Understanding the Core concepts of Atomic Data are fundamental for reading the rest of the documentation.
Atomic Data is a data model for sharing information on the web. It is a directed, labeled graph, similar to RDF. It can be used to express any type of information, including personal data, vocabularies, metadata, documents, files and more. Contrary to some other (labeled) graph data models, a relationship between two items (Resources) does not have attributes. It's designed to be easily serializable to both JSON and linked data formats.
The smallest possible piece of meaningful data / information. You can think of an Atom as a single cell in a spreadsheet or database. An Atom consists of three fields:
- Subject: the Thing that the atom is providing information about.
- Property: the property of the Thing that the atom is about (will always be a URL to a Property).
- Value: the new piece of information about the Atom.
If you're familiar with RDF, you'll notice similarities. An Atom is comparable with an RDF Triple / Statement (although there are important differences).
Let's turn this sentence into Atoms:
Arnold Peters, who's born on the 20th of Januari 1991, has a best friend named Britta Smalls.
The table above shows easily readable strings, but in reality, Atomic Data will almost exclusively consist of links (URLs). The standard serialization format for Atomic Data is AD3, which looks like this:
["https://example.com/arnold","https://example.com/properties/lastname","Peters"] ["https://example.com/arnold","https://example.com/properties/birthDate","1991-01-20"] ["https://example.com/arnold","https://example.com/properties/bestFriend","https://example.com/britta"] ["https://example.com/britta","https://example.com/properties/lastname","Smalls"]
In the Atomic Data above, we have:
- four different Atoms (every line is an Atom)
- two different Subjects:
- three different Properties (
- four different Values (
All Subjects and Properties are Atomic URLs: they are links that point to more Atomic Data.
One of the Values is a URL, too, but we also have values like
These Values have different Datatypes
In most other data formats, the datatypes are limited and are visually distinct.
JSON, for example, has
In Atomic Data, however, datatypes are defined somewhere else, and are extendible.
To find the Datatype of an Atom, you fetch the Property, and that one has a Datatype.
For example, the
https://example.com/properties/bornAt Property requires an ISO Date string, and the
https://example.com/properties/firstName Property requires a regular string.
This might seem a little tedious and weird at first, but is has some nice advantages!
Their Datatypes are defined in the Properties.
The Subject field is the first part of an Atom. It is the identifier that the rest of the Atom is providing information about. The Subject field is a URL that points to the Resource. The creator of the Subject MUST make sure that it resolves. In other words: following / downloading the Subject link will provide you with all the Atoms about the Subject (see Atomic Querying. This also means that the creator of a Resource must make sure that it is available at its URL - probably by hosting the data, or by using some service that hosts it.
The Property field is the second part of an Atom.
It is a URL that points to an Atomic Property.
The Property field MUST be a URL, and that URL MUST resolve to an Atomic Property, which contains information about the Datatype.
The Value field is the third part of an Atom.
In RDF, this is called an
Contrary to the Subject and Property values, the Value can be of any datatype.
This includes URLs, strings, integers, dates and more.
A Graph is a set of Atoms. A Graph can describe various subjects, and may or may not be related. Graphs can have several characteristics (Schema Complete, Valid, Closed)
A Resource is a set of Atoms (a Graph) that share the same Subject URL.
You can think of a Resource as a single row in a spreadsheet or database.
In practice, Resources can be anything - a Person, a Blogpost, a Todo item.
A Resource consists of at least one Atom, so it always has some Property and some Value.
The most important Property of a Resource is the
isa Property, which refers to which Class it belongs (e.g. Person or Blogpost).
A Class can specify required and recommended properties.
More on that in the Atomic Schema chapter!
The Atomic Web refers to all Atomic Graphs on the web.