discussed in the context of an accounting reality given below : Fig. . : Symbols used for constructing an ER diagram Meaning Symbols Entity Type as Rectangular Box Weak entity Type as double lined Rectangular Box Relationship Type as diamond shaped Box Identifying relationship Type as double lined diamond shaped Box Attribute names enclosed in ovals and attached to their entity type by straight lines. Key attribute names enclosed in ovals and attached to their entity type by straight lines.
Multi-valued attributes by double ovals. Derived attributes by dashed line Ovals Total participation of E2 in R Cardinality Ratio : N for E1 : E2 in R R E1 E2 R E2 E1 Accounting Reality Describing the System of Accounting Using a hypothetical example of accounting system of an organisation, following statements of reality becomes the starting point of discussion in describing the ER Model concepts. Example Reality : Accounting Transactions of an organisation are documented using a voucher. Each vouchers is assigned a serial number, which begins with “ ” indicating first vouchers of the accounting period.
There is only one simple transaction voucher used for documenting the transactions (See Figure : . ). Each voucher documents date of transaction, account name along with its account code for debit as well as credit entry. Each voucher indicates the amount and narration with respect to accounting transaction.
Support documents such as bills, receipts, contracts, etc. also may be attached to an accounting voucher. Each Voucher is prepared by a particular Employee and authorised by another employee. There is an exhaustive list of Accounts with respect to which the transactions are documented.
Each Account carries a unique numeric code with its width equal to six digits. Each Account is classified as belonging to one of the Accounts Types : Expenditure, Income, Assets and Liabilities. Fig. .
: Example reality on accounting system