HTML is a markup language (マークアップ言語) that describes the structure of a web page, such as headings, paragraphs and links, with tags (タグ; markers enclosed in "<" and ">").
To mark up text means to attach labels such as "this is a heading" to its parts to show their roles. A browser reads a file written in HTML and assembles the page on screen according to those labels. When a hyperlink is written in, readers can move from that page to another one.
AnalogyIt is like writing notes such as "main heading" or "photo here" in red in the margins of a manuscript, so the printer lays out the page exactly as marked.
How to rememberHyperText = text that links to other documents; Markup = adding marks. The name itself says "a language for marking up linked documents."
Exam points
ExamWhat HTML lets you build is web pages (Web ページ).
ExamHTML tags (タグ) can do more than show a document's structure; they can also specify how it looks on screen.
A tag (タグ) is a marker that encloses a name in "<" and ">" and shows which stretch of a document or data represents what.
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Content is usually enclosed between a start tag such as <p> and an end tag with a slash added, such as </p>, forming one element. Placing elements inside other elements, called nesting, expresses a hierarchy like sections within a chapter. When a browser displays the page, the tags themselves do not appear on screen; they give a role to the content they enclose.
AnalogyIt is like putting two bookmarks in a book to show "Chapter 2 starts here" and "Chapter 2 ends here". The text does not change, but you can see which stretch is what.
How to rememberIn everyday English, a tag is a name label tied to luggage. Its job of naming what is inside carries straight over to the term.
Exam points
ExamThe logical structure of an XML document is expressed by enclosing each part in tags (タグ).
XML is a markup language (マークアップ言語) in which users name their own tags (タグ) to suit their purpose and describe the meaning and structure of data.
Book
Title
Author
Family name
Given name
Price
Its hallmark is that you can create new tags to fit the information at hand; for book data, for example, you might make tags named book, title, author and price and nest them in a hierarchy. Because the tag names reveal what the content means, XML serves as a format for passing data between different systems.
AnalogyIt is like a storage shelf where you can make your own labels. Just as you might put small "family name" and "given name" boxes inside the "author" shelf, you decide how things are divided.
How to rememberThe X in the abbreviation comes from the second letter of eXtensible. The name uses X rather than the initial E.
Exam points
ExamIn XML, the writer can decide which tags (タグ) to use according to the content of the data.
Mix-upHTML uses tags (タグ) prepared in advance for building web pages, while in XML the users create tags that represent the content of the data.
SGML is an international-standard metalanguage (メタ言語) used to define the markup languages themselves, which structure documents with tags.
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A metalanguage is a language for setting the rules of how another language is written. SGML is a standard that predates HTML and XML, and both were built on it. On today's web, SGML is almost never written directly.
AnalogyIt is like a "guide to designing formats" that exists before any individual format is designed. Formats for each purpose branch off from that guide.
How to rememberStandard Generalized = standard and general-purpose. The name carries the idea of a root standard that comes before narrowing to any particular use.
JSON is a lightweight data description format that uses no tags and represents data mainly as pairs of a key (item name) and a value enclosed in curly braces.
For example, in {"product": "notebook", "stock": 42}, a colon joins each key to its value and commas separate the pairs. It grew out of the way JavaScript writes objects, but today it is widely used for exchanging data between web services regardless of programming language.
How to rememberJavaScript Object Notation = the way JavaScript writes objects. Its origin is right there in the name.