Functional requirement

VSS item

GraphQL correspondance

•  Model can be specified in multiple files.

Include

• It is possible to specify schema across multiple files.
• Command Line tool has to include all files/links.

•  Human-friendly context is provided.

Concatenated path

• docs/_TYPE
• Hierarchy outside GraphQL (context, field...)

•  Properties can be grouped. Hierarchical concept scheme to group properties belonging to the same area of interest is supported.

Branch type

Aggregate

Struct

• type based
• grouping is implicit

•  Properties whose values do not change often can be specified.

Attribute type

• A field is specified.

•  Properties whose value might change often can be specified as observable or actuatable.

Sensor type

Actuator type

• A field is specified. The associated value is assigned with the instance data

•  Definitions can be reused when there are multiple occurrences.

Instances

• It is possible to specify that a field can have multiple instances. 

  enum CarDoorPosition {
    FRONT_L
    FRONT_R
    REAR_L
    REAR_R
  }
  
  type Car {
    id: ID!
    make: String!
    model: String!
    doors: [CarDoor!]!
  }
  
  type CarDoor {
    id: ID!
    position: CarDoorPosition!
  }

•  Arrays or lists are supported.

Arrays (i.e., datatype[])

• supported by the language with [ ]
  

  type Vehicle {
    id: ID!
    make: String!
    model: String!
    doors: [String!]!
  }

•  Extended list of primitive datatypes is supported.

(u)intX, boolean, float, double, string

• Custom scalars can be defined as an extension. In the GraphQL schema we might have something like:
  

  scalar Int8 @specifiedBy(url: "xsd:byte")
  scalar UInt8 @specifiedBy(url: "xsd:unsignedByte")
  scalar Int16 @specifiedBy(url: "xsd:short")
  scalar UInt16 @specifiedBy(url: "xsd:unsignedShort")
  scalar UInt32 @specifiedBy(url: "xsd:unsignedInt")
  scalar Int64 @specifiedBy(url: "xsd:long")
  scalar UInt64 @specifiedBy(url: "xsd:unsignedLong")
  
  # Here xsd is the namespace <http://www.w3.org/2001/XMLSchema#>.

•  Units and quantity kind can be specified.

Unit

Dimension

• via types and enums

•  Default values can be specified.

Default

• handling of default values depends on your server-side implementation
• It can be added for informative purposes as a comment in the schema

•  Allowed values can be specified.

allowed: [‘value1’, ..., ‘valueN’]

• Use enums
  

  enum Color {
    RED
    GREEN
    BLUE
  }
  
  type Car {
    id: ID!
    make: String!
    model: String!
    color: Color!
  }

•  A custom redefinition of the concepts is possible.

Overlay

• schema stiching
• schema extension

•  Min and max expected values can be specified.

min: 0

max: 100

• custom scalar type and directive
• implementation of the necessary validation logic on the server-side
• Alternative: include the information in the comment.

•  Concepts in the model can evolve.

deprecation

• @deprecated directive