URLs and URIs

   The previous concept is that the website is URL, But I see another concept URI. Curious about the relationship between the two , So I learned , Wrote this blog . I hope this article can explain the following questions in a popular way ：
  1） What is? URI？
  2） What is? URL？
  3）URI and URL What is the relationship of ？

   Before the official start , It's useless to talk about something first . The world is so big , How can we find an exact place ？ Take Beijing for example , Through the name of Beijing, you can find the land of Beijing . let me put it another way , The name Beijing uniquely identifies this land . When you get this logo , You can find the corresponding thing . Same thing , Apply to the Internet , There are many resources on the Internet ( video 、 Images 、 Program 、 Text, etc. ), To find any of them, you should also need a specific identifier , This is related to what we are going to introduce today .

1. What is? URI？

  URI(Uniform Resource Identifier, Uniform resource identifiers ),URI Use a string to identify abstract or physical resources , It is used to uniquely identify a resource . Its focus is to determine the existence of resources , It's more of a concept . Take Beijing as an example , When I learned about the logo of Beijing , Just guide this sign to exist objectively , No matter where , Go anyway , This resource must be , And you can use Beijing logo .
   Let's see URI The composition of ：
  1） Resource naming mechanism
  2） Host name of the storage resource
  3） The name of the resource itself

ps: I'm curious about the naming mechanism of resources ？ But it's actually a general concept , Maybe different kinds of resources have different naming methods .

2. What is? URL？

  URL(Uniform Resource Locator, Uniform resource locator ),URL It can also represent a resource , And it describes all kinds of resources in a unified format .URL Will provide an address , Once you have the address, you will know the name of the resource , You can find and access this resource .

   Look again. URL The composition of ：
  1） agreement (http/https/ftp)
  2） Host with resources IP Address / domain name
  3） The specific address of the host resource

   Compare the composition of the two , Basic module correspondence . There is an obvious characteristic ,URL Will be more specific . The naming mechanism is general , But some kind of agreement is specific . The name of the resource itself is relative , The specific address of the resource is absolute .URL Specify the protocol type to use ,URI Protocol specifications are not involved

3.URI and URL The relationship between

   There is a picture that illustrates URI and URL The relationship between ：

   Picture source ：https://zhuanlan.zhihu.com/p/36627338

   in other words URL yes URI A subset of
   Analyze it in detail , Actually URI and URL Both define the concept of resources . But in terms of composition ,URL The specific implementation path is given ,URI Just stay in concept . For example, I don't know whether it's appropriate ,URI Tell you to open one party, however URL Tell you to drive party Time and place of . Both things point to this party, but URL More specifically .

   That is to say URL yes URI A way to realize the concept

   that How to distinguish URI and URL？： The only thing that can represent resources is URI, stay URI The access method given on the basis of is URL

   Now? HTTP The specification does not use URL, Use URI, Think URI More promising ( I don't know to search directly bai.com You can find the website , yes URI It works or is automatically supplemented , I'll study it later ~)

   Look at the third part of the picture ：URN(Uniform Resource Name, Unified resource name ). This means that there is URN and URL You can find the uniquely identified resource , That is to say URN Identify something ,URL Determine the way to find things .

   On the whole , Just two concepts , It's good to be able to distinguish in future applications ~

Reference material ：
https://blog.csdn.net/weixin_52148548/article/details/124431585
https://m.php.cn/article/413616.html

Due to the limited level of the author , If there are mistakes , Please indicate in the comments section below , thank you ！