Add YAML metadata guideline

CONTRIBUTING.md

@@ -8,6 +8,7 @@ The document covers the process for contributing to the articles and code sample
     1. [Repository structure](#repository-structure)
     1. [File Name](#file-name)
     1. [Naming Rules for Tizen Terms](./styleguide/naming-rules.md)
+    1. [YAML metadata in Tizen documentents](./styleguide/yaml-metadata.md)
 1.  [DOs and DON'Ts](#dos-and-donts)
 1.  [Content license](#content-license)
 1.  [Contributor License Agreement](#contributor-license-agreement)

styleguide/yaml-metadata.md

@@ -0,0 +1,104 @@
+# YAML metadata in Tizen documentents
+
+This guideline describes YAML syntax and YAML meta.
+
+The following code shows the YAML metadata in Tizen documents.
+
+## Syntax
+
+All YAML files can optionally begin with `---` and end with `---`. This is part of the YAML format and indicates the start and end of a document.
+
+
+A dictionary is represented in a simple `key: value` form (the colon must be followed by a space):
+```
+---
+title: YAML metadata in Tizen documentents
+author: Anonymous (anonymous@tizen.org)
+summary: YAML metadata guideline
+keyword: YAML, metadata, Tizen, YAML syntax
+redirect: overview
+---
+```
+
+## YAML elements
+
+The Tizen documentation has various YAML elements.
+
+### title 
+
+There is no title in menu, the title in meta displays displays this title.
+
+```
+---
+title: YAML metadata in Tizen documentents
+---
+```
+
+### author
+
+The Tizen repository is in public GitHub so we don't know the exact the document authors.
+When the authors are listed, it helps to contact the authors when there are issues.
+
+```
+---
+author: Anonymous (anonymous@tizen.org)
+---
+```
+
+### summary
+
+Summary describes what the document is briefly. 
+
+```
+---
+summary: YAML metadata guideline
+---
+```
+
+### keyword
+
+Keywords in the document are extracted automatically when a Pull Request is sent. The extracted keywords are words list. Words are split by a space. In other words, it can't detect collocations with space such as "heavy rain", "high temperature", and "have an experience".
+However, you can manually insert keywords at the beginning of documents to improve Search Engine Optimization (SEO).
+
+```
+---
+keyword: Tizen, guidleline, YAML syntax
+---
+```
+In the above example, "YAML syntax" is a kind of collocations.
+
+### redirect
+
+Redirect allows the page jump the other page. For example, there is a representative page, which is a root having lots of children. 
+In general, when there is `index.md` in the root directory, and children in subdirectories.
+
+For example, Your  documents exist in folders as the follows:
+```
+root
+├── build
+│   └── package.md
+├── index.md
+└── setup
+    └── overview.md
+    └── install.md
+
+```
+
+You want to show the overview page, as soon as a user click the root page. In this case, `index.md` has only YAML metadata.
+
+The following YAML meta can fulfill your requirement.
+
+```
+---
+redirect: setup/overview
+---
+```
+
+### 
+
+## Related information
+
+- [YAML](https://yaml.org/)
+- [YAML Syntax](https://docs.ansible.com/ansible/latest/reference_appendices/YAMLSyntax.html)
+- [Metadata in Microsoft Word documents](https://blog.martinfenner.org/2015/03/20/metadata-in-microsoft-word-documents/)
+