# Resources & Images

The term resource describes any media or data that is included within a KDF document. Resources may be images, fonts, videos, scripts, or even plain data. Resources may be stored within the document file under the resources/ directory, or may link to online content.

# What are URIs?

KDF uses Universal Resource Identifiers (URIs) to locate resources, both online and embedded within the document. As such, there are two main use cases we need to cover.

Online resources: In which the URL/URI of the content may be used as is. This is generally not recommended as the document editor or viewer must fetch the resource before it can be used within the document.
```
{
  "image": "http://www.example.com/heading.png"
}
```
Embedded resources: In which a relative URI is used with the following form: resource://<resource-path>. Imagine the resources/ directory contained the following files:
```
resources/images/
  aardvark.png
  arctic-fox.png
  cane-toad.jpg
  toucan.png
```
To create a URI which points to arctic-fox.png, the following URI should be constructed: resource://images/arctic-fox.png.

# Hashing Embedded Resource Names

To help prevent potential problems arising when embedding many similar resources, applications should always rename resources to a hash of their content. The standard hashing algorithm for performing this task is SHA256. This ensures that there will be no resource duplication, and may help with versioning documents in future.

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