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:
“He is strong and pain is worse to the strong, incapacity is worse.”
—Robinson Jeffers (1887–1962)
“He is a strong man who can hold down his opinion. A man cannot utter two or three sentences, without disclosing to intelligent ears precisely where he stands in life and thought, namely, whether in the kingdom of the senses and the understanding, or, in that of ideas and imagination, in the realm of intuitions and duty.”
—Ralph Waldo Emerson (1803–1882)
“Sensuality often accelerates the growth of love so much that its roots remain weak and are easily pulled up.”
—Friedrich Nietzsche (1844–1900)