Strong and Weak Validation
The ETag mechanism supports both strong validation and weak validation. They are distinguished by the presence of an initial "W/" in the ETag identifier, as:
"123456789" -- A strong ETag validator W/"123456789" -- A weak ETag validatorA strongly validating ETag match indicates that the content of the two resources is byte-for-byte identical and that all other entity fields (such as Content-Language) are also unchanged. Strong ETags permit the caching and reassembly of partial responses, as with byte-range requests.
A weakly validating ETag match only indicates that the two resources are semantically equivalent, meaning that for practical purposes they are interchangeable and that cached copies can be used. However the resources are not necessarily byte-for-byte identical, and thus weak ETags are not suitable for byte-range requests. Weak ETags may be useful for cases in which strong ETags are impractical for a web server to generate, such as with dynamically-generated content.
Read more about this topic: HTTP ETag
Famous quotes containing the words strong and, strong and/or weak:
“The weak are the most treacherous of us all. They come to the strong and drain them. They are bottomless. They are insatiable. They are always parched and always bitter. They are everyone’s concern and like vampires they suck our life’s blood.”
—Bette Davis (1908–1989)
“There is only one vice, which may be found in life with as strong features, and as high a colouring as needs be employed by any satyrist or comic poet; and that is AVARICE.”
—David Hume (1711–1776)
“When hearts have one mingled,
Love first leaves the well-built nest;
The weak one is singled
To endure what it once possessed.
O Love! who bewailest
The frailty of all things here,
Why choose you the frailest,
For your cradle, your home, and your bier.”
—Percy Bysshe Shelley (1792–1822)