The present invention is directed towards systems and methods for trust propagation. The method according to one embodiment comprises calculating a first feature vector for a first user, calculating a second feature for a second user and comparing the first feature vector with the second feature vector to calculate a similarity value. A determination is made as to whether the similarity value falls within a threshold. If the similarity value falls within the threshold, a relationship is recorded between the first user and the second user in a first user profile and a second user profile.

Techniques to improve query caching performance by efficiently selecting queries stored in a cache for evaluation and increasing the cache hit rate by allowing for inexact matches. A list of candidate queries stored in the cache that potentially could be used to answer a new query is first determined. This list may include all cached queries, cached queries containing exact matches for select list items, or cached queries containing exact and/or inexact matches. Each of at least one candidate query is then evaluated to determine whether or not there is a cache hit, which indicates that the candidate query could be used to answer the new query. The evaluation is performed using a set of rules that allows for inexact matches of aggregates, if any, in the new query. A query plan is generated for the new query based on a specific candidate query with a cache hit.

Optimization constraints are used to select an appropriate content item from an available group of content items which are ordered in a specific manner to facilitate the proper selection of the content item, even if the exact item desired is not present. The server is then able to insert the selected content item into the outgoing content page requested by the client. The optimization constraints can be, but are not limited to, anyone of the following: communication channel performance (bandwidth), client operating system, client processor, client display capabilities, client installed software (video or audio codecs for example), and/or user preferences. A software product and method enable selective delivery of content to client devices of varying performance characteristics, including varying bandwidth, by selective filtering and inclusion of markup language content using tags demarcating optional content. An optimization constraint is used to select one of the items.

An electronic media distribution/play system includes a service facility that has a communications network interface and maintains a data file catalog. The catalog is sent over the network to requesting users, and the system processes payments from customers in establishing file access authorizations. Encrypted user-selected files and a player program are transmitted to each customer for metered access to received data files as limited by the authorization, and customers can make additional selections and play the encrypted files freely while the authorization remains established. The system can transmit the data files from local storage, and also provide links to encrypted files that are stored at remote vendor facilities. Authorizations can be for selected portions or class levels of the catalog, and for terms measured as calendar time, play time, and collective number of plays. Also disclosed is a method for facilitating the distribution and accessing of electronic files.

A computer-implemented system and method for generating waymarks is provided. A database of waymarks is maintained. Each waymark is associated with a category. A new waymark is generated. Geospatial data defining a location, metadata describing a physical object associated with the location, and at least one photograph of the location are received from a user. The geospatial data, metadata, and photograph are complied as the new waymark. One of the categories is assigned to the new waymark. The new waymark is added to the database. A search option is provided for accessing the waymark by at least one of the location and category.