Institute of Information Science - University of Miskolc

Syntax Graphs

Syntactic rules can also be modeled using graphs, for example in the following way:

The idea is to represent all possibilities of the BNF formula in some graphical way.

1. Example: Syntax Graph for Variable Declarations in the PASCAL Language

Even if someone is unfamiliar with the PASCAL language, they would be able to declare syntactically correct variables using the graph:

var age, weekdays : integer;
var taxrate, netIncome : real;
var choice, isready : boolean;
  initials, grade : char;
  name, surname : string;

This shows how graphical representations can help understand and construct syntactically correct structures in programming languages.

2. Example: Syntax Graph of the JSON (JavaScript Object Notation) Data Exchange Format with Examples

The JSON format is very important in modern information technology. By looking at examples and the syntax graph, we can understand its structure.

Simple JSON Data

{
   {"title": "Poetry Collection", "author": "Name of the Poet"}
}

This is an object that contains name-value pairs or arrays, combined in various ways. For example:

{
  "menu": {
    "id": "file",
    "value": "File",
    "popup": {
      "menuitem": [
        {"value": "New", "onclick": "CreateNewDoc()"},
        {"value": "Open", "onclick": "OpenDoc()"},
        {"value": "Close", "onclick": "CloseDoc()"}
      ]
    }
  }
}

This example shows how JSON can be used to structure objects, where properties have values and methods. The syntax graph helps visualize the relationships between objects, arrays, and values.

JSON object:

JSON array:

JSON types:

JSON string:

JSON number:

For example: -0.123E+10 or 12.324