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+# 5 Levels of data reusability
+
+Not all data are created equal.
+There are notable differences in how much you can do with data and how much effort it takes.
+The more reusable data is, the easier it will be to use it as a developer, researcher or other type of data user.
+Re-useability is about being able to transform, sort, query, serialize,  modify, render and audit data without requiring too much work.
+
+_This list is inspired by Tim Berners-Lee's [5-star open data](https://5stardata.info/en/)_.
+
+## Level 0: proprietary data
+
+If you don't give others the _rights_ to read, use or modify your data, it's reusability is zero.
+
+That's why it's important to have a _license_ that allow others to use your data, like the [Open Database License](https://opendatacommons.org/licenses/odbl/summary/).
+or one of the Creative Commons licenses.
+
+It's also important to use _open formats_ (such as `CSV`, `JSON` or `PNG`), instead of _proprietary formats_ (tied to specific vendors, such as `PSD` or `RAR`).
+
+
+## Level 1: unstructured data
+
+_Examples: images, videos, plain text_
+
+Unstructured data is the least usable.
+Humans can read it, and AI / Machine Learning systems can draw more conclusions from it then ever,
+but it's hard to build an actual application or graphic from only unstructured data.
+
+```
+Hi! I'm Joep, I'm born in 1991.
+```
+
+## Level 2: structured data
+
+_Examples: CSV, XML, JSON, TOML, EXCEL_
+
+Structured data can be read by machines, and this allows us to do all sorts of useful things.
+We can _query_, _sort_ and _filter_.
+But still, this type of data often requires human input when it needs to be processed.
+And we don't have guarantees about which fields will be filled, or what their datatypes are.
+One time, a `birthYear` can be a string, and the next time it can be a number.
+Data can be _structured_, but still _unpredictable_.
+
+```json
+{
+  "name": "Joep",
+  "birthYear": 1991
+}
+```
+
+If we want predictability, we need to make it _type-safe_.
+
+## Level 3: type-safe data
+
+_Examples: SQL + DB SCHEMA, JSON + JSON schema, XSD + XML, RDF + SHACL, In-memory data in type-safe programming languages_
+
+Type-safe data means that every value of the data has an explicit datatype.
+It is _strongly typed_ and has a clear _schema_ that describes which properties you can expect in a Resource.
+This means that someone re-using type-safe data can know for certain that it conforms to a specification, a set of rules.
+The shape of the data is _predictable_.
+This predictability means that developers can safely re-use it in their system without worrying about missing fields or datatype errors.
+
+Lots of software has _internal_ type safety, especially if you use type-safe programming languages like Typescript, Kotlin or Rust.
+However, when the data _leaves the system_, a lot of type related data is lost.
+Even if this schema related information is described, the schema itself is often not machine-readable.
+The best way to have type-safe data, is to describe the schema in a machine-readable format.
+
+In SQL, we can use a DB schema. In JSON, we can add a JSON Schema file. For XML, we have XSD.
+
+In Atomic Data, the Properties themselves (the links in the keys in JSON-AD) describe the required datatypes, which helps developers when re-using data understand what they can expect from a value.
+
+```json
+{
+  "https://atomicdata.dev/properties/isA": ["https://atomicdata.dev/classes/Agent"],
+  "https://atomicdata.dev/properties/name": "Joep",
+  "https://atomicdata.dev/properties/birthYear": 1991,
+  "https://atomicdata.dev/properties/worksOn": "Atomic Data",
+}
+```
+
+## Level 4: browsable data
+
+_Examples: Atomic Data, properly hosted RDF_
+
+If your data is _connected_ to other pieces of machine-readable dat, is becomes browsable, similar to how websites link to each other.
+This effectively creates a _web of data_, and allows for a whole new way to think about the internet.
+This is what allows decentralized applications, true data ownership, and a new set of applications.
+
+```json
+{
+  "https://atomicdata.dev/properties/isA": ["https://atomicdata.dev/classes/Agent"],
+  "https://atomicdata.dev/properties/name": "Joep",
+  "https://atomicdata.dev/properties/birthYear": 1991,
+  "https://atomicdata.dev/properties/worksOn": "https://atomicdata.dev",
+}
+```
+
+## Level 5: verifiable data
+
+_Examples: Atomic Data + Atomic Commits_
+
+When your data is _verifiable_, other people can verify who created it and modified it.
+They can use cryptography to validate signatures, which proves that one person or machine created a piece of data.
+
+```json
+{
+  "https://atomicdata.dev/properties/isA": ["https://atomicdata.dev/classes/Agent"],
+  "https://atomicdata.dev/properties/name": "Joep",
+  "https://atomicdata.dev/properties/birthYear": 1991,
+  "https://atomicdata.dev/properties/worksOn": "https://atomicdata.dev",
+  "https://atomicdata.dev/properties/previousCommit": "https://atomicdata.dev/commits/EF18751AE781",
+}
+```