Abstract: Scalable leases reduce latency and reduce the burden on a server in managing data leases. Instead of processing individual lease requests for clients seeking access to the same data, scalable leases provide for blanket leases that all of the clients can use to access the selected data. Leases may be encrypted or selectively distributed to restrict access to the data. Moreover, distributed data structures may be used to cache leases at identifiable nodes in a network to offload work from the server without all clients in the network having to cache all blanket leases issued. Thresholds for issuing blanket leases may be determined or adjusted by considerations such as demand for the selected data and server workload. Similarly, leases may be renewed on the basis of demand for selected data, conflicting lease requests, and other factors. Scalable leases may be issued for read leases and controlled write leases.

Abstract: The claimed subject matter provides a system and/or a method that facilitates optimally and efficiently utilizing an image file format. A server can host an image that is partitioned into two or more tiles, wherein the two or more tiles collectively represent the image in entirety and are defined in at least one image file format. A tile generator can evaluate at least one tile to identify a suitable image file format based upon at least one of a characteristic of such file format or a context of a use for the tile. A browser can utilize the tile in the identified file format in order to render a portion of the image.

Abstract: Intent of a user is determined with respect to mapping information. A search is performed for relevant maps from a plurality of disparate sources. A subset of maps from a superset of available maps are identified that correlate to the determined intent, and the subset of maps are fused or synthesized to create a single map view that aggregates and combines relevant content from respective maps of the subset.

Abstract: Non-mutating tree-structured file identifiers are used to identify files stored in a file system. Each of multiple files in the file system has a corresponding non-mutating file identifier, and these file identifiers are assigned and maintained using a tree structure.

Abstract: Architecture for encoding (or packaging) vector-object data using fixed boundary tiles. Tiling a large vector database provides the same advantages that tiling provides for a large raster image. Tiling the dataset means that the set of all possible browser requests is finite and predetermined. The tiles can be rasterized on a client once the tiles have been received from a server. Alternatively, the server can do the tiling and rasterizing, and then send the raster data to the client for presentation and user interaction. Tiles can be precomputed on the server, with selected tiles then transmitted to the client for rasterization. Moreover, tiles can be cached for improved performance, and prefetched based on user interactivity on the client. Summarization of the vector-object data can be accomplished at the server using a configurable plug-in interface.

Abstract: The clocks of remote computing devices are synchronized within a range of certainty through the determination of an upper bound and a lower bound around a reference time. A message from a computing device is propagated up a network tree of devices to a device having a reference time, which encodes the reference time and returns the message down the tree. Each receiving device can determine that the reference time could not have occurred before their transmission of the message, nor could it have occurred after their receipt of the return message. Cryptographic hashes can be used to guard against malicious computing devices. Alternate paths and scheduling of messages can be used to provide a narrower spread between the upper and lower bounds, and clock drift can be accounted for by increasing the spread over time.

Abstract: Digital maps can be composed of a series of image tiles that are selected based on the context of the map to be presented. Independently hosted tiles can comprise additional details that can be added to the map. A manifest can be created that describes the layers of map details composed of such independently hosted tiles. Externally referable mechanisms can, based on the manifest and map context, select tiles, from among the independently hosted tiles, that correspond to map tiles being displayed to a user. Subsequently, the mechanisms can instruct a browser, as specified in the manifest, to combine the map tiles and the independently hosted tiles to generate a more detailed map. Alternatively, customized mechanisms can generate map detail tiles in real-time, based on an exported map context. Also, controls instantiated by the browser can render three-dimensional images based on the combined map tiles.

Abstract: A delta pager maintains a database with atomic, isolated transactions. When a transaction seeks to make changes to the database, the delta pager stores the changes in write buffers, and applies the changes when intervening transactions do not literally or substantively change the state of the database relied upon by the transaction. The delta pager applies the changes to commit the transaction by conjoining the write buffers with the current state of the database to form a new data structure representing the state of the database. The delta pager coalesces write buffers to maintain efficiency, subject to snapshots the delta pager respects to preserve selected states of the database. The delta pager makes selected sections of the database durable by moving selected data to a durable store. The delta pager also provides cache objects between the durable store and current transactions to promote efficient access to data.

Abstract: A system is disclosed that transforms offline maps into interactive online maps. In the system, geo-coordinate relationships are determined between geo-coordinates on a source map and geo-coordinates on an online reference map. An image of the source map is transformed to form an image of a modified source map having geo-coordinates that substantially align with corresponding geo-coordinates on the reference map. Modified source tiles are formed with the image of the modified source map and displayed on a portion of the reference map.

Abstract: A distributed computing system can be operated in a fault tolerant manner using a set of computing devices. A set of computing devices can tolerate a number of failures by implementing identical replicas of a state machine and selecting proposals. The set of computing devices participating in the distributed computing system by hosting replicas can be modified by adding or removing a computing device from the set, or by specifying particular computing devices for participation. Changing the participating computing devices in the set increases fault tolerance by replacing defective devices with operational devices, or by increasing the amount of redundancy in the system.

Abstract: Each file in a file system has one or more associated metadata fields, and each metadata field is associated with a different lease. A computing device sends a request to a directory server for one or more leases that are needed by the computing device to perform an operation on a file. The directory server receives the request from the computing device and determines whether the operation can succeed. One or more leases to perform the operation are issued to the computing device if it is determined that the operation can succeed, and one or more leases that reveal failure are issued to the computing device if it is determined that the operation cannot succeed. The computing device receives the issued lease(s) and uses the received lease(s) to determine whether the computing device can perform the operation on the file.