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1. PDS
   1. partition data
   2. WAL records
2. Metadata
   1. binary meta
   2. marshaller
3. Communication SPI
4. Discovery SPI
5. Binary Marshaller
6. Affinity.
7. Management API
   1. argument 
   2. results
   3. tasks (class names).
8. ThinClient Protocol

Compatibility Matrix

Current Ignite codebase

• Is there any primitives, building blocks to provide compatibility?
• Difficulties for day by day coding.
• Compatibility testing.
  • explicit tests.
  • ability to run tests with random node versions
• New feature implementation, enabling.
• patterns for implementing commons cases: new version of algorithmes, testing against new versions.
• Scope of compatibility: 
  • Currently any third-party module can register own ports (messages?) and must be able to track compatibility. 

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