CSV Business Rules Engine

A design of business rules engine which handles business rules in CSV

Config Service manages (store, update, retrieve, delete etc.) configurations (configs)
Configs can be String of json, csv or any other format
Configs can be stored in DB or as files or extended to other medias e.g. git
Additional features can be added to Config Service, e.g. UI for business users to edit / approve
It can be deployed as a microservice similar to Spring Cloud Config
There are 2 options to refresh the config
a. Whenever there is an update to the config, notify the clients (Clients need to provide / implement an API)
b. Clients to check with Config Service periodically e.g. every 10s, 1min, 10min etc. And then clients can update its own cache
To improve the performance, Config Service can provide an API to retrieve only summary of the config, in case the config itself is too large

Rule Config is a kind of config, can be retrieved from ConfigService
Rule Config is NOT Rule, it's the metadata to be used when defining a Rule
Usually the business rules are stored as a table in Excel / CSV. This CSV is treated as a Rule Config When parsing the CSV, one record can be read as:

when (columnA = x and columnB = y) then use columnC
CSV format can be converted to JSON for application to process and store
JSON is for UI to render as a table for user to edit
JSON can be persisted as files or in database
If stored in database, different kinds of JSON will be store in one single table
By saving different versions of JSON into database, the application can support versioning
Rule config is OPTIONAL, it's not mandatory when creating a Rule
Other data types can be added by adding new parsers
The RuleConfigService supports cache and auto refresh cache of Rule Config

A Rule contains conditions("when") and actions("then", "otherwise"), and returns a Result
When defining a Rule, it's usual to use Rule Config, but not mandatory
There are 2 approaches to create a rule:
a. Create a java class to implement the Rule interface
b. Use the DefaultRuleBuilder to build a rule.

A "Fact" is a runtime object instance to be checked against / applied on a rule
To prevent creating different java classes for different types of fact, Jackson library's JsonNode is used as the type for fact

dwtcourses / csv-business-rules-engine