How were expense items, procurement specifications represented in your budget management system? What data model was used?

In the budget management system, expense items and procurement specifications are usually represented as a hierarchical data model.

Main elements of the model:

• Expense Item — an entity describing a category of expenses (e.g., "Office Expenses", "Procurement of Materials"). Often implemented as a directory with nesting capabilities (parent and child items).
• Procurement Specification — detailed information about specific procurements, including details about goods/services, quantity, price, and suppliers.

The data model is built on related tables:

ExpenseItems (ID, Name, ParentID)
ProcurementSpecifications (ID, ExpenseItemID, Name, Quantity, Price, SupplierID)

This approach allows flexible reporting on expenses, analyzing the budget by items and procurement details, and maintaining a hierarchy for ease of classification of costs.