science

Hypertext Application Language

Hypertext Application Language 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 Hypertext Application Language rather than just read about it. In short: Hypertext Application Language (HAL) is a convention for defining hypermedia such as links to external resources within JSON or XML code. It is documented in an Internet Draft (a "work in progress"), with the latest version 11 published 10 October 2023.

Key takeaways

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

Reference excerpt

Hypertext Application Language (HAL) is a convention for defining hypermedia such as links to external resources within JSON or XML code. It is documented in an Internet Draft (a "work in progress"), with the latest version 11 published 10 October 2023. The standard was initially proposed in June 2012, specifically for use with JSON, and has since become available in two variations, JSON and XML. The two associated MIME types are application/hal+xml and application/hal+json. HAL was created to be simple to use and easily applicable across different domains by avoiding the need to impose any requirements on how the project be structured. Maintaining this minimal impact approach, HAL has enabled developers to create general-purpose libraries which can be incorporated on any API that uses HAL. APIs that adopt HAL simplify the use of open source libraries and make it possible to interact with the API using JSON or XML. The alternative would be having to develop a proprietary format which in turn forces developers to learn how to use yet another foreign format.

Convention HAL is structured in such a way as to represent elements based on two concepts: Resources and Links. Resources consist of URI links, embedded resources, your standard data (be it JSON or XML), and non URI links. Links have a target URI, as well as the name of the link (referred to as 'rel'), as well as optional properties designed to be mindful of deprecation and content negotiation.

Example General Resource

Embedded resource

Collections

See also HATEOAS CURIE, (or Compact URI)

References

External links JSON Hypertext Application Language latest draft

Worked examples

Example 1 — a first encounter with Hypertext Application Language

Start with the simplest possible case. Write down what Hypertext Application Language 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 Hypertext Application Language 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 Hypertext Application Language 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 Hypertext Application Language

In research: Hypertext Application Language 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 Hypertext Application Language 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: Hypertext Application Language is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data serialization formats, JSON, Markup languages, so understanding it makes those chapters shorter.
In everyday life: Look for Hypertext Application Language 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 Hypertext Application Language in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hypertext Application Language 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 Hypertext Application Language out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hypertext Application Language in simple terms?

Why does Hypertext Application Language 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 Hypertext Application Language?

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 Hypertext Application Language.