Merge branch 'MAS-2018-0084-SDT4_JSON' into 'WI-0081-Smart_Device_Template_4_0'

Mas 2018 0084 sdt4 json

As agreed during TP#36

See merge request !7

.project

+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>SDT</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+	</buildSpec>
+	<natures>
+	</natures>
+</projectDescription>

README.md

@@ -25,6 +25,7 @@ You can find further Information here:
 
 - [Introduction to the SDT](SDT/schema4.0/docs/Introduction.md)
 - [SDT Components](SDT/schema4.0/docs/SDT_Components.md)
+- [JSON Serializatoin](SDT/schema4.0/docs/SDT_JSON.md)
 - [SDT Build System](SDT/schema4.0/docs/SDT%20Build%20System.md)
 - [Examples](SDT/schema4.0/docs/Examples.md) 
 - [Links & References](SDT/schema4.0/docs/Links.md)

SDT/schema4.0/docs/SDT_JSON.md

+When SDT was introduced, XML was the favorite encoding format for schemas. Since then, JSON became more popular in the developers' communities, especially in the context of RESTful implementation. 
+
+JSON is more concise and human-readable comparing to XML, but has less capability of formal schema definition and validation (such as the XML Schema as defined in [domain.xsd](SDT/schema4.0/src/domain.xsd)). 
+
+For these reasons, JSON serialization is supported since SDT4.0.
+
+There are some open tools such as [JSON Schema](http://json-schema.org/) that might be useful for describing and validating the JSON serialization of SDT, but it's not yet a formal standard and is still under development.
+
+In this release, we chose to define the JSON serialization by the documentation below, while borrowing some valuable aspects from JSON Schema (e.g. data types and validation keywords). Full endorsement of [JSON Schema](http://json-schema.org/) may be considered in future.
+
+Some JSON examples can be found in [SDT Components](SDT/schema4.0/docs/SDT_Components.md) and a full exmaple can be found in [JSON Example](SDT/schema4.0/docs/JSON_Example.md)
+
+*Editor's note: a full JSON example will be developed later when the solution is complete*
+
+# SDT Elements mapping to JSON
+
+| SDT Elements | JSON Key Word |
+|--------------|------------|
+| Domain | Domain |
+|Imports (*capitalization is not consistent in XML)|Imports (*FFS)|
+|Doc |Doc |
+|extends (why it's de-capitalized in XML?) |Extends |
+|ImplementedModuleClasses  |ImplementedModuleClasses |
+|ImplementedProperties  |ImplementedProperties  |
+|DeviceClasses | DeviceClasses|
+|SubDevice | SubDevice|
+|Product  | Product|
+|Properties |Properties |
+|ModuleClasses | ModuleClasses|
+|Data| DataPoints|
+|Actions| Actions|
+| Args | Args|
+|Events | Events|
+|DataType|  | DataType|
+
+*Editor's note: In XML schema, data-point is tagged as 'Data'. Should we change it to 'DataPoints' to be consistent?*
+
+# SDT Attributes mapping to JSON
+There are common attributes (e.g. *@id, @name, @optional*) used in several SDT components (e.g. *DeviceClass, ModuleClass*) as well as attributes used only in certain components (e.g. *@class* in *Extends*). The mapping of those attributes to JSON follows the same rule as below.
+
+| SDT Attributes | JSON Key Word |
+|----------------|-------------|
+| @id  |id |
+| @name  |name |
+| @value  |value |
+|  @optional | optional|
+|  @readable | readable|
+|  @writable | writable|
+|  @eventable | eventable|
+| @domain  |domain |
+| @class  |class |
+
+
+
+# SDT data types and constraints mapping to JSON
+*Editor's note: defining standardized SDT data type constraints as listed below in the main spec - SDT_Components.md and domain.xsd is ffs*
+
+| SDT Data Types |  Values | Constrains | JSON Key Word | Note |
+|----------------|-----------|------|------|----|
+|  SimpleType |   || - | For simplicity, the type value of *SimpleType* is directly put as the value of parent *DataType* key, e.g. "DataType":"String".|
+|  |  boolean || boolean | JSON Schema |
+|  |  byte  || byte  | An integer datatype with the range of [0 - 255] |
+|  |  integer | | integer  | JSON Schema |
+|  |   | multipleOf | multipleOf  | JSON Schema |
+|  |   | maximum  | maximum   | JSON Schema |
+|  |   | exclusiveMaximum  | exclusiveMaximum   | JSON Schema |
+|  |   | minimum   | minimum    | JSON Schema |
+|  |   | exclusiveMinimum    | exclusiveMinimum     | JSON Schema |
+|  |  float  || number  | JSON Schema |
+|  |   | multipleOf | multipleOf  | JSON Schema |
+|  |   | maximum  | maximum   | JSON Schema |
+|  |   | exclusiveMaximum  | exclusiveMaximum   | JSON Schema |
+|  |   | minimum   | minimum    | JSON Schema |
+|  |   | exclusiveMinimum    | exclusiveMinimum     | JSON Schema |
+|  |  string  || string  | JSON Schema |
+|  |   | maxLength   | maxLength    | JSON Schema |
+|  |   | minLength   | minLength    | JSON Schema |
+|  |   | pattern   | pattern    | JSON Schema |
+|  |  enum   || enum  | JSON Schema |
+|  |  date    || date   | JSON Schema |
+|  |  time   || time   | JSON Schema |
+|  |  datetime || date-time    | JSON Schema |
+|  |  blob    || blob    | A **base64Binary** encoded string according to [RFC 2045](https://www.w3.org/TR/xmlschema-2/#RFC2045) |
+|  |  uri    || uri    | JSON Schema |
+|  StructType ||   | Struct | |
+|  ArrayType ||   | Array | |
+
+