摘要:
A database system is provided for interchanging visually faithful renderings of fully formatted electronic documents among computers having different hardware configurations and different software operating environments for representing such documents by different encoding formats and for transferring such documents utilizing different file transfer protocols. All format conversions and other activities that are involved in transferring such documents among such computers essentially are transparent to their users and require no a priori knowledge on the part of any of the users with respect to the computing and/or network environments of any of the other users. All database operations are initiated and have their progress checked by means of a remote procedure call protocol which enables client applications to obtain partial results from them relatively quickly, without having to wait for such operations to complete their work. These database operations are forked as child processes by a main database server program, so the functionally of the database system may be extended easily by adding further database operation programs to it.
摘要:
As an electronic pen (16) moves across a display screen (12), a position resolver (14) generates a series of x,y-coordinate positions which are sent to a remote computer system (20) having a relatively high latency or time delay before the positions are processed and intended display information is returned to the memory cells of a memory array (24) which controls the display on the display screen (12). During the time delay, a temporary display of the trajectory is created, preferably in light gray or another distinguishable color. Each x,y-coordinate position is compared (32) with an immediately preceding coordinate position to determine whether the pen has moved. If so, the new coordinate is stored in a memory (36) which stores a preselected number of the most recent coordinate positions and to a toggle circuit (38) which toggles a preselected bit of the display information stored in the corresponding memory cell of the memory array. After a preselected time, determined by clocking the recent coordinate position memory (36), the oldest stored coordinate position is clocked out and display information in the memory cell corresponding to the clocked out coordinate position is retrieved (42) and analyzed (44). If the toggled bit is still in the toggled position, the toggle circuit (38) toggles it back to the initial state. If the preselected bit has been reset by the intended drawing in the interim, it is not altered.
摘要:
A computer program is disclosed for reclaiming unreferenced computer memory space, also known as garbage collection. The program operates in a virtual memory environment wherein user memory space is divided into pages. For each active page, a table stores the age of the oldest object on the page (A-value) and the age of the youngest object pointed to from that page (F-value). A generational partition divides the pages into "safe" pages and "threatened" pages, based on their A-values. Rescuer pages, which may contain pointers to threatened pages, are determined by comparing the F-values to the generational partition. All potential pointers on the rescuing pages are traced and the objects pointed to are marked as reachable. All objects reachable from other reachable objects are also marked. Unmarked threatened objects are de-allocated.
摘要:
A method of redeeming for a seller electronic payments generated by and received from a customer using a master key unknown to the seller. In anticipation of making electronic payments, a customer sends a bank the master key that he will use to generate electronic payments. The bank stores the master key. Later, the bank receives from the seller a redemption request including a seller identifier, a first value of a payment index, and an electronic payment associated with the first value of the payment index. The bank authenticates the electronic payment by comparing the electronic payment to a hash of a string including the master key, the seller identifier, and the first value of the payment index. If the electronic payment is authenticated, the bank determines an amount due to the seller and credits that amount to the seller.
摘要:
A method of space efficient electronic payments. A customer initiates an electronic transaction by transmitting a request for payment information to a seller. In response, the customer receives from the seller the payment information needed to generate an electronic payment. The customer determines the reliability of the payment information by authenticating it. If the payment information is authenticated, then the customer generates an electronic payment using the payment information and a master key unknown to the seller. Finally, the customer transmits the electronic payment to the seller along with a request for desired goods and/or services.
摘要:
Write operations for weakly consistent replicated database systems have application-specific embedded dependency queries and related descriptions of the results that are expected to be returned when the respective dependency queries are run against the database. The dependency queries are arbitrary queries that are provided by the application to satisfy the requirements of the application. Write operations that conflict with the current state of any given instance of such a database are detected by comparing (a) the results that are returned when the dependency queries for those writes are run against the given instance of the database with (b) the results that are expected to be returned.
摘要:
Write operations for weakly consistent replicated database systems have embedded conflict detection and conflict resolution procedures for identifying and resolving, respectively conflicts between such write operations and the current state of any given instance of such a database. These write operations are committed to a firm execution order by the host for one instance of such a database, and this execution order propagates to the other instances of the database. Accordingly, a write log distinguishes between the writes that are known to be committed to a firm execution order (the "tentative writes") is maintained for each instance of the database, thereby enabling the user to explicitly identifying the stable data and the potentially unstable data in any given instance of the database. Furthermore, provision is made for enabling users to select from a set of predefined consistency guarantees across all instances of such a database for any given session.
摘要:
The present invention provides client-selected consistency guarantees to clients of a weakly consistent replicated database on a per "session" basis. The clients have access to utilities which allow the clients to, individually or collectively, define a "session" over which the selected guarantees are enforced. A "session" is broadly defined as a sequence of logically related Reads and Writes to the database. Sessions are initiated and terminated substantially independently of other sessions which may exist concurrently. Clients are allowed, however, to clone sessions and/or merge sessions with other clients. Clients select a minimum relevant subset of guarantees from among a set of pre-defined consistency guarantees, where "relevancy" is a client determined factor. At any given time, the system may be enforcing a number of different combinations of consistency guarantees. The guarantees ensure that all clients participating in a particular session view the database as having certain conditions of data consistency--the consistency of which is only provided with respect to the participants' Read and Write requests. Clients are allowed to downgrade their selected guarantees during the course of their sessions. One implementation of the present invention permits the selection of any one of four consistency guarantees.
摘要:
A system and method for enabling distributed transaction processing by moving all application logic away from the server and into the client by using an optimistic concurrency control framework with client-side transaction validation including virtual full replication under a transactional programming model with full Atomicity, Consistency, Isolation, and Durability (ACID) properties.
摘要:
Schema evolution involves defining flavored object groups. Specifically, related collections of replicated tables and other database objects, which are defined as belonging to an object group, are given different “flavors.” A flavor describes different subsets of the objects and even different subsets of the columns in the master tables. In one embodiment, when one site in a distributed database system propagates changes to a replicated database object, the current flavor for the site is also transmitted, so that the destination site can make the necessary adjustments in the uploaded changes by dropping the values for obsolete columns and using default values for new columns.