DTRules
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Creating Projects

This guide walks through creating a new DTRules project. We'll build a simple discount calculation system to demonstrate the process.

Go This guide uses Go CLI tools. See Choosing an Implementation for an overview of available tools.

Project Setup

1. Copy the Template

Start with the TestProject template:

cp -r sampleprojects/TestProject sampleprojects/MyProject
cd sampleprojects/MyProject

2. Update Configuration

Edit DTRules.xml with your project details:

<DTRules>
  <compiler>EL</compiler>

  <RuleSet name="MyProject" source="file">
    <RuleSetFilePath>/xml</RuleSetFilePath>
    <WorkingDirectory>/temp</WorkingDirectory>

    <DTExcelFolder>/DecisionTables/</DTExcelFolder>
    <EDDExcelFolder>/edd/</EDDExcelFolder>

    <Entities        name="MyProject_edd.xml" />
    <Decisiontables  name="MyProject_dt.xml"  />
    <Map             name="MyProject_map.xml" />
  </RuleSet>
</DTRules>

3. Update pom.xml

<groupId>com.mycompany</groupId>
<artifactId>myproject</artifactId>
<version>1.0-SNAPSHOT</version>
<name>MyProject</name>

Define Your Data Model

Create the EDD

Create edd/MyProject_edd.xls with your entities:

Entity Attribute Type Subtype Default Comment
Order Customer order
customer Customer Who placed the order
items array LineItem Order line items
subtotal decimal 0 Pre-discount total
discount decimal 0 Applied discount
total decimal 0 Final total
Customer Customer info
name string
vip boolean false VIP status
member_since date Membership date
LineItem Order line
product string
quantity integer 1
unit_price decimal 0
line_total decimal 0
Context Global config
today date Current date
vip_discount decimal 0.15 VIP discount rate
bulk_threshold decimal 100 Bulk order threshold
bulk_discount decimal 0.10 Bulk discount rate

Write Decision Tables

Create the Decision Tables

Create DecisionTables/MyProject_dt.xls:

Table: Main

Name: Main
Type: ALL
Description: Main entry point for order processing

Actions:
  - perform Calculate_Line_Totals
  - perform Calculate_Subtotal
  - perform Apply_Discounts
  - perform Calculate_Total

Table: Calculate_Line_Totals

Name: Calculate_Line_Totals
Type: ALL
Description: Calculate each line item total

Actions:
  for each item in order.items do
    set item.line_total = item.quantity * item.unit_price
  done

Table: Calculate_Subtotal

Name: Calculate_Subtotal
Type: ALL
Description: Sum line totals to get subtotal

Actions:
  set order.subtotal = 0
  for each item in order.items do
    set order.subtotal = order.subtotal + item.line_total
  done

Table: Apply_Discounts

Name: Apply_Discounts
Type: FIRST
Description: Apply the best applicable discount

Conditions:
  1. customer.vip = true
  2. order.subtotal >= bulk_threshold

| Condition    | R1 | R2 | R3 | R4 |
|--------------|----|----|----|----|
| VIP          | Y  | Y  | N  | N  |
| Bulk Order   | Y  | N  | Y  | N  |
|--------------|----|----|----|----|
| VIP Discount | X  | X  | -  | -  |
| Bulk Discount| -  | -  | X  | -  |
| No Discount  | -  | -  | -  | X  |

Actions:
  - set order.discount = order.subtotal * vip_discount
  - set order.discount = order.subtotal * bulk_discount
  - set order.discount = 0

Table: Calculate_Total

Name: Calculate_Total
Type: ALL
Description: Apply discount to get final total

Actions:
  set order.total = order.subtotal - order.discount

Build the Rules

Run dtrules build from the project directory. It extracts the DSL from Excel to XML and compiles it to postfix — Excel is the system of record, and the same DSL is written back to Excel in the same step: 

cd /path/to/DTRules/sampleprojects/MyProject
dtrules build

This generates the XML files in the xml/ directory. (The old dtrules -compile command and build --from-xml flag have been removed — use dtrules build.)

Test the Rules

Create Test Cases

Create test XML files in testfiles/:

<!-- testfiles/test1.xml -->
<data>
  <order>
    <customer>
      <name>John Doe</name>
      <vip>true</vip>
    </customer>
    <items>
      <item>
        <product>Widget</product>
        <quantity>5</quantity>
        <unit_price>10.00</unit_price>
      </item>
    </items>
  </order>
</data>

Run with Go CLI Go

Once you have compiled XML files, you can execute them with the Go CLI:

cd /path/to/DTRules/go
go build -o dtrules ./cmd/dtrules

./dtrules -rules ../sampleprojects/MyProject/xml -entry Main -trace

Run with REST API

Start the REST API server and send test requests for production-style integration.

Using the Visual UI

Once your project is compiled to XML, you can use the visual UI:

  1. Start the backend: cd go && go run ./cmd/api
  2. Start the UI: cd ui && npm run dev
  3. Click "Open Custom Project"
  4. Enter the path to your xml/ directory
  5. Explore and edit your rules visually

Best Practices

  • Start small - Begin with a minimal model and expand
  • Test early - Write tests as you develop rules
  • Use meaningful names - Entities and tables should be self-documenting
  • Keep tables focused - One decision per table
  • Document business logic - Use descriptions to explain the "why"

Next Steps