think he's probably correct, because (quite aside from the particular encounters he describes) the resurgence of capability systems in the late 01990s owed an enormous amount to his work popularizing them. I'm pretty sure your memory of sensory keys is correct, but I haven't run KeyKOS either.
  - abecedarius 5y ago
    Thanks, I didn't know anything about the route of transmission.
Aicy 5y ago
I studied category theory at university and have no clue what he is talking about. It seems nonsensical and not well written. Edit: I realise this might be an unfair criticism since this is the author's private blog, and may expect readers to be very familiar with the topics he talks about. Hackernews is not likely not his intended audience, and the unrelated title of "Category Theory" does not help either.

throwoutway 5y ago

It looks like the context is missing. So the author assumes the audience is familiar with past knowledge about their OS (I clicked through to the main webpage) Still not sure what it means either

Twisol 5y ago

My read: there is something called a "key", and keys come in various kinds. If you only know that something is a key, the author says it should be clear that you can tell if something is a sensory key based only on its content. They explain that the adjective is part of the key's identity. Their collaborator notes that another kind of key, a "requester's key", cannot be distinguished just by the contents of the key itself; it's more about the context in which the key is used. The collaborator notes that "sensory key" could very well be the same kind of thing, if you don't already know any better. The author was surprised at how implicitly this knowledge was in their mind. They had attributed this feature to adjectives in general, not realizing the subtlety.

OneLeggedCat 5y ago
Your summary is better than the link.

abecedarius 5y ago

The starting point for this set of pages is http://www.cap-lore.com/CapTheory/ http://www.cap-lore.com/CapTheory/ and from there it recommends http://habitatchronicles.com/2017/05/what-are-capabilities/ http://habitatchronicles.com/2017/05/what-are-capabilities/ as basic intro (and so do I). The author was an architect of a 1970s/80s OS that's little known but that apparently influenced seL4 a lot. These pages aren't introductory but I'm glad they exist. A sensory key was a kind of transitive attenuator: it's like a read-only reference to an object such that if you use it to fetch a property from the object, the reference to the property that you get back is also a sensory key. (This is my understanding but I may be confused; I've only read about this OS.)

kragen 5y ago
FWIW if you talk to Jonathan Shapiro he will happily tell you that he was the one that convinced the L4 folks that capabilities were the right way to do things, replacing Liedtke's kind of lame chiefs-and-clans model. I think he's probably correct, because (quite aside from the particular encounters he describes) the resurgence of capability systems in the late 01990s owed an enormous amount to his work popularizing them. I'm pretty sure your memory of sensory keys is correct, but I haven't run KeyKOS either.
- abecedarius 5y ago
  Thanks, I didn't know anything about the route of transmission.

Aicy 5y ago

I studied category theory at university and have no clue what he is talking about. It seems nonsensical and not well written. Edit: I realise this might be an unfair criticism since this is the author's private blog, and may expect readers to be very familiar with the topics he talks about. Hackernews is not likely not his intended audience, and the unrelated title of "Category Theory" does not help either.