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I'm having a hard time thinking of a way code can ever be fully decoupled from data. When we decide it's better to have a name field rather than firstName and l

I'm having a hard time thinking of a way code can ever be fully decoupled from data. When we decide it's better to have a name field rather than firstName and lastName does that mean we simplify NameCalculation.fullName to just return data.name? This seems to suggest we still have coupled code to data (the data structure being an object), it's just now a coupled function, but you have decoupled it enough to use NameCalculation in different contexts. Single responsibility classes are already recommended for reuse like this in OO. Also when it comes to data validation, OO performs all of this validation too and in a much more compact and code-oriented, extensible way. Why would I write a separate schema when the object itself knows what it will accept, what is optional, and what range the values should be in? I'd imagine the schema and code could become incoherent.

drpyser22 4y ago
For validation, this approach would have you write a set of functions to validate the properties of the data. Nothing forbids a function that applies validation to inputs before returning a data object? Extensibility can be done through functional means(e.g. higher order functions, function composition, lens) or oop(strategy pattern and equivalents, code object composition and inheritance,...). Not sure what you mean by more compact and code-oriented? Code is always coupled to an interface, implicitly or explicitly. In the case of oop, code is coupled to the class, which can represent something specific with very concrete semantics (e.g. employee, author) or something generic that is meant to be subclassed(e.g. person).
snidane 4y ago
> Why would I write a separate schema when the object itself knows what it will accept, what is optional, and what range the values should be in? Because data is just data and the meaning to it is given at the time of application. If you want to couple validation to the data itself - how do you decide which N of the meanings to validate against?
- galaxyLogic 4y ago
  No, data must have meaning, else it is meaningless. If you want to process the data you must use some language to access parts of the data. Data must have a symbolic representation, not juts be 1s and zeros. Or it can be a bit-stream, but even then you need a language that knows the different between 1 and 0. person.name extracts the field 'name' from the data. To manipulate the data, the program must know that there is such a field as 'name' it can ask for.
ajuc 4y ago
I think in Data Oriented Programming it's fine for your code to depend on data structure. You want to separate code and data, not to decouple them. As for why see for example Command Query Separation (the data oriented way) vs Tell Don't Ask (the encapsulate everything way).
dustingetz 4y ago
to use Rich Hickey’s definitions, data is an observation or measurement at a point in time. [:fullname “John Doe” t1] [:first “John” t1] no code needed to see the denormalization. Which came from the symbolic model that was chosen. the code only exists to translate between incompatible data models of a program’s inputs and outputs.
weavejester 4y ago
Just imagine you're sending the data across a network, instead of between local functions. If you have a web service that spits out JSON, then you have data that is decoupled from code. That's not to say that the JSON data isn't then read and manipulated by code; just that no specific code is associated with the data. As for why you'd want to do this, well, one reason is that it makes it easier to bounce data between different services. You don't need to perform any sort of conversion if you're operating directly on the data you're receiving and sending. The second argument for this style is perhaps more ideological. In the Clojure community in particular, complexity is seen as arising from coupled components. The more things you can decouple, the less complex your codebase. The less complex your codebase, the more reliable and extensible it is. Edit: another potential advantage is that its easier to use generic functions to interrogate and manipulate data that isn't encapsulated in specific types or objects.
- theteapot 4y ago
  > Just imagine you're sending the data across a network, instead of between local functions. If you have a web service that spits out JSON, then you have data that is decoupled from code. That's not to say that the JSON data isn't then read and manipulated by code; just that no specific code is associated with the data. That's not really true in classical OO or DOP. There is always code that depends on specifics of some data. In classical OO it's extremely common to de-marshal data straight off the wire and into a class (AKA hydration). From then on the thing that interacts with the data structure directly is the object instance.
skippyboxedhero 4y ago
Because the problem in OO is if you have any kind of cross-cutting concern, then it collapses totally. For example, I have a Wizard object. My wizard has a wand, we store the wand object on our Wizard object. Simple. But then my wizard casts a spell, and does damage to a goblin. Do we put the cast method on the wand, the wizard? There is no real reason to pick one over the other (this problem comes up a lot with game development, which is why this pattern is more common there...Spring is another example, aspect-oriented programming/dependency injection works from similar principles). It is far easier to separate that out totally and have a pure, reusable cast function that takes the wizard, goblin, and weapon. Another aspect of this problem (which Rust, as an example, makes clear) is that you introduce runtime bugs or hurt performance when you start carrying around a lot of references everywhere. Once you start to think about what actually needs a reference to another object (in Rust, this is limited by the borrow checker) then you realise why OOP doesn't work in some cases. OO doesn't perform validation, your code performs validation on the data. You can write a separate schema, you can write one schema, but the problem is that OOP tries to fit a round peg in a square hole with some applications. Very generally, it is harder to make mistakes if you use something like data-oriented. If you have a lot of code with calculations or interactions, it is very pure, easy to test, and fits well with how people think about those elements (one area I have found is financial applications, I actually worked this out and then found out data-oriented program existed when building financial-related stuff). In these cases, introducing OOP means state changing in unpredictable ways (and then someone comes into the project, doesn't understand the abstraction, calls a method that is named erroneously and it all goes wrong).
- treis 4y ago
  >But then my wizard casts a spell, and does damage to a goblin. Do we put the cast method on the wand, the wizard? There is no real reason to pick one over the other You did pick: "My wizard casts a spell". The cast method goes on the wizard.
  - 411111111111111 4y ago
    Unless cast is an ability unlocked by the wand, then you'd only have "use main/offhand" on the person, and the cast would be on the wand. It's really not as cut and dry as you said.
randcraw 4y ago
These examples spring to mind: 1) high performance computing (vector processing / SIMD), 2) deep neural nets, 3) graphics. Each of these computation models process a small number of large blocks of data whose efficient movement is just as important as their efficient number crunching. OOP doesn't serve those emphases as well as DOP does.
roenxi 4y ago
Code is itself data, so a full decoupling is logically impossible. Data is going to have an implicit schema regardless because that is just how data works. And once there is a schema, it may as well be expressed explicitly independently of the code because then you get the whole basket of standard schema operations for free (validate the data against a schema, provide a schema to an external consumer when moving data around, talking/operating more generally on schema to manipulate data, generating glue code or APIs programmatically). Your description sounds like you are using your objects as schema references which is fine, but if there is a 1:1 correspondence with schema then you are already doing data oriented programming, and if there isn't then you can't have 3rd party libraries that support schema-based operations. And losing those schema-based operations hasn't gained anything because the data still has a schema, it just isn't well organised. TLDR; Data oriented programming isn't essential. But if you plan on passing data around between systems schema should be mandatory, and if you pass data around within a system schema are recommended. > Why would I write a separate schema when the object itself knows what it will accept, what is optional, and what range the values should be in? In practice, I have seen a fair number of complex objects where that information is obscure. If there isn't an explicit schema there is a chance of bugs where the object doesn't understand the data it is ingesting and that it won't share its knowledge that there is a problem until it fails in some obscure way in runtime. It wastes a lot of time fixing those bugs because the easiest way to clean that up is to tease out an explicit schema & start thoroughly validating inputs.
- deltaonefour 4y ago
  > Code is itself data, so a full decoupling is logically impossible. Nah, code exists in a different universe then "data" and it's decoupled by default. Runtime data is completely unaware of "code." that is unless you do something called "reflection" which is sort of a rarely used feature.
oivey 4y ago
OO schemas are very strict and in many situations difficult to extend. For example, let's say you have a class named Name that contains firstName and lastName. Let's say that you have a function that consumes lists of Names. Let's say you have yet another class called OtherName that contains firstName and lastName. That class will not be compatible with the function. Usual OOP suggests you solve this via inheritance, but if you don't own Name or OtherName that won't help you. OOP's tools for polymorphism are very limited, especially if you don't own all the code you're trying to use (third party libraries). If the "schema" enforced by the type system didn't include the name of the object that opens up a lot of possibilities.
- jcelerier 4y ago
  > OO schemas are very strict I mean, it's the whole point. You want to have something that will give you compile errors whenever you change anything to make sure that you go all over the cases where the change has an impact
  - oivey 4y ago
    The goal of OOP or any programming system is to help you enforce invariants to improve correctness of a program. “has String members ‘firstName’ and ‘lastName’” is a perfectly reasonable invariant that isn’t all that well served by traditional OOP. You can’t strictly enforce the invariant I just stated via OOP. You can only define tangentially related concepts via inheritance.
    - jcelerier 4y ago
      > You can’t strictly enforce the invariant I just stated via OOP. but you can strictly enforce it in pretty much every relevant OOP language - Java, C#, C++, C, Rust, D, ... by defining a class / struct / record with these two members, which is the only thing that matters. No one programs in abstract design principles, only in actual programming languages.
      - oivey 4y ago
alphanumeric0 4y ago
Thank you for all of the different viewpoints, it's starting to make sense now. I've used JSON schema before in one of my previous projects. I'll keep it in mind for next time.
deltaonefour 4y ago
If you have a hard time thinking this way then you really need to try other paradigms in coding because OOP is not the only way and it is getting less and less popular. For example C, is not OOP. Linus Torvalds hates OOP, so linux is in written in C. Go was created by Robert Pike who's also subtly against it, and it shows in the language. Additionally Rust pretty much gets rid of objects as well. React is also moving away from class based representation of components. These are just modern languages that are moving away from OOP. In addition to this... behind the modern languages there's a whole universe and history of other styles of programming. Not against OOP... But I'm saying it's not a good sign if OOP is the only perspective you're capable of seeing.
- discreteevent 4y ago
  I think all of your examples allow encapsulation of data behind polymorphic interfaces. So, not data oriented. This includes the Linux kernel [1] https://www.cs.cmu.edu/%7Ealdrich/papers/objects-essay.pdf https://www.cs.cmu.edu/%7Ealdrich/papers/objects-essay.pdf
  - deltaonefour 4y ago
    Polymorphism and encapsulation are not features exclusive to OOP. Isomorphisms exist everywhere. You could say nothing is OOP because it compiles into assembly anyway where pretty much all those concepts don't even exist. You can even say all of assembly can decompile into OOP so everything is OOP. Think about it. If linus torvolds hates OOP. What is it that he hates? You can say, Linus is an idiot and everything is OOP so he's wrong. Or you can understand what is it about OOP that he hates and understand the delta between my examples and what is traditionally thought of as OOP. None* of my examples contain a class. That should be a hint, as that syntax is pretty much used in most OOP languages. *React still contains class based components except the creators now recommend moving away from class based syntax to functional components.

drpyser22 4y ago

For validation, this approach would have you write a set of functions to validate the properties of the data. Nothing forbids a function that applies validation to inputs before returning a data object? Extensibility can be done through functional means(e.g. higher order functions, function composition, lens) or oop(strategy pattern and equivalents, code object composition and inheritance,...). Not sure what you mean by more compact and code-oriented? Code is always coupled to an interface, implicitly or explicitly. In the case of oop, code is coupled to the class, which can represent something specific with very concrete semantics (e.g. employee, author) or something generic that is meant to be subclassed(e.g. person).

snidane 4y ago

> Why would I write a separate schema when the object itself knows what it will accept, what is optional, and what range the values should be in? Because data is just data and the meaning to it is given at the time of application. If you want to couple validation to the data itself - how do you decide which N of the meanings to validate against?

galaxyLogic 4y ago
No, data must have meaning, else it is meaningless. If you want to process the data you must use some language to access parts of the data. Data must have a symbolic representation, not juts be 1s and zeros. Or it can be a bit-stream, but even then you need a language that knows the different between 1 and 0. person.name extracts the field 'name' from the data. To manipulate the data, the program must know that there is such a field as 'name' it can ask for.

ajuc 4y ago

I think in Data Oriented Programming it's fine for your code to depend on data structure. You want to separate code and data, not to decouple them. As for why see for example Command Query Separation (the data oriented way) vs Tell Don't Ask (the encapsulate everything way).

dustingetz 4y ago

to use Rich Hickey’s definitions, data is an observation or measurement at a point in time. [:fullname “John Doe” t1] [:first “John” t1] no code needed to see the denormalization. Which came from the symbolic model that was chosen. the code only exists to translate between incompatible data models of a program’s inputs and outputs.

weavejester 4y ago

Just imagine you're sending the data across a network, instead of between local functions. If you have a web service that spits out JSON, then you have data that is decoupled from code. That's not to say that the JSON data isn't then read and manipulated by code; just that no specific code is associated with the data. As for why you'd want to do this, well, one reason is that it makes it easier to bounce data between different services. You don't need to perform any sort of conversion if you're operating directly on the data you're receiving and sending. The second argument for this style is perhaps more ideological. In the Clojure community in particular, complexity is seen as arising from coupled components. The more things you can decouple, the less complex your codebase. The less complex your codebase, the more reliable and extensible it is. Edit: another potential advantage is that its easier to use generic functions to interrogate and manipulate data that isn't encapsulated in specific types or objects.

theteapot 4y ago
> Just imagine you're sending the data across a network, instead of between local functions. If you have a web service that spits out JSON, then you have data that is decoupled from code. That's not to say that the JSON data isn't then read and manipulated by code; just that no specific code is associated with the data. That's not really true in classical OO or DOP. There is always code that depends on specifics of some data. In classical OO it's extremely common to de-marshal data straight off the wire and into a class (AKA hydration). From then on the thing that interacts with the data structure directly is the object instance.

skippyboxedhero 4y ago

Because the problem in OO is if you have any kind of cross-cutting concern, then it collapses totally. For example, I have a Wizard object. My wizard has a wand, we store the wand object on our Wizard object. Simple. But then my wizard casts a spell, and does damage to a goblin. Do we put the cast method on the wand, the wizard? There is no real reason to pick one over the other (this problem comes up a lot with game development, which is why this pattern is more common there...Spring is another example, aspect-oriented programming/dependency injection works from similar principles). It is far easier to separate that out totally and have a pure, reusable cast function that takes the wizard, goblin, and weapon. Another aspect of this problem (which Rust, as an example, makes clear) is that you introduce runtime bugs or hurt performance when you start carrying around a lot of references everywhere. Once you start to think about what actually needs a reference to another object (in Rust, this is limited by the borrow checker) then you realise why OOP doesn't work in some cases. OO doesn't perform validation, your code performs validation on the data. You can write a separate schema, you can write one schema, but the problem is that OOP tries to fit a round peg in a square hole with some applications. Very generally, it is harder to make mistakes if you use something like data-oriented. If you have a lot of code with calculations or interactions, it is very pure, easy to test, and fits well with how people think about those elements (one area I have found is financial applications, I actually worked this out and then found out data-oriented program existed when building financial-related stuff). In these cases, introducing OOP means state changing in unpredictable ways (and then someone comes into the project, doesn't understand the abstraction, calls a method that is named erroneously and it all goes wrong).

treis 4y ago
>But then my wizard casts a spell, and does damage to a goblin. Do we put the cast method on the wand, the wizard? There is no real reason to pick one over the other You did pick: "My wizard casts a spell". The cast method goes on the wizard.
- 411111111111111 4y ago
  Unless cast is an ability unlocked by the wand, then you'd only have "use main/offhand" on the person, and the cast would be on the wand. It's really not as cut and dry as you said.

randcraw 4y ago

These examples spring to mind: 1) high performance computing (vector processing / SIMD), 2) deep neural nets, 3) graphics. Each of these computation models process a small number of large blocks of data whose efficient movement is just as important as their efficient number crunching. OOP doesn't serve those emphases as well as DOP does.

roenxi 4y ago

Code is itself data, so a full decoupling is logically impossible. Data is going to have an implicit schema regardless because that is just how data works. And once there is a schema, it may as well be expressed explicitly independently of the code because then you get the whole basket of standard schema operations for free (validate the data against a schema, provide a schema to an external consumer when moving data around, talking/operating more generally on schema to manipulate data, generating glue code or APIs programmatically). Your description sounds like you are using your objects as schema references which is fine, but if there is a 1:1 correspondence with schema then you are already doing data oriented programming, and if there isn't then you can't have 3rd party libraries that support schema-based operations. And losing those schema-based operations hasn't gained anything because the data still has a schema, it just isn't well organised. TLDR; Data oriented programming isn't essential. But if you plan on passing data around between systems schema should be mandatory, and if you pass data around within a system schema are recommended. > Why would I write a separate schema when the object itself knows what it will accept, what is optional, and what range the values should be in? In practice, I have seen a fair number of complex objects where that information is obscure. If there isn't an explicit schema there is a chance of bugs where the object doesn't understand the data it is ingesting and that it won't share its knowledge that there is a problem until it fails in some obscure way in runtime. It wastes a lot of time fixing those bugs because the easiest way to clean that up is to tease out an explicit schema & start thoroughly validating inputs.

deltaonefour 4y ago
> Code is itself data, so a full decoupling is logically impossible. Nah, code exists in a different universe then "data" and it's decoupled by default. Runtime data is completely unaware of "code." that is unless you do something called "reflection" which is sort of a rarely used feature.

oivey 4y ago

OO schemas are very strict and in many situations difficult to extend. For example, let's say you have a class named Name that contains firstName and lastName. Let's say that you have a function that consumes lists of Names. Let's say you have yet another class called OtherName that contains firstName and lastName. That class will not be compatible with the function. Usual OOP suggests you solve this via inheritance, but if you don't own Name or OtherName that won't help you. OOP's tools for polymorphism are very limited, especially if you don't own all the code you're trying to use (third party libraries). If the "schema" enforced by the type system didn't include the name of the object that opens up a lot of possibilities.

jcelerier 4y ago
> OO schemas are very strict I mean, it's the whole point. You want to have something that will give you compile errors whenever you change anything to make sure that you go all over the cases where the change has an impact
- oivey 4y ago
  The goal of OOP or any programming system is to help you enforce invariants to improve correctness of a program. “has String members ‘firstName’ and ‘lastName’” is a perfectly reasonable invariant that isn’t all that well served by traditional OOP. You can’t strictly enforce the invariant I just stated via OOP. You can only define tangentially related concepts via inheritance.
  - jcelerier 4y ago
    > You can’t strictly enforce the invariant I just stated via OOP. but you can strictly enforce it in pretty much every relevant OOP language - Java, C#, C++, C, Rust, D, ... by defining a class / struct / record with these two members, which is the only thing that matters. No one programs in abstract design principles, only in actual programming languages.
    - oivey 4y ago

alphanumeric0 4y ago

Thank you for all of the different viewpoints, it's starting to make sense now. I've used JSON schema before in one of my previous projects. I'll keep it in mind for next time.

deltaonefour 4y ago

If you have a hard time thinking this way then you really need to try other paradigms in coding because OOP is not the only way and it is getting less and less popular. For example C, is not OOP. Linus Torvalds hates OOP, so linux is in written in C. Go was created by Robert Pike who's also subtly against it, and it shows in the language. Additionally Rust pretty much gets rid of objects as well. React is also moving away from class based representation of components. These are just modern languages that are moving away from OOP. In addition to this... behind the modern languages there's a whole universe and history of other styles of programming. Not against OOP... But I'm saying it's not a good sign if OOP is the only perspective you're capable of seeing.

discreteevent 4y ago
I think all of your examples allow encapsulation of data behind polymorphic interfaces. So, not data oriented. This includes the Linux kernel [1] https://www.cs.cmu.edu/%7Ealdrich/papers/objects-essay.pdf https://www.cs.cmu.edu/%7Ealdrich/papers/objects-essay.pdf
- deltaonefour 4y ago
  Polymorphism and encapsulation are not features exclusive to OOP. Isomorphisms exist everywhere. You could say nothing is OOP because it compiles into assembly anyway where pretty much all those concepts don't even exist. You can even say all of assembly can decompile into OOP so everything is OOP. Think about it. If linus torvolds hates OOP. What is it that he hates? You can say, Linus is an idiot and everything is OOP so he's wrong. Or you can understand what is it about OOP that he hates and understand the delta between my examples and what is traditionally thought of as OOP. None* of my examples contain a class. That should be a hint, as that syntax is pretty much used in most OOP languages. *React still contains class based components except the creators now recommend moving away from class based syntax to functional components.