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Could someone explain why this or similar projects are useful?

by geuis 5y ago

coldtea 5y ago
For defining (and allowing users to touch) more powerful than static configuration and/or business logic, that you don't want to be turing complete.
fomojola 5y ago
It is a DSL for additional logic that can be: - Stored in your existing data store (assuming your data store can store a string) - Executed without eval() or any other potentially dangerous method - Executed in bounded time You think of things like Lua in Redis: this is one take on a not-quite-as-capable alternative for logic that can be safely executed in restricted environments (barring errors in the implementation of the parser). There will be editing/verification requirements: writing any moderately complex logic structure without a designer/test evaluator would be a nightmare, but as a generic way to specify/embed custom logic in a system that is language independent, has effectively no additional parser requirements (given that just about every single language has a JSON parser that is probably already in use in your project) it isn't a completely bad look. S-expression parsers do exist, but I'd wager many more people are familiar with the JSON parser in their language than the S-expression parser available in their language. I will say: it isn't complete. It lacks clarity about the behavior in the face of missing/invalid operation arguments. Something like {"<" : ["ham", 42]} I'd assume would throw an evaluation exception of some kind, but that should be clear in the spec. The playground at https://jsonlogic.com/play.html https://jsonlogic.com/play.html is a start, but before you try handing this to a non-developer, you'd really want a visual editor with node folding of some kind (so you can hide deeply nested structures away while you work on other things), variable completion (so you specify a sample data object and if you're typing in a variable you get completion options) and operator parameter verification (to stop you from writing in incorrect/unsupported values based on the operator).

Could someone explain why this or similar projects are useful?

by geuis 5y ago

Could someone explain why this or similar projects are useful?

For defining (and allowing users to touch) more powerful than static configuration and/or business logic, that you don't want to be turing complete.

fomojola 5y ago

It is a DSL for additional logic that can be: - Stored in your existing data store (assuming your data store can store a string) - Executed without eval() or any other potentially dangerous method - Executed in bounded time You think of things like Lua in Redis: this is one take on a not-quite-as-capable alternative for logic that can be safely executed in restricted environments (barring errors in the implementation of the parser). There will be editing/verification requirements: writing any moderately complex logic structure without a designer/test evaluator would be a nightmare, but as a generic way to specify/embed custom logic in a system that is language independent, has effectively no additional parser requirements (given that just about every single language has a JSON parser that is probably already in use in your project) it isn't a completely bad look. S-expression parsers do exist, but I'd wager many more people are familiar with the JSON parser in their language than the S-expression parser available in their language. I will say: it isn't complete. It lacks clarity about the behavior in the face of missing/invalid operation arguments. Something like {"<" : ["ham", 42]} I'd assume would throw an evaluation exception of some kind, but that should be clear in the spec. The playground at https://jsonlogic.com/play.html https://jsonlogic.com/play.html is a start, but before you try handing this to a non-developer, you'd really want a visual editor with node folding of some kind (so you can hide deeply nested structures away while you work on other things), variable completion (so you specify a sample data object and if you're typing in a variable you get completion options) and operator parameter verification (to stop you from writing in incorrect/unsupported values based on the operator).