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    Components of Hadoop Architecture Computer Science

    Components of Hadoop Architecture

    Posted: 11 May 2021 12:08 AM PDT

    Is algebraic semantics a form of axiomatic semantics or a form of denotational semantics?

    Posted: 04 May 2021 03:30 PM PDT

    https://en.wikipedia.org/wiki/Semantics_(computer_science)#Variations says

    Algebraic semantics is a form of axiomatic semantics based on algebraic laws for describing and reasoning about program semantics in a formal manner;

    https://en.wikipedia.org/wiki/Algebraic_semantics_(computer_science) also says

    In computer science, algebraic semantics is a form of axiomatic semantics based on algebraic laws for describing and reasoning about program semantics in a formal manner.

    But p326 in Eric G. Wagner (1995). "Algebraic Semantic". In Samson Abramsky; Dov M. Gabbay; Thomas S. E. Maibaum (eds.). Handbook of Logic in Computer Science: Semantic structures. 3. (cited in https://en.wikipedia.org/wiki/Algebraic_semantics_(computer_science)#References) says

    While the term 'algebraic semantics' is frequently used to refer to forms of denotational semantics employing algebraic concepts (e.g., see [Gordon, 1979]) or to the algebraic specification of data types, [Goguen et a/., 1978], the more restricted usage employed here goes back at least to Guessarian's book [Guessarian, 1981].

    So is algebraic semantics a form of axiomatic semantics or a form of denotational semantics?

    Thanks.

    submitted by /u/timlee126
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    Is Hoare logic really axiomatic semantics of a programming language?

    Posted: 04 May 2021 09:00 AM PDT

    Is Hoare logic really axiomatic semantics of a programming language?

    Is Hoare logic instead about the language of Hoare triples (specifically, a proof system over the language of Hoare triples) ?

    What is the axiomatic semantics of a programming language, which is related or induced by Hoare logic then?

    Thanks.

    submitted by /u/timlee126
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    Posted: 03 May 2021 11:42 AM PDT

    Are Empty statement axiom and domain axioms the same thing in Hoare logic?

    Posted: 04 May 2021 07:35 AM PDT

    Ben-Ari's logic book says

    Definition 15.8 (Deductive system H L )

    Domain axioms: Every true formula over the domain(s) of the program variables.

    1. What do domain axioms mean? Can they be formulated into a mathematical statement?

    2. https://en.wikipedia.org/wiki/Hoare_logic#Rules doesn't have the domain axioms, but Empty statement axiom, while the book doesn't Empty statement axiom but domain axioms. Are Empty statement axiom and domain axioms the same thing in Hoare logic?

    Thanks.

    submitted by /u/timlee126
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    Posted: 04 May 2021 02:40 AM PDT

    [Discussion] A class should have state or dependencies, but not both

    Posted: 04 May 2021 12:38 AM PDT

    This principle "feels" right, but I'm working through trying to formulate it properly.

    Consider a point class (in pseudo-code because lazy):

    class Point private x, y construct(x, y) draw(Drawable surface)

    (Instead of surface, it could also be a save-function with a database connection as argument (or indeed any type of persistence)).

    If the surface was instead injected into the constructor, the point would look like:

    class Point private x, y, surface constructor(x, y, surface)

    Isn't that weird, to have two properties related to state, and then a third property related to something completely different? Especially when it's something effectful, like drawing or writing to disk.

    On the other hand, you can imagine a command object class like this:

    class InstallApp private db, io, logger, mailer constructor(db, io, logger, mailer) execute(app)

    In this case, all dependencies are effectful classes. Makes more sense, right? And then the app class has only "pure" properties, like User or Configuration.

    A rectangle depending on points is also OK, since the points are pure:

    class Rectangle private bottomLeft, topRight constructor(Point bottomLeft, Point topRight) // draw, save, etc

    Another way to phrase it is that classes should only depend on other classes in the same layer (domain layer vs "effectful" layer).

    The major drawback is that no language can actually distinguish between a dependency and "normal" class property. Possibly they should have different semantics? Or the possibility to separate pure and effectful classes.

    Thoughts?

    submitted by /u/usernameqwerty005
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    Posted: 03 May 2021 10:42 PM PDT

    Is Hoare logic a logic system or a theory in some logic system?

    Posted: 03 May 2021 04:10 PM PDT

    (1) p872 of http://www.worldcolleges.info/sites/default/files/aaby.pdf says

    The axiomatic semantics of a programming language define a mathematical theory of programs written in the language.

    In the first logic system, a theory is a set of sentences closed under |- or |=.

    Is Hoare logic a theory in some logic system (such as propositional logic, first order logic)? If yes, which logic system?

    Or is Hoare logic a logic system itself?

    (2) If Hoare logic is a logic system itself, https://en.wikipedia.org/wiki/Hoare_logic says

    Hoare logic (also known as Floyd–Hoare logic or Hoare rules) is a formal system with a set of logical rules for reasoning rigorously about the correctness of computer programs.

    while https://en.wikipedia.org/wiki/First-order_logic says

    First-order logic is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science.

    In the first order logic system, nonlogical symbol sets are up to choice, and for different nonlogical symbol sets, there are different formal first order languages.

    In Hoare Logic, is it only one formal system and only one formal language? Or is it like the first order logic system, where there are multiple formal systems (i.e. multiple formal languages)?

    Does Hoare logic only have one proof system, while FOL can have multiple equivalent proof systems (e.g. Sequent calculus, Hilbert system)?

    Does Hoare logic have semantics, as FOL has semantics?

    Thanks.

    submitted by /u/timlee126
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