SDTL Pseudocode Library Schema

A Pseudocode Library is a set of templates used to translate SDTL into natural language, which is represented in a JSON file. Table 1 describes the JSON properties in the Pseudocode Library. Every $type in the SDTL schema is described by a template identified with a corresponding “SDTLname” in the Pseudocode Library.

The Pseudocode Library provides templates with locations to be filled with the values of properties in the SDTL command. For example, the template for the SDTL Compute command is:

Set {variable} to {expression}.

The bracketed words refer to properties of the Compute command: “variable” and “expression”. In the example described below “variable” is equal to “pvar1” and “expression” is equal to “10”. When we put these values into the template, we get:

Set pvar1 to 10.

Figure 1 shows the Pseudocode Library JSON for the SDTL Compute command as well as the NumericConstantExpression and VariableSymbolExpression SDTL types. As often happens in SDTL, the properties of the Compute command are expressed as other SDTL elements. Figure 2 shows how NumericConstantExpression and VariableSymbolExpression are nested in the SDTL Compute command.

The schema for the Pseudocode Library is described in Table 1. Every element in SDTL is identified by an “SDTLname”. The basic template for an element is given in the “baseText” property, which may only consist of a reference to a property within the element.

Table 1. Properties of the Pseudocode Library JSON File

SDTLname	Name of the $type in SDTL
baseText	Basic template for this SDTL element
notes	Guidance about this template
parameters	Properties of this SDTL $type
	propertyName	Name of the property
	repeated	If “yes”, this property may be repeated
	reqType	May be the $type of an SDTL element used for this property or “boolean”
	text	Template for use with this property

Properties of an SDTL element are described in the “parameters” array of the Pseudocode Library. All properties have names, which are found in the schema for SDTL. The “text” property of a “parameter” provides a template that is only used if the property is present or takes the value TRUE for boolean types. If “text” is present, it follows the “baseText”.

The “reqType” property of a “parameter” fulfills two functions. First, SDTL includes elements that are not explicitly identified with a “$type” parameter. For example, a script can use one SDTL Rename command to change the names of more than one variable. Variables to be renamed are described in the “renames” array. Each element in the “renames” array is an SDTL RenamePair type consisting of an “oldVariable” and a “newVariable”. Since the elements in the “renames” array must be of “$type” RenamePair, the “$type” property can be omitted. We use the “reqType” property in the Pseudocode Library to specify when a particular SDTL “$type” is required. This simplifies the task of the Pseudocode Translator by eliminating the need to lookup the “$type” of elements in the “renames” array in the SDTL schema.

Second, some properties in SDTL take boolean (true/false) values. When a “reqType” is declared as “boolean”, the “text” associated with that “parameter” is only used when its value is “true”.

Figure 1. Extract from the Pseudocode Library

{
  "PseudocodeLibrary": [
    {
      "SDTLname": "Compute",
      "BaseText": "Set {variable} to {expression}",
      "notes": null,
      "parameters": [
        {
          "PropertyName": "variable",
          "Repeated": "No",
          "reqType": null,
          "text": null
        },
        {
          "PropertyName": "expression",
          "Repeated": "No",
          "reqType": null,
          "text": null
        },
        {
          "PropertyName": "messageText",
          "Repeated": "Yes",
          "reqType": null,
          "text": "\\n **** {message} *****"
        }
      ]
    },
    {
      "SDTLname": "NumericConstantExpression",
      "BaseText": "{value}",
      "notes": null,
      "parameters": [
        {
          "PropertyName": "value",
          "Repeated": "No",
          "reqType": null,
          "text": null
        },
        {
          "PropertyName": "numericType",
          "Repeated": " of type {numericType}",
          "reqType": null,
          "text": null
        }
      ]
    },
    {
      "SDTLname": "VariableSymbolExpression",
      "BaseText": "{variableName}",
      "notes": null,
      "parameters": [
        {
          "PropertyName": "variableName",
          "Repeated": "No",
          "reqType": null,
          "text": null
        }
      ]
    }
  ]
}

Figure 2. Extract from SDTL JSON file: Compute command.

{
   "$type": "Compute",
   "command": "compute",
   "sourceInformation": {
       "originalSourceText": "compute pvar1 = 10."
   },
   "variable": {
       "$type": "VariableSymbolExpression",
       "variableName": "pvar1"
   },
   "expression": {
       "$type": "NumericConstantExpression",
       "value": "10",
       "numericType": "int"
   }
}