Drools - DSL

title

Drools - DSL

author

Bernard Szlachta (NobleProg Ltd)

What is Domain Specific Language ⌘

• " a way of creating a rule language that is dedicated to your problem domain"
• DSL is ultimately transformed to rules (mvel or java)
• .dsl file contain the transformations (mapping)
• DSLs have no impact on the rule engine at runtime, they are just a compile time feature

什么是领域特定语言 。

• " 创建规则的语言，为你的问题领域而特别设计"
• DSL最终将转换为规则 (mvel or java)
• .dsl文件包含了转换器 (mapping)
• DSLs 在运行时刻（runtime）对规则引擎无影响，他们只用于编译

When to use DSL ⌘

• Your requirements should be executable and always in sync with what is actually executed
• Analysts can focus on "logic proper"
• You already have a rules written in SBVR or other standard (which is consistent and detailed enough to be easily translated into executable rules)
• You need "templates" for conditional elements and consequence actions that are used repeatedly in your rules (with minor variations)

什么时候使用 DSL 。

• 你的需求应该能被执行并且和实际执行的要永远同步
• 分析师可以专注于“逻辑准确”（ "logic proper"）
• 你已经有SBVR或者其它标准 （一致且足够详细，可以很容易翻译为可执行规则）写的规则
• 你的规则里多处需要条件判断和结果动作（consequence actions），你需要一套模板(需要稍有改动)

DSL in Guvnor ⌘

Create New -> New DSL

[when]Order is greater than {totalOrder} = sc :ShoppingCart( $totalPrice : totalPrice > {totalOrder})
[then]Set discount to {discount} = sc.setTotalPrice( $totalPrice * (1-{discount}) ); update(sc); 

1. Create New -> New Rule
2. Type (format) of rule: DSL or Guided Ruls

dilect "mvel"
when
 Order is greater than 10000
then
 Set discount to 0.1

Use the test created for tall order discount

Guvnor里的DSL 。

Create New -> New DSL

[when]Order is greater than {totalOrder} = sc :ShoppingCart( $totalPrice : totalPrice > {totalOrder})
[then]Set discount to {discount} = sc.setTotalPrice( $totalPrice * (1-{discount}) ); update(sc); 

1. Create New -> New Rule
2. Type (format) of rule: DSL or Guided Ruls

dilect "mvel"
when
 Order is greater than 10000
then
 Set discount to 0.1

Use the test created for tall order discount

Eclipse ⌘

See 08.1DSL folder

Eclipse 。

见 08.1DSL 文件夹

Connecting DSL file with DSRL file⌘

连接 DSL 文件和 DSRL 文件。