Object-Oriented Databases Need for Complex Data Types - CWI
Object-Oriented Databases Need for Complex Data Types - CWI
Object-Oriented Databases Need for Complex Data Types - CWI
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<strong>Data</strong>base System Concepts<br />
ODMG C++ ODL: Example (Cont.)<br />
class Customer : public Person {<br />
public:<br />
d_Date member_from;<br />
d_Long customer_id;<br />
d_Ref home_branch;<br />
d_Set accounts; };<br />
<strong>Data</strong>base System Concepts<br />
8.29<br />
Implementing Relationships<br />
8.30<br />
©Silberschatz, Korth and Sudarshan<br />
Relationships between classes implemented by references<br />
Special reference types en<strong>for</strong>ces integrity by adding/removing<br />
inverse links.<br />
Type d_Rel_Ref is a reference to Class, where<br />
attribute InvRef of Class is the inverse reference.<br />
Similarly, d_Rel_Set is used <strong>for</strong> a set of references<br />
Assignment method (=) of class d_Rel_Ref is overloaded<br />
Uses type definition to automatically find and update the inverse<br />
link<br />
Frees programmer from task of updating inverse links<br />
Eliminates possibility of inconsistent links<br />
Similarly, insert_element() and delete_element() methods of<br />
d_Rel_Set use type definition to find and update the inverse link<br />
automatically<br />
©Silberschatz, Korth and Sudarshan<br />
15
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