Initial documentary for configuration schema

docs/developers/config_schema.md

@@ -0,0 +1,36 @@
+# Configuration Schema
+The configuration schema is a JSON schema, which is for validating the strcuture of sensor data. By running the command `snakemake --list-params-changes`, rapids will check if all settings match the standard without computing the sensor data. The configuration can be divided into three parts: required, definitions and properties. 
+
+### Required
+This part specifies the required features that need to be defined under the properties. If there is any missing feature, it will throw an error message. 
+For example, there is a required feature called `Testing_feature` but it is not defined in the properties. When running `snakemake --list-params-changes`, here is the error message you will see, `ValidationError: 'Testing_feature' is a required property`. 
+
+### Definitions 
+Features might share some common properties, to reuse the structure of the common properties in other places, you can define the property under the definitions, then using `$ref` to refer to the defined property. 
+
+For example, there is a defined property called `PROVIDERS` in `definitions` and a new feature called `phone_messages` has such property. 
+
+![picture](/img/provider_example.png)
+
+To reuse the definiation of `PROVIDERS`, all you need to do is adding `$ref: "#/definitions/PROVIDER"` to the additional property of `phone_messages`.
+
+![picture](/img/phone_messages_example.png)
+
+You can also overwrite the existing property in `PROVIDERS` if the definiation of a certain property is different from the current `PROVIDER`, or extend the properties of `PROVIDERS`.
+
+
+For more examples and details, please refer to http://json-schema.org/understanding-json-schema/structuring.html#reuse
+
+### Properties
+This is where features are defined. The definition of a feature usually contains three things. The type of the feature, a list of required properties, and the definition of each property. A feature is usually an object, which is like the dictionary in Python. Everthing inside the object is a pair, meaning that it has a key and a value. In JSON schema, the `keys` must always be string. Besides object, other common types are string, numeric, array, boolean and null. 
+
+For example,
+
+![picture](/img/feature_example.png)
+
+The sensor feature PHONE_AWARE_LOG is an object with two required properties, `TABLE` and `PROVIDERS`. The `TABLE` contains the name of the data table used for computation, which is a string. The `PROVIDERS` has two types, `null` and `object` meaning that PHONE_AWARE_LOG may or may not have a provider. 
+
+### Refrences
+
+- Understanding JSON Schema: http://json-schema.org/understanding-json-schema/index.html
+- A Media Type for Describing JSON Documents: https://tools.ietf.org/html/draft-handrews-json-schema-01

mkdocs.yml

@@ -30,6 +30,7 @@ markdown_extensions:
     - pymdownx.tilde
     - attr_list
     - pymdownx.keys
+    - def_list
 extra:
   version:
     method: mike
@@ -125,6 +126,7 @@ nav:
     - Documentation: developers/documentation.md
     - Testing: developers/testing.md
     - Test cases: developers/test-cases.md
+    - Configuration Schema: developers/config_schema.md
   - Others:
     - Migrating from beta: migrating-from-old-versions.md
     - Code of Conduct: code_of_conduct.md