Documentation for new JSON as Fact feature (#151)

* Added documentation on JSON as Fact feature

CHANGELOG.md

@@ -103,4 +103,46 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 #### Removed
 
-- Grule Event Bus is removed from Grule as it seems too complicated and no one use them. They just expect grule to just works. 
+- Grule Event Bus is removed from Grule as it seems too complicated and no one use them. They just expect grule to just works.
+
+### [1.7.0] - 2020-11-06
+
+#### Changes
+
+- Change the Grule ANTLR4 grammar for better structure, tested with ANTLR4 hierarchy and AST Tree.
+- FunctionCall AST graph is now under ExpressionAtom instead of Variable
+
+#### Fix
+
+- Proper Integer and Float literals both support exponent format
+
+#### Added
+
+- Integer literal support Octal and Hexadecimal, Float literal support Hexadecimal.
+- Added more documentation about the new numbering literals and also re-arrange the menu in the documentation.
+- Support negation.
+
+### [1.7.1] - 2020-12-02
+
+##### Fix
+
+- Fixed ANTLR4 grammar to enable function chaining in the THEN scope
+- Fixed ANTLR4 grammar error that makes array/slice/map cannot be chained with function
+
+#### Change
+
+- Built-in function `Changed` is renamed to `Forget` to clearly tell the engine to forget about variable values or function invocation to make sure the engine look again into the underlying data context on the next cycle.
+
+### [1.7.2] - 2020-12-09
+
+##### Fix
+
+- Fixes the cloning problem where Expression do not clone the negation attribute
+- Added mutex for unique.NewID() to make sure that this function is thread/concurrent safe.
+
+### [1.8.0] - 2020-12-19
+
+#### Added
+
+- Support for JSON as Fact
+- Support native type variable to be added straight into `DataContext` not only `struct`

docs/JSON_Fact_en.md

@@ -0,0 +1,270 @@
+# JSON Fact
+
+[Tutorial](Tutorial_en.md) | [Rule Engine](RuleEngine_en.md) | [GRL](GRL_en.md) | [GRL JSON](GRL_JSON_en.md) | [RETE Algorithm](RETE_en.md) | [Functions](Function_en.md) | [FAQ](FAQ_en.md) | [Benchmark](Benchmarking_en.md)
+
+---
+
+Using JSON straight away as fact in Grule is available starting on version 1.8.0. It enable user to treat JSON string as fact
+and add it into `DataContext` just like how you previously add fact data into it. The loaded JSON fact are now "visible" the
+the Grule scripts (the GRLs).
+
+## Adding JSON as fact
+
+Assuming you have a JSON as follow:
+
+```json
+{
+  "name" : "John Doe",
+  "age" : 24,
+  "gender" : "M",
+  "height" : 74.8,
+  "married" : false,
+  "address" : {
+    "street" : "9886 2nd St.",
+    "city" : "Carpentersville",
+    "state" : "Illinois",
+    "postal" : 60110
+  },
+  "friends" : [ "Roth", "Jane", "Jake" ]
+}
+```
+
+You put your JSON into a byte array.
+
+```go
+myJSON := []byte (...your JSON here...)
+```
+
+You simply add you JSON variable into `DataContext`
+
+```go
+// create new instance of DataContext
+dataContext := ast.NewDataContext()
+
+// add your JSON Fact into data cotnxt using AddJSON() function.
+err := dataContext.AddJSON("MyJSON", myJSON)
+```
+
+Yes, you can add as many _facts_ as you wish into the context and you can mix between JSON facts
+(using `AddJSON`) and normal Go fact (using `Add`)
+
+ ## Evaluating (Reading) JSON Fact Values in GRL
+
+ Inside GRL script, the fact is always visible through their label as you provide them 
+ when adding to the `DataContext`. For example, the code bellow add your JSON and it will be 
+ using label `MyJSON`.
+
+ ```go
+err := dataContext.AddJSON("MyJSON", myJSON)
+```
+
+ Yes, you can use any label as long as its a single word.
+
+ ### Traversing member variable like a normal object
+
+ Now. Using the JSON shown at the beginning, your GRL `when` scope can evaluate your json 
+ like the following.
+
+ ```text
+when
+    MyJSON.name == "John Doe"
+``` 
+
+or 
+
+```text
+when
+    MyJSON.address.city.StrContains("ville")
+```
+
+or
+
+```text
+when
+    MyJSON.age > 30 && MyJSON.height < 60
+```
+
+### Traversing member variable like a map
+
+You can access JSON object's fields using `Map` like selector or like normal object.
+
+ ```text
+when
+    MyJSON["name"] == "John Doe"
+``` 
+
+or 
+
+```text
+when
+    MyJSON["address"].city.StrContains("ville")
+```
+
+or
+
+```text
+when
+    MyJSON.age > 30 && MyJSON["HEIGHT".ToLower()] < 60
+```
+
+### Traversing array member variable
+
+You can inspect JSON Array element just like a normal array
+
+ ```text
+when
+    MyJSON.friends[3] == "Jake"
+```
+
+## Writing values into JSON Facts in GRL
+
+Yes, you can write new values into you JSON facts in the `then` scope of your rules. Changing those values will
+certainly evaluated on the following rule evaluation cycles. BUT, there are some caveat (read "Things you should know" bellow.)
+
+### Writing member variable like a normal object
+
+Now. Using the JSON shown at the beginning, your GRL `then` scope can modify your json 
+**fact** like the following.
+
+ ```text
+then
+    MyJSON.name = "Robert Woo";
+``` 
+
+or 
+
+```text
+then
+    MyJSON.address.city = "Corruscant";
+```
+
+or
+
+```text
+then
+    MyJSON.age = 30;
+```
+
+That's pretty straight forward. But there are some twist to this.
+
+1. You can modify not only the value of member variable of your JSON object, you can also change the `type`.
+   Assuming your rule can handle the next evaluation chain for the new type you can do this, otherwise we very strongly not recommended this.
+
+   Example:
+
+   You modify the `MyJSON.age` into string.
+
+   ```text
+    then
+        MyJSON.age = "Thirty";
+   ```
+
+   This make the engine to panic when evaluating rule like.
+
+   ```text
+    when
+        myJSON.age > 25
+   ```
+
+2. You can assign a value to non-existent member variable
+
+   Example:
+
+      ```text
+       then
+           MyJSON.category = "FAT";
+      ```
+
+    Where the `category` member is not existed in the original JSON.
+    
+### Writing member variable like a normal map
+ 
+Now. Using the JSON shown at the beginning, your GRL `then` scope can modify your json 
+**fact** like the following.
+ 
+ ```text
+then
+    MyJSON["name"] = "Robert Woo";
+``` 
+
+or 
+
+```text
+then
+    MyJSON["address"]["city"] = "Corruscant";
+```
+
+or
+
+```text
+then
+    MyJSON["age"] = 30;
+```
+
+Like the object style, there are same exact twist to this.
+
+1. You can modify not only the value of member variable of your JSON map, you can also change the `type`.
+   Assuming your rule can handle the next evaluation chain for the new type you can do this, otherwise we very strongly not recommended this.
+
+   Example:
+
+   You modify the `MyJSON.age` into string.
+
+   ```text
+    then
+        MyJSON["age"] = "Thirty";
+   ```
+
+   This make the engine to panic when evaluating rule like.
+
+   ```text
+    when
+        myJSON.age > 25
+   ```
+
+2. You can assign a value to non-existent member variable
+
+   Example:
+
+      ```text
+       then
+           MyJSON["category"] = "FAT";
+      ```
+
+    Where the `category` member is not existed in the original JSON.
+
+### Writing member array
+
+In array you can simple replace array element by it's indices.
+
+```text
+then
+   MyJSON.friends[3] == "Jake";
+```
+
+As long as that indice is a valid one. Grule will panic if the indices is out of bound.
+Just like normal JSON, you can replace the value of any element with different type.
+You can always inspect the array length. Like ...
+
+```text
+when
+   MyJSON.friends.Length() > 4;
+```
+
+Yes, you can always append into Array using `Append` function. Append list of argument value of different types.
+
+```text
+then
+   MyJSON.friends.Append("Rubby", "Anderson", "Smith", 12.3);
+```
+
+**Known Issue**
+
+As of now, there are no built-in function to help user to inspect array element easily, such as `Contains(value) bool`
+
+## Things you should know
+
+1. After you add JSON fact into `DataContext`, the change to this string variable will not reflect the facts already in the `DataContext`. This is also
+   applied in vice-versa, where changes in the fact within `DataContext` will not change the JSON string.
+2. You can modify your JSON fact in the `then` scope, but unlike normal `Go` facts, these changes will not reflect to your original JSON string. If you want this to happen, 
+   you should parse your JSON into a `struct` before hand, and add your `struct` into `DataContext` normally. 

docs/Tutorial_en.md

@@ -88,6 +88,11 @@ if err != nil {
 }
 ```
 
+### Add JSON as Fact
+
+JSON string as a fact in Grule is a feature introduced at version 1.8.0. 
+You can read [JSON as a Fact](JSON_Fact_en.md) to know how to add JSON into `DataContext`.
+
 ## Creating KnowledgeLibrary and Add Rules Into It
 
 A `KnowledgeLibrary` is basically collection of `KnowledgeBase` blue prints.