12 Appendix D Network Model customer 、depositor customer account savings_account checking_account savings_account checking_account (a) (b) Figure D.17 Data-structure and E-R diagram. has several addresses.In this case,the customer record type will have the (street, city)pair of fields defined as a repeating group.Thus,the customer record for Turner may be as in Figure D.18. The repeating-groups construct provides another way to represent the notion of weak entities in the E-R model.As an illustration,let us partition the entity set customer into two sets: 1.customer,with descriptive attribute customer name 2.customer address,with descriptive attributes customer_street and customer_city The customer nddress entity set is a weak entity set,since it depends on the strong entity set customer. The E-R diagram describing this schema appears in Figure D.19a.If we do not use the repeating-group construct in the schema,then the corresponding data- Turner Putnam Stamford Field Horseneck Figure D.18 A customer record.12 Appendix D Network Model Figure D.17 Data-structure and E-R diagram. has several addresses. In this case, the customer record type will have the (street, city) pair of fields defined as a repeating group. Thus, the customer record for Turner may be as in Figure D.18. The repeating-groups construct provides another way to represent the notion of weak entities in the E-R model. As an illustration, let us partition the entity set customer into two sets: 1. customer, with descriptive attribute customer name 2. customer address, with descriptive attributes customer street and customer city The customer address entity set is a weak entity set, since it depends on the strong entity set customer. The E-R diagram describing this schema appears in Figure D.19a. If we do not use the repeating-group construct in the schema, then the corresponding data￾Figure D.18 A customer record