There are some typos in 1.2.2 Key System section, I use ////???->"proposed text" //// to show the modification.


///////////////////////////change begin/////////////////////////////////////
1.2.2. Key System

A Key System is a generic term for a decryption mechanism and/or content protection provider. Key System strings provide unique identification of a Key System. They ////"are"////  used by the user agent to select the Content Decryption Modules and identify the source of a key-related event. Simple Decryption Key Systems are supported by all user agents. User agents may also provide additional CDMs with corresponding Key System strings.

Key System ////strings -> "string"//// ////are->"is"//// always a reverse domain name. For example, "com.example.somesystem". Within a given system ("somesystem" in the example), ////subsystems->"sub Key System" /////may be defined as determined by the key system provider. For example, "com.example.somesystem.1" and "com.example.somesystem.1_5". Key system providers should keep in mind that these will be used for comparison and discovery, so they should be easy to compare and the structure should remain reasonably simple.

If a user agent returns "maybe" or "probably" for any ////subsystem->"sub key System"//// string, it must return "maybe" when a ////parent system->"parent Key System" ////string is passed to canPlayType(). For example, if a user agent returns "maybe" or "probably" for "com.example.somesystem.1_5", it must return "maybe" for "com.example.somesystem".