Friday, November 25, 2016

Getting the semantics right

In natural language "Getting the semantics right" means making sure other people understand you. It means picking the right words and putting them in right order, taking into account your intended audience of course.

In another sense you always  get the semantics "right" in natural language.  The semantics of a sentence is what it is, it is the perceived meaning of the sentence. There may be more or less of it however.  You don't choose the semantics, it chooses you .  Your sentence could be ambiguous, or (which is not the same thing) it could mean different things to different people. So yes, getting the semantics  wrong  means saying something that is either not understood at all, or easily misunderstood. ("Oh Lord, please don't let me …")

In programming "Getting the semantics right" is a more difficult thing. Not only do we have to pick the right statements to get our intention across to the machine.  We must INVENT new words, new APIs. The name of an API-method is like a word, a call to that API with some arguments is like a sentence.

Getting the semantics of new API-words and sentences right means their meaning, their effect must be easily understood in relation to other existing and new words and sentences and ways of using them. Getting the "API sentences" right is sometimes called "Fluent programming style" (

"Fluent" means easy to read, easy to understand, using exactly the right combination of words to convey your meaning with nuance and precision. Being fluent means using the language of your choice like a native speaker would.  In programming we must invent languages that _can be_  used fluently. But in programming there's more to it than just fluency because your API is creating a new language, there are no native speakers of it.

We could name our APIs arbitrarily, say with increasing numbers, API-1, API-2 etc.  Then "getting semantics right" would simply mean calling the right APIs. But we would never do that . Compilers do that. They turn our meaningful API-names into addresses of binary code entry-points.

Making API-method-names and  the possible ways of using them easy to understand means they must correspond to some real-world analogue. Example: "Search-Trees".  When they do  we can understand them in terms of that analogue, consistent with how we understand other words and sentence in terms of the same model. But it's not easy to come up with cohesive set of new words where understanding one term helps to understand the others.

In summary in programming getting semantics right means not only calling the right APIs but also coming up with API-method-names that are meaningful and consistent with other API-methods we "invent".  In programming there's more to "getting semantics right", than just picking the right words in right order. #fluent_programming

© 2016 Panu Viljamaa. All rights reserved

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