All PTA tools have in common that they model accounting as a programming language, as opposed to data. This provides for a high degree of epressiveness and flex

All PTA tools have in common that they model accounting as a programming language, as opposed to data. This provides for a high degree of epressiveness and flexibility which is hard to achieve with database accounting tools that are typically data-oriented. The basic instructions are open account, close account, and update account (transaction). In addition, a lot of PTA tools support some form of higher-order directives: directives that generate other directives. For example, the availability of prices might trigger the insertion of valuation transactions based on the change of value for a balance position, when processing the balance. Or declarative accrual transactions for a given date might insert "virtual" transactions at specific other dates. The PTA / language-centric view allows to reason about those very easily, as abstractions which result in AST rewrites.