diff --git a/Gemfile b/Gemfile
index 02e01cb..cf65dc8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,5 @@
 source "https://rubygems.org"
 
 gem "jekyll", "~> 4.1"
-gem "jekyll-environment-variables"
\ No newline at end of file
+gem "jekyll-environment-variables"
+gem 'jemoji'
diff --git a/_config.yml b/_config.yml
index 353d565..b071efc 100755
--- a/_config.yml
+++ b/_config.yml
@@ -36,3 +36,4 @@ sass:
 
 plugins:
   - jekyll-environment-variables
+  - jemoji
diff --git a/_services/concept.md b/_services/concept.md
new file mode 100644
index 0000000..78291c5
--- /dev/null
+++ b/_services/concept.md
@@ -0,0 +1,64 @@
+---
+title: "CyCAT - Core Concept"
+date: 2021-02-19T01:33:46+10:00
+featured: true
+weight: 1
+layout: service
+---
+
+# Concept of CyCAT url
+
+A CyCAT url is composed of a publisher short name, a project short name and the associated UUID of the specific item. An item can be any part of the collection produced
+by this publisher under a specific project. The CyCAT url is composed of two namespaces separated by colon and a final UUID appended after a colon. The CyCAT url is in UTF-8 format.
+
+`publisher-short-name`:`project-short-name`:`UUID`
+
+## What is an UUID?
+
+A [universally unique identifier (UUID)](https://en.wikipedia.org/wiki/Universally_unique_identifier) is a 128-bit number used to identify information in computer systems also known as GUID.
+CyCAT use such UUID to reference items produced in a collection. CyCAT, by default, will use any existing UUID already assigned by the publisher. If not present or there is no item present,
+a fixed value is then calculated from the UUID namespace of CyCAT combined with `publisher-short-name:project-short-name`.
+
+## Publisher namespace
+
+A publisher can be any organisation, project or individual requesting a publisher to CyCAT.
+
+| Field name        |  Description           | Required  |
+| ------------- |:---------------------------| ---------:|
+| `name` | Name of the publisher (full name)| :heavy_check_mark: |
+| `short-name` | Name of the publisher (short name) | :heavy_check_mark: |
+| `description` | Description of the publisher | :heavy_check_mark: |
+| `cycat-oid` | assigned CyCAT OID | :heavy_check_mark: |
+| `link` | Internet link referencing the publisher | :heavy_check_mark: |
+| `timestamp` | Last update of the publisher record (unix timestamp) | :heavy_check_mark: |
+| `maintainer` | owner, external, cycat | - |
+
+Publisher examples: `mitre`, `circl`, `misp`
+
+## Project namespace
+
+A publisher can request one or more project to CyCAT associated to the publisher namespace.
+
+| Field name        |  Description           | Required  |
+| ------------- |:---------------------------| ---------:|
+| `name` | Name of the project (full name)| :heavy_check_mark: |
+| `short-name` | Name of the project (short name) | :heavy_check_mark: |
+| `description` | Description of the project | :heavy_check_mark: |
+| `cycat-oid` | assigned CyCAT OID | :heavy_check_mark: |
+| `link` | Internet link referencing the project | :heavy_check_mark: |
+| `license` | License(s) of the project in SPX identifier (array) | :heavy_check_mark: |
+| `type` | [Taxonomy type](https://github.com/CyCat-project/cycat-taxonomy) of the project from CyCAT taxonomy | :heavy_check_mark: |
+| `scope` | [Taxonomy scope](https://github.com/CyCat-project/cycat-taxonomy) of the project from CyCAT taxonomy | :heavy_check_mark: |
+| `timestamp` | Last update of the project record  (unix timestamp)| :heavy_check_mark: |
+| `maintainer` | owner, external, cycat | - |
+
+## URL example
+
+## How to generate a CyCAT url for non-registered url or missing item in a collection
+
+CyCAT has a fixed UUID namespace `690b3b43-d689-481c-aa61-5351963a36f2`.
+
+```shell
+% uuidgen --sha1 -n "690b3b43-d689-481c-aa61-5351963a36f2" -N "samratashok:nishang:"
+2605ff5e-342c-5326-8744-96a34b7e581e
+```
diff --git a/services.md b/services.md
index 367812f..1b544cb 100644
--- a/services.md
+++ b/services.md
@@ -10,4 +10,4 @@ intro_image_hide_on_mobile: false
 
 CyCAT will provide a public catalogue including an open API. The alpha version of the system is planned to be launched during the next EU ATT&CK Community workshop, on 1 June 2021.
 
-We are currently in the initial feedback and peer review phase of the [White Paper](services/whitepaper/) and the [draft taxonomy](https://github.com/CyCat-project/cycat-taxonomy) behind the concept. This phase will end on 31 March 2021 and then we'll set out to build the aforementioned alpha version.
+We are currently in the initial feedback and peer review phase of the [White Paper](whitepaper/) and the [draft taxonomy](https://github.com/CyCat-project/cycat-taxonomy) behind the concept. This phase will end on 31 March 2021 and then we'll set out to build the aforementioned alpha version.