最病 A Detection o Detect a mismatch between two versions of an object s generating class a Two categories of detection policy: 口 Nominal approach: each class version has a version name a Central registration mechanism necessary 口 Structural approach Deduce class descriptor from actual class structure Store class descriptor Simple detection: compare class descriptors of retrieved object with new class descriptor Institute of Computer Software 2021/1/28 Nanjing UniversityDetection  Detect a mismatch between two versions of an object’ s generating class  Two categories of detection policy:  Nominal approach: ◼ Each class version has a version name ◼ Central registration mechanism necessary  Structural approach: ◼ Deduce class descriptor from actual class structure ◼ Store class descriptor ◼ Simple detection: compare class descriptors of retrieved object with new class descriptor 2021/1/28 Institute of Computer Software Nanjing University 50