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:
“All of us recognize the great benefits to our own nation and to the world of a strong and progressive Iran. Your support of the Camp David accords and your encouragement of the leaders who are or may be involved in consummating the peace effort would be very valuable.”
—Jimmy Carter (James Earl Carter, Jr.)
“You mustn’t give your heart to a wild thing. The more you do, the stronger they get. Until they’re strong enough to run into the woods or fly into a tree. And then to a higher tree. And then to the sky.”
—George Axelrod (b. 1922)
“A weak man is just by accident. A strong but non-violent man is unjust by accident.”
—Mohandas K. Gandhi (1869–1948)