| > Good abstraction layer: length prefix, or JSON encoding. > Bad abstraction layer: (...) In this context, it shouldn't matter. Sure, "mostly plaintext except some characters in some special positions..." is considered bad in modern engineering practice, however it's not fundamentally different or more difficult that printf and family. You wouldn't start calling printf without at least skimming the docs for the format string language, would you? > It is a bad engineering decision, and it also obfuscates the fact that there even is an abstraction layer unless you carefully read the spec. There's the rub: you should have read the spec. You should always read the spec, at least if you're doing something serious like production-grade software. With a binary or JSON-based protocol, you wouldn't look at few messages and assume you understand the encoding. I suppose we can blame SMTP for design that didn't account for human nature: it looks simple enough to fool people into thinking they don't need to read the manual. > There are very few good reasons to use a text-based data interchange format. If you mean text without obvious and well-defined structure, then I completely agree. > One of them is to make the format self-documenting, such that people can easily read and write it without consulting the spec. "Self-documenting" is IMHO a fundamentally flawed idea, and expecting people to read and write code/markup without consulting the spec is a fool's errand. > it should be binary - then you have to either read the spec or use someone else's implementation. That's mitigating (and promoting) bad engineering practice with protocol design; see above. I'm not a fan of this, nor the more general attitude of making tools "intuitive". I'd rather promote the practice of reading the goddamn manual. > But there's no excuse for the brain-dead approach that SMTP took. They didn't even use length prefixing, The protocol predates both JSON and XML by several decades. It was created in times when C was roaming the world; length prefixing got unpopular then, and only recently seems to en vogue. |