Do you use the True Name Patent Portfolio? The True Name patents are recognized as important inventions for use in distributed and cloud computing applications including search engines, file systems, content addressable storage and social media.
If you deploy any of the methods, broadly illustrated below, on your web site or server where the hash of content is or becomes its file name or identifier, depending on your particular implementation you may be practicing the True Name patents, in which case you need to obtain a license from PersonalWeb to continue your operations without further infringing PersonalWeb's patent rights.
Cache validation/invalidation/ busting - eTag
Including the hash of the content in the eTag, content file name or data identifier to determine the presence of a valid file in the cache before retrieving a hard stored version, whether or not embedded in a URL. Examples include .css and .js files used with Java and HTTP headers using resource eTags.

True Name Patent Implicated: This Cache validation/invalidation/busting - eTag method may practice at a minimum U.S. Patent #5,978,791, #6,415,280, #7,802,310, #6,928,442.
Inverted Index/Snippet
Hashing a term and storing the hash of the term as a key in a table that points to one or more documents containing that term where a query term is hashed to identify the existence of and retrieve one or more instances of the term in one or more documents that include the term, such as in snippet generation. Examples may include certain advanced Lucene/Solr or other large-scale search implementations

True Name Patent Implicated: This inverted index method may practice at a minimum U.S. Patent #5,978,791, #7,802,310.
Rsync Algorithm
Any use of the rsync algorithm to determine whether a data item exists at a certain location and then transfer of data from a source to a destination or delete data based upon that determination. Example uses include file synchronization, replication and deduplication.

True Name Patent Implicated: This rsync method may practice at a minimum U.S. Patent #5,978,791, #6,415,280, #7,802,310, #8,001,096,
Developers using these open source software programs may deploy Cache validation/invalidation/busting - eTag, Inverted Index and/or Rsync Algorithm, techniques that may practice one or more True Name patents requiring you to obtain a license.
These open source software programs utilize Cache validation/invalidation/busting - eTag, Inverted Index and/or Rsync Algorithm that may practice one or more True Name patents requiring you to obtain a license for its use.
.NET eTAG PYTHON DICTIONARIES
AJAX FILE:HASHCACHE RUBY
APACHE JIRA RUBY ON RAILS
BIT TORRENT JSON OBJECTS SHARE POINT
DJANGO MONGO WEBASSETS
DOMHASH MOZILLA