为什么UUID以“ 8-4-4-4-12”（数字）格式显示？由于这个原因，我环顾四周，但找不到所需的决定。
格式化为十六进制字符串的UUID的示例：58D5E212-165B-4CA0-909B-C86B9CEE0111
Answers:
time, version, clock_seq_hi, clock_seq_lo, node如下面的rfc所示，它由分隔。
4.1.2. Layout and Byte Order
To minimize confusion about bit assignments within octets, the UUID
record definition is defined only in terms of fields that are
integral numbers of octets. The fields are presented with the most
significant one first.
Field Data Type Octet Note
#
time_low unsigned 32 0-3 The low field of the
bit integer timestamp
time_mid unsigned 16 4-5 The middle field of the
bit integer timestamp
time_hi_and_version unsigned 16 6-7 The high field of the
bit integer timestamp multiplexed
with the version number
clock_seq_hi_and_rese unsigned 8 8 The high field of the
rved bit integer clock sequence
multiplexed with the
variant
clock_seq_low unsigned 8 9 The low field of the
bit integer clock sequence
node unsigned 48 10-15 The spatially unique
bit integer node identifier
In the absence of explicit application or presentation protocol
specification to the contrary, a UUID is encoded as a 128-bit object,
as follows:
The fields are encoded as 16 octets, with the sizes and order of the
fields defined above, and with each field encoded with the Most
Significant Byte first (known as network byte order). Note that the
field names, particularly for multiplexed fields, follow historical
practice.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time_low |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time_mid | time_hi_and_version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|clk_seq_hi_res | clk_seq_low | node (0-1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| node (2-5) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
该格式在IETF RFC4122的第3节中定义。输出格式定义为“ UUID = ...”。
3.-命名空间注册模板
命名空间ID：UUID注册信息：注册日期：2003-10-01
声明的名称空间注册人：JTC 1 / SC6（ASN.1报告人组）
句法结构的声明：UUID是相对于所有UUID的空间在时间和空间上都是唯一的标识符。由于UUID是固定大小且包含时间字段，因此值可能会翻转（大约在AD 3400左右，具体取决于所使用的特定算法）。UUID可以用于多种用途，从标记寿命极短的对象到可靠地识别网络中非常持久的对象。
The internal representation of a UUID is a specific sequence of bits in memory, as described in Section 4. To accurately represent a UUID as a URN, it is necessary to convert the bit sequence to a string representation. Each field is treated as an integer and has its value printed as a zero-filled hexadecimal digit string with the most significant digit first. The hexadecimal values "a" through "f" are output as lower case characters and are case insensitive on input. The formal definition of the UUID string representation is provided by the following ABNF [7]: UUID = time-low "-" time-mid "-" time-high-and-version "-" clock-seq-and-reserved clock-seq-low "-" node time-low = 4hexOctet time-mid = 2hexOctet time-high-and-version = 2hexOctet clock-seq-and-reserved = hexOctet clock-seq-low = hexOctet node = 6hexOctet hexOctet = hexDigit hexDigit hexDigit = "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" / "a" / "b" / "c" / "d" / "e" / "f" / "A" / "B" / "C" / "D" / "E" / "F"