Abstract: 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.

Abstract: Techniques for making a replica of a particular group of database objects of a database on a particular node that does not initially have the particular group of database objects include determining whether conditions for copying a full database from a first node are satisfied. If conditions for copying the full database from the first node are not satisfied, then a database-object-copy routine is employed for each database object in the particular group of database objects. If conditions for copying the full database from the first node are satisfied, then a full-database-copy routine for performing a copy of an entire database is employed.

Abstract: 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.

Abstract: 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.

Abstract: Techniques for making a replica of a particular group of database objects of a database on a particular node that does not initially have the particular group of database objects include transferring description data from a first node to the particular node during a first time period. The description data describes the particular group of database objects at a first time. The first time period begins at the first time and ends at a second time. During the first time period, a request from a user of the database to perform an operation involving particular data in the particular group of database objects is processed.

Abstract: A method for applying changes to a standby system is described in which multiple apply tasks or “slaves” are scheduled to changes from redo logs, especially those changes in large transactions, in parallel and as soon as they are encountered in the logs. To foster data convergence, a partial ordering may be imposed on the transactions so that those transactions that actually depend on others are forced to wait on the transactions they are dependent upon commit. To foster read consistency, synchronization points may be periodically established, at which points a read consistent state of the standby database system can be obtained-all without adversely impact the throughput of the system.

Abstract: Replication for front office automation involves the use of snapshots that are instantiated on laptops, in which refreshing the snapshots is driven from a master site with a high-performance protocol. All of the necessary snapshot metadata for performing the snapshot refreshes is stored at the master site, so that the laptop only needs to send a single refresh request. In response to the refresh request, the master site reconciles the differences between the master tables and the laptop's snapshots and transmits the differences to the laptop, reducing the necessary network traffic for updating a snapshot to a single round trip.

Abstract: Replication for front office automation involves the use of snapshots that are instantiated on laptops, in which refreshing the snapshots is driven from a master site with a high-performance protocol. All of the necessary snapshot metadata for performing the snapshot refreshes is stored at the master site, so that the laptop only needs to send a single refresh request. In response to the refresh request, the master site reconciles the differences between the master tables and the laptop's snapshots and transmits the differences to the laptop, reducing the necessary network traffic for updating a snapshot to a single round trip.

Abstract: 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.

Abstract: A method of verifying electronic payments generated using a key unknown to the verifier. In anticipation of accepting electronic payments, a seller requests and receives from a bank a conversation key and a first set of electronic verifiers for a first set of electronic payments from a customer. Each verifier allows authentication of an associated electronic payment without revealing the private key used by the customer to generate the electronic payments. Prior to initiating a transaction or series of transactions, the customer requests payment information from the seller for use, along with the master key, in generating electronic payments Afterward, when the customer pays with an electronic payment, the seller authenticates the electronic payment using one of the verifiers. The seller responds to the buyer's request if the electronic payment is authenticated.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A method of generating electronic monetary tokens that supports off-line transactions while preventing double-spending. Generation of electronic token halves by a financial services provider begins in response to a request from a buyer to generate electronic monetary tokens to be used with an identified seller. First, the financial services provider generates a multiplicity of electronic monetary tokens. Second, the provider splits each electronic monetary token into two electronic token halves and associates with each the same serial number. These electronic token halves when combined recreate the electronic monetary token from which they were generated, but by themselves neither electronic token half has any value. Nor can either electronic half by itself be used to create the electronic monetary token without the token half's mate.

Abstract: 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.

Abstract: Write operations for weakly consistent replicated database systems have embedded application-specific merge procedures that are invoked for resolving conflicts whenever it is found that the related write operation conflicts with the current state of a given instance of such a database. The effect of executing such a merge procedure is deterministic for any state of the given instance of the database happens to be in when the merge procedure is executed.

Abstract: 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.

Abstract: 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.

Abstract: A write log that distinguishes between write operations that are known to be in a stable write order ("committed writes") and write operations that still are in a potentially unstable write order ("tentative writes") are maintained for each instance of a weakly consistent replicated database so that the stable and the potentially unstable data in any given instance of such a database can be explicitly identified.

Abstract: 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.