Question

I have heard of the concept of minimizing code and maximizing data, and was wondering what advice other people can give me on how/why I should do this when building my own systems?

Answer 1

In modern software the line between code and data can become awfully thin and blurry, and it is not always easy to tell the two apart. After all, as far as the computer is concerned, everything is data, unless it is determined by existing code – normally the OS – to be otherwise. Even programs have to be loaded into memory as data, before the CPU can execute them.

For example, imagine an algorithm that computes the cost of an order, where larger orders get lower prices per item. It is part of a larger software system in a store, written in C.

This algorithm is written in C and reads a file that contains an input table provided by the management with the various per-item prices and the corresponding order size thresholds. Most people would argue that a file with a simple input table is, of course, data.

Now, imagine that the store changes its policy to some sort of asymptotic function, rather than pre-selected thresholds, so that it can accommodate insanely large orders. They might also want to factor in exchange rates and inflation – or whatever else the management people come up with.

The store hires a competent programmer and she embeds a nice mathematical expression parser in the original C code. The input file now contains an expression with global variables, functions such as log() and tan(), as well as some simple stuff like the Planck constant and the rate of carbon-14 degradation.

cost = (base * ordered * exchange * ... + ... / ...)^13

Most people would still argue that the expression, even if not as simple as a table, is in fact data. After all it is probably provided as-is by the management.

The store receives a large amount of complaints from clients that became brain-dead trying to estimate their expenses and from the accounting people about the large amount of loose change. The store decides to go back to the table for small orders and use a Fibonacci sequence for larger orders.

The programmer gets tired of modifying and recompiling the C code, so she embeds a Python interpretter instead. The input file now contains a Python function that polls a roomfull of Fib(n) monkeys for the cost of large orders.

Question: Is this input file data?

From a strict technical point, there is nothing different. Both the table and the expression needed to be parsed before usage. The mathematical expression parser probably supported branching and functions – it might not have been Turing-complete, but it still used a language of its own (e.g. MathML).

Yet now many people would argue that the input file just became code.

So what is the distinguishing feature that turns the input format from data into code?

• Modifiability: Having to recompile the whole system to effect a change is a very good indication of a code-centric system. Yet I can easily imagine (well, more like I have actually seen) software that has been designed incompetently enough to have e.g. an input table built-in at compile time. And let’s not forget that many applications still have icons – that most people would deem data – built in their executables.

• Input format: This is the – in my opinion, naively – most common factor that people consider: “If it is in a programming language then it is code”. Fine, C is code – you have to compile it after all. I would also agree that Python is also code – it is a full blown language. So why isn’t XML/XSL code? XSL is a quite complex language in its own right – hence the L in its name.

In my opinion, none of these two criteria is the actual distinguishing feature. I think that people should consider something else:

• Maintainability: In short, if the user of the system has to hire a third party to make the expertise needed to modify the behaviour of the system available, then the system should be considered code-centric to a degree.

This, of course, means that whether a system is data-driven or not should be considered at least in relation to the target audience – if not in relation to the client on a case-by-case basis.

It also means that the distinction can be impacted by the available toolset. The UML specification is a nightmare to go through, but these days we have all those graphical UML editors to help us. If there was some kind of third-party high-level AI tool that parses natural language and produces XML/Python/whatever, then the system becomes data-driven even for far more complex input.

A small store probably does not have the expertise or the resources to hire a third party. So, something that allows the workers to modify its behaviour with the knowledge that one would get in an average management course – mathematics, charts etc – could be considered sufficiently data-driven for this audience.

On the other hand, a multi-billion international corporation usually has in its payroll a bunch of IT specialists and Web designers. Therefore, XML/XSL, Javascript, or even Python and PHP are probably easy enough for it to handle. It also has complex enough requirements that something simpler might just not cut it.

I believe that when designing a software system, one should strive to achieve that fine balance in the used input formats where the target audience can do what they need to, without having to frequently call on third parties.

It should be noted that outsourcing blurs the lines even more. There are quite a few issues, for which the current technology simply does not allow the solution to be approachable by the layman. In that case the target audience of the solution should probably be considered to be the third party to which the operation would be outsourced to.
That third party can be expected to employ a fair number of experts.