Principle vs Rule Based

Activity-based costing (ABC) is a costing method that assigns value to each activity resource to all products and services according to the cost of its usage. it gives indirect costs (overhead) into direct costs so that an organization can correctly estimate the cost of its individual products and services to identify and eliminate the unprofitable and lower the prices of the overpriced. Normally, it is used as a tool for understanding product and customer cost and profitability. But ABC has also been used to support strategic decisions like pricing, outsourcing, identification and measurement of process improvement initiatives. ABC can be used for external reports, but mostly it is used for internal purposes. External reports don’t not need to be as detailed. Some cost are reported, however breakdowns may not be included.
Grenzplankostenrechnung (GPK), roughly translating to "flexible standard costing," is the costing systems used heavily in Germany and other European countries. Companies that use GPK work towards identifying cost behaviors, traceability, relevance to decision making, and cost period measurement. The main idea behind GPK is the responsibility center. GPK helps keep cost centers in control in areas such as cost planning and cost control and measures efficiency. But GPK does not give management information needed concerning indirect cost centers and it is always changing and being revised demanding more personnel.
Lean accounting is designed for companies who have implemented lean manufacturing techniques. Traditional cost accounting cannot always accurately reflect the positive and cost saving measures that a lean system provides. Since many of a company's choices are made from crunching numbers that the accounting department provides, benefits are overlooked using traditional accounting methods. The principles of lean accounting are to measure and motivate.
Resource consumption accounting (RCA) is a comprehensive cost management system