Protocol Buffers 3.0 发布，该版本与上一个稳定版 2.6.1 版本比较，主要改进包括：
全面的 3.0 协议版本 proto3：
废弃 optional 关键字
Removed non-zero default values and field presence logic for non-message fields.
Group fields are no longer supported in proto3 syntax.
Changed repeated primitive fields to use packed serialization by default in proto3 (implemented for C++, Java, Python in this release).
Added well-known type protos (any.proto, empty.proto, timestamp.proto, duration.proto, etc.).
Proto3 JSON is supported in several languages (fully supported in C++, Java, Python and C# partially supported in Ruby).
Proto3 enforces strict UTF-8 checking.
其他各方面的改进详情请看：
https://github.com/google/protobuf/releases/tag/v3.0.0
Protocol Buffers (ProtocolBuffer/ protobuf )是Google公司开发的一种数据描述语言，类似于XML能够将结构化数据序列化，可用于数据存储、通信协议等方面。