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View Code? Open in Web Editor NEWProposed documentation for alloytools.org
License: MIT License
Proposed documentation for alloytools.org
License: MIT License
The link to "here" in the readme is broken (points to https://github.com/hwayne/alloydocs/blob/master which triggers a page not found). Is it supposed to point to https://github.com/hwayne/alloydocs/tree/master
maybe?
I noticed there are no links to https://alloy.readthedocs.io/en/latest/ when browsing the github project, I believe the description of the project is the right place to store that information.
Love the new docs. I made some notes as I was going through:
r: some A states that there is at least one A in the relation.
But the image shows one
multiplicity. Each book has one author.
univ.rel is the domain of rel
This is range. Domain is rel.univ
.
We can write both ~^edge and ~^edge.
These two are the same. Perhaps one of them is supposed to be ^~edge
?
*edge = ^edge + iden
Not strictly true, I hope. I am curious, though, does *(A->B)
contain B->B
?
rel1 ++ rel2 = rel1 - (univ.rel2 <: rel2) + rel2
I believe this should be (rel2.univ <: rel1)
. Also "shared relationships" is not clearly defined.
=> can also be used as a constraint.
This confused me. I believe the =>
operator hasn't been introduced yet at this point of a linear reading. And the link on "constraint" wasn't to anything that would define that term.
Bar expressions
It is unclear if the newline after the |
is required.
To say that A is not a subset of B, you can write A !in B, A not in B, !(A in B), etc.
It was surprising to find !in
given such little attention, since it is definitely a thing in other languages.
Relational Quantifiers
It is surprising that you can use some
but not no
. Also why isn't all
supported when you can just write it with chained quantifiers?
all e: rel | P[e]
≡ all x: rel.univ | all y: x.rel | P[x->y]
I like to use a vertical monitor off to the side for reading documentation as I work. On the Alloy page, the left index bar takes up a large amount of screen space:
It would be nice if the index bar could be collapsed, similar to in the Python docs: https://python.readthedocs.io/en/latest/index.html
I’d like to contribute to this documentation, but I can’t find any licensing information in the repository. Am I missing something?
Thank you.
It's been almost a year, c'mon man
Version 5.0 added support for Markdown syntax.
Even just importing the linked docs verbatim would be useful. Heck, I can submit that as a PR if you're supportive.
The wording of
https://github.com/hwayne/alloydocs/blame/master/language/signatures.rst#L472
If you make a signature ``abstract``, then all instances of the
signature will be extensions, and there will be no signatures that are
still the base.
confuses me - what is the base? "still the base" signature? maybe "only the base signature"?
And is "base" defined somewhere? Or does this mean supertype of a suptype?
Provide the example of #univ
in the evaluator
Welcome to the Alloy Documentation!¶
— strange title
Each model will have some number of each signature, called atoms. Take the following spec:
The following would be a valid model:
— uses model in two different ways
We don’t just care that there are people and accounts, we care which people have which accounts.
— Odd that this introduces an example that doesn’t relate to the example that follows in the code
Standard convention is to prefix every relation with a comma.
— your convention maybe :-)
— commas motivated in part by ability to write inline: sig A {b: C, c: C}
Alloy can generate models where a relation points to the same atom.
— not clear what this means
Each relation has a multiplicity, which represents how many atoms it can include. If you do not include a multiplicity, it’s assumed to be one.
— not true for relation with arity > 2
, edge: set Node - this
— more natural to call this field “adjacents” or even “edges”, or do you mean it to represent a hyperedge?
Using the dot operator, if access = P -> C -> D, then P.access = C -> D and access.D = P -> C.
— introducing this for multi relations. why not for relations?
As an aide, use the following table:
— aid?
— why the “used” terminology? I’m not sure what it means.
If you make a signature abstract, then all instances of the signature will be extensions
— what does instances mean here?
Then the b relation can include A -> C, but c cannot include A -> B.
— not sure what “can include” means. i think there’s an instance in which c does include A->B.
In sets and relations:
All elements of a set must have the same arity, but can otherwise freely mix types of elements.
— Seems misleading to me: elements cannot be sets or relations.
Adding a signature automatically defines the set of all atoms in that signature. Given
— Perhaps confusing? signature name also the name of a set?
univ -> univ is the set of all possible relations in your model.
— the largest relation?
one sig U1, U2 extends User {}
— not sure it’s clear how the relation U1 relates to the atom U1
Return every element that elements in Set map to, via rel. This also works for individual atoms.
— typo
We can use the dot operator with two relations. It returns the inner product of the two relations.
— Note that dot isn’t overloaded: it’s the same operator in every case. I think it’s important to point this out.
This is mostly useful for directly manipulating relations. For example, given a set S, we can map every element to itself by doing S <: iden.
— also useful for disambiguating field names
A bar expression is one of the form:
— but let also has a bar?
— other quantifiers eventually go here?
— looks like you have quants later, so this is a remnant?
one and lone behave unintuitively when used in multiple quantifiers.
— actually, i think they behave intuitively — as your explanation following this suggests. the problem is that the shorthand rule (that you can expand Q x, y | into Q x | Q y) doesn’t hold.
The following truth table will satisfy clause (2) but not (1):
— maybe better to use S1 and S2 rather than A, B?
The parameters of a function (or predicate) can shadow a global value. In this case, you can retrieve the original global value by using @Val.
— I have no recollection of this!
Commands
— useful to be able to attach labels to commands
foo: check…
so they appear in menu
Tooling
The analyzer converts the model into a SAT expression to solve. S
— SAT instance? SAT formula?
Techniques
Then the boolean can be tested with a in PremiumAccount. This method has a number of advantages:
— also can write things like
PremiumAccount.owner in Member
rather than
all a: Account | a.premium = true implies a.owner in Member
If subtyping is insufficient, you can also use the boolean module. This is generlaly not recommended.
— typo
Dynamic Models
— would be nice to include events, which visualize better than predicates
https://alloy.readthedocs.io/en/latest/language/signatures.html#abstract
I believe the example should be :
abstract sig Machine {}
sig Broken in Machine {}
sig Server extends Machine {}
sig Client extends Machine {}
To show that you can have Clients or Servers possibly in Broken but no Machines, or Broken Machines.
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