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DSL-DESIGN.md

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DSL Design

Preamble

  • What concepts can we borrow that are already known to non-geeks
  • Rules should be readable as english sentences and we accept a more cluttered parser (IS vs. WAS vs. WERE)

Concepts

Grouping

  • ANY/ALL is used with search UIs and the like

Boolean logic

  • <PROPOSITION> IS TRUE|FALSE
  • <PROPOSITION> <PREDICATE> <VALUE>

Predicates

  • IS GREATER THAN
  • IS GREATER THAN OR EQUAL TO
  • IS NOT GREATER THAN
  • IS NOT GREATER THAN OR EQUAL TO
  • IS LESS THAN
  • IS LESS THAN OR EQUAL TO
  • IS NOT LESS THAN
  • IS NOT LESS THAN OR EQUAL TO
  • IS
  • IS NOT

Access to properties of objects

  • PROPERTY OF SOMETHING

Date operands

  • TWO MONTHS AGO

First class types for percentages, dates currencies

  • 10%
  • 1200¤

Examples

  • LAST LOGIN OF USER WAS LESS THAN TWO MONTHS AGO
  • MEMBERSHIP OF USER IS NOT PREMIUM

Todos

  • Date handling
  • Percentage handling
  • Currency handling

Examples

Shopping vouchers

RETURN 10% IF ALL RULES APPLY
BEGIN
    REVENUE OF CUSTOMER IS GREATER THAN OR EQUAL 100
    GENDER OF CUSTOMER IS FEMALE
END

RETURN 20% IF ALL RULES APPLY
BEGIN
    PURCHASES OF CUSTOMER ARE GREATER THAN OR EQUAL 2
    GROUPS OF CUSTOMER IS FRIENDS
END

RETURN 100¤ IF ANY RULE APPLIES
BEGIN
    PURCHASES OF CUSTOMER ARE GREATER THAN OR EQUAL 10
    REVENUE OF CUSTOMER IS GREATER THAN OR EQUAL 1000
END

Implement tax rules

RETURN 19 IF ALL RULES APPLY
BEGIN
    COUNTRY OF SHIPPING ADDRESS IS GERMANY
    ZIP OF SHIPPING ADDRESS IS NOT 78266
    ZIP OF SHIPPING ADDRESS IS NOT 43423
END

Control content of a start page

RETURN FRIEND_TEASER IF ALL RULES APPLY
BEGIN
    FRIENDS OF USER ARE LESS THAN 10
    AGE OF USER IS LESS THAN 30
END