science

Progol

Progol is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Progol rather than just read about it. In short: Progol is an implementation of inductive logic programming that combines inverse entailment with general-to-specific search through a refinement graph. Features Inverse entailment is used with mode declarations to derive the bottom clause, the most-specific clause within the mode language which subsume a given example.

Key takeaways

Progol belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Progol to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Progol from memory before moving on to harder problems.

Reference excerpt

Progol is an implementation of inductive logic programming that combines inverse entailment with general-to-specific search through a refinement graph.

Features Inverse entailment is used with mode declarations to derive the bottom clause, the most-specific clause within the mode language which subsume a given example. This clause is used to guide a refinement-graph search. Unlike the searches of Ehud Shapiro's model inference system (MIS) and J. Ross Quinlan's FOIL, Progol's search has a provable guarantee of returning a solution having the maximum compression in the search-space. To do so it performs an admissible A*-like search, guided by compression, over clauses which subsume the most specific clause. Progol deals with noisy data by using a compression measure to trade off the description of errors against the hypothesis description length. Progol allows arbitrary Prolog programs as background knowledge and arbitrary definite clauses as examples.

History Progol was introduced by Stephen Muggleton in 1995. In 1996, it was used by Ashwin Srinivasan, Muggleton, Michael Sternberg and Ross King to predict the mutagenic activity in nitroaromatic compounds. This was considered a landmark application for inductive logic programming, as a general purpose inductive learner had discovered results that were both novel and meaningful to domain experts. Progol proved very influential in the field, and the widely-used inductive logic programming system Aleph builds directly on Progol.

References

Worked examples

Example 1 — a first encounter with Progol

Start with the simplest possible case. Write down what Progol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Progol before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Progol ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Progol

In research: Progol appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Progol in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Progol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Inductive logic programming, so understanding it makes those chapters shorter.
In everyday life: Look for Progol outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Progol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Progol means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Progol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Progol in simple terms?

Progol is an implementation of inductive logic programming that combines inverse entailment with general-to-specific search through a refinement graph. Features Inverse entailment is used with mode declarations to derive the bottom clause, the most-specific clause within the mode language which sub…

Why does Progol matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Progol?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Progol.