Tuesday, September 10, 2013

Scripts Part I - What is a script?

Let's Define!

My current definition of a script is:

A set of instructions made explicit by one agent such that another (or the same) agent can later interpret them in order to replicate a process to achieve a desired outcome or behaviour.

So a script is, essentially, a communication tool. It can be verbal or written, it can be instructions to follow in order or a set of unordered instructions, but it is always done with the intention that the instructions will be followed by someone or something.

Here are some examples of scripts:
A computer program
A food recipe
A shopping list
A checklist


Implicit information in communication

When humans talk to each other we express two elements of communication. In pragmatics they are known as explicature and implicature. Explicature is what is actually said; for example "We went shopping, had a meal and ended up in the cinema". Implicature is what is implied by what is said. In the above example one might assume that going shopping, having a meal and ending up in a cinema happened in that order, but the sentence remains logically true even if the order is changed. There's also an implication that going to the cinema involved watching a film as part of a day out but the sentence remains logically true if the group stepped into a cinema then turned around and immediately walked out.

These two elements of communication are important when considering the audience for a script - the script has to be interpreted in order to be followed and that's what will affect the outcome of behaviour that actually happens (as opposed to the one desired by the script author)

Computers vs People

A computer program is a kind of script. It's a set of instructions made explicit by a programmer that the computer follows to execute the intentions of the programmer. Computers only pay attention to explicature in script instructions. This can be translated into the more common phrase "computers only do what you tell them to do".

Computer scripts may fail because computers are very picky about their explicature (they must be syntactically accurate). It may fail because the computer will execute the script as it exists while ignoring implicit desires. Just because you write a comment in the script saying "this function will return the square root of a number" does not mean it will. Just because you used a variable name called "square_root_of_input" does not mean that's what the variable contains - and your computer cannot care. We write unit tests in code as a way to try to ensure that the behaviour of the code we write matches our intended purpose - those are the lengths we go to to compensate for how mindless computers are and how literally they interpret our scripts.

Computers ignore implicature. They ignore context. And this is why they're so difficult to communicate with - human language is rife with implicature. We put up with this communications issue because computers are able to perform tasks (even ones that we are bad at or find impossible) in volume at an enormous rate.

A food recipe is a kind of script. It is a set of instructions made explicit by a person so that a (often) different person can follow them in order to end up with similar food. People have many powers that computers lack. They can understand implicit and tacit information. A recipe may fail because of a misunderstanding concerning implicit information. In the UK "crumble 3 plain biscuits" probably means McVities Digestives. In the US "biscuits" are basically a small bread a bit like a nearly tasteless scone. Try making a biscuit base with those.

Because it's followed by a person a recipe can have certain implicit or tacit information in it. For example if I'm told to use "self-raising flour" and I don't have any perhaps I might use plain flour and a leavening agent. The explicature is "add 200g self-raising flour". The implicature is "add something that has similar properties of 200g self-raising flour in the context of baking the pie this recipe describes". I know I can probably skip the "Add almonds" step but I can't very well skip "Bake at 180C for 40 minutes" because I can guess how differently they will affect the quality of the end product. This is the power humans have over computers.

Scripts in Testing

Automated Testing

Computers will interpret only the literal truth of explicature in scripts. This is the essence of checking to me - ignorance of implicature. This is a price we pay in exchange for speed - computers are much faster at making these checks.

Manual Scripts

Humans will interpret the implicature of a script. Humans are UNABLE to ignore implicature, we are simply not wired for it. It's part of our emotions. It's how we can process information in a heuristic way - not always accurately but with the efficiency to be evolutionarily successful. It's how we communicate complex ideas and their impact. It's what allows us to create art.

This means we cannot perform checks (under the strictest definition of check). A human check, I suppose, is the absence of knowledge to guide implicature in specific observations while making an evaluation in a product - we still make certain natural inferences but we can try to ignore parts of the context or try to behave as if we don't know the context in order to make a simple confirmation of the truth value of the explicature of an instruction (or what would be the explicature of an instruction were it uttered).

But why try to ignore inferences when we can use them?  Humans have enormous power over computers to investigate, learn, observe, interpret, infer, follow up, ask for information. So why write scripts to tell them what to do? If they're powerful enough to investigate a product surely it's cheaper and easier just to train them on how to look for problems rather than explicitly tell them what problems to look for. There is an answer to the above question which I hope to get to in a separate post.

What Is/Is Not A Script (In Testing)?

Things That Are Scripts (In Testing)

Automated Check Scripts

Automated "tests" are a set of instructions (the code) made explict by one agent (coded) such that another agent (the computer/compiler/interpretter) can later interpret (run/compile/interpret) them in order to replicate a process (making many checks quickly and forming some kind of output with the data) to achieve a desired outcome (the results of specific observations of the system in a way that a human can easily interpret, understand and evaluate)

Things That Aren't Scripts (In Testing)


Notes are not usually scripts. Notes are simply anything made explicit for the purposes of later reference. Scripts more specific - they refer to a set of instructions to be later interpreted to achieve a desired behaviour or outcome. Not all notes consist of a set of instructions and not all notes are designed to achieve a desired behaviour or outcome. All scripts are notes. Not all notes are scripts - in fact so few that we can make a abductive leap and say that when someone says "notes" they don't mean "scripts" because if they did they'd likely have said "scripts" to differentiate it from "notes".


A mission or charter is similar to a script in that it contains some explicit information and is used to communicate something in order to achieve a desired outcome or behaviour. The difference is that the communicated information is not a list of instructions to replicate a process. The instructions are not made explicit - the desired outcome or behaviour is. The steps taken (the set of instructions that replicate the process) is left up to the agent. It could be that a mission or charter contains a checklist (a type of script) so missions and charters can use the power of scripts. It may note a list of things that must be tested, information that's especially important, instructions on how to configure the system for the testing, and so on.

So while a recipe is a kind of script a note that says "We need a sponge cake. Plenty of lemon icing, please, and that fancy swirly decoration thing on the top."  is a mission, or charter. The recipe is left up to the chef - or maybe the recipient of the note will go out and buy a cake, or commission a custom cake.

Things That Might Be Scripts (In Testing)


A checklist is simply a list of checks. The problem here is that it depends on how much information is left implicit in that list of checks that will determine if the checklist matches my definition of a script. Remember, a script is "a set of instructions made explicit by one agent such that another (or the same) agent can later interpret them in order to replicate a process to achieve a desired outcome or behaviour". This means that if the checklist has the intention and capacity to replicate a process then it's a script. If the process is left to the agent interpreting the checklist to achieve the desired outcome or behaviour then it's not. I'd go as far to say that most checklists are not scripts.

I'll update the list above as I find more things that are confused with scripts.

Thanks for reading, now please disagree with me!

- Kinofrost

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