Abstract: Use of a policy object for verification in a distributed system. A machine downloads a policy object containing a reference to code governing verification of data. The machine uses the reference to obtain the code and locally verify data or other information. As particular rules for the data change, the policy object may be updated to provide a reference to the code for the new rules when it is downloaded.

Abstract: Event notification in a distributed system using an object maintained in serialized form, referred to as a marshalled object. For event notification, a machine registers with a device to receive notification of particular events within a network, and a marshalled object is transmitted with a registration request.

Abstract: A method and system for leasing storage locations in a distributed processing system is provided. Consistent with this method and system, a client requests access to storage locations for a period of time (lease period) from a server, such as the file system manager. Responsive to this request, the server invokes a lease period algorithm, which considers various factors to determine a lease period during which time the client may access the storage locations. After a lease is granted, the server sends an object to the client that advises the client of the lease period and that provides the client with behavior to modify the lease, like canceling the lease or renewing the lease. The server supports concurrent leases, exact leases, and leases for various types of access. After all leases to a storage location expire, the server reclaims the storage location.

Abstract: A method and system for transmitting objects in an object-oriented distributed system allows the reconstruction of objects and downloading of code associated with such object reconstruction to be deferred until it is needed by a program. The deferred reconstruction is accomplished by using a Java object called a “marshalled object,” which is a self-describing stream and which is a first-class entity in the system, meaning that it exists within a type system of a programming language and can be accessed and manipulated by instructions written in that language. Such an object can typically be produced by any object that can be passed from one address space to another, and it can be stored, passed to other objects, or used to reconstruct an object of the original type on demand. The reconstruction of an object is deferred until the code holding a marshalled object directly calls the creation of the object using the marshalled object.

Abstract: A system for using a lease to detect a failure and to perform failure recovery is provided. In using this system, a client requests a lease from a server to utilize a resource managed by the server for a period of time. Responsive to the request, the server grants the lease, and the client continually requests renewal of the lease. If the client fails to renew the lease, the server detects that an error has occurred to the client. Similarly, if the server fails to respond to a renew request, the client detects that an error has occurred to the server. As part of the lease establishment, the client and server exchange failure-recovery routines that each invokes if the other experiences a failure.

Abstract: A method and apparatus is provided for enabling blocked remote methods to relinquish threads and other resources to other methods on a server system. In a distributed computing environment, remote methods are allocated numerous network resources but are blocked while they wait for operations, such as a write operation from another process, to complete. When enough remote methods are blocked, threads and other network resources may run out. Client systems requesting server services may experience slower response times. This method and system provides a technique for remote methods to relinquish network resources, such as threads, for other methods to use while the methods are blocked. Once the conditions causing the remote methods to block is resolved, the remote methods continue execution. This technique enables high volume client-server transaction systems to utilize threads and other resources in a distributed computing environment more efficiently.

Abstract: An improved lookup service is provided that allows for the dynamic addition and deletion of services. This lookup service allows for the addition and deletion of services automatically, without user intervention. As a result, clients of the lookup service may continue using the lookup service and its associated services while the updates occur. Additionally, the lookup service provides a notification mechanism that can be used by clients to receive a notification when the lookup service is updated. By receiving such a notification, clients can avoid attempting to access a service that is no longer available and can make use of new services as soon as they are added to the lookup service.

Abstract: A database system wherein one or more entry databases store a plurality of entries. Each entry is of a given type that defines the fields of the entry. Each field contains or identifies an object with associated attributes or data. The type of each entry may further define behavior in the form of methods the entry can implement. An entry type which is a subtype of another inherits all fields and behavior of its super-type, and contains additional fields and/or defines new/modified behavior. Entries may be expressed in a Java™ programming language. The database system may further employ a search engine which allows queries to be made upon entries in the database. In one implementation, the queries include a read operation, a take operation, and a notify operation. Each query request includes a command indicating the type of operation, and a template which is an entry object having some or all of its fields set to specific values that must be matched exactly.

Abstract: A method implemented by a computer-based electronic assistant to receive and manage incoming calls to a subscriber including the steps of receiving an incoming call to the subscriber from a caller; establishing a first connection between the electronic assistant and the caller; establishing a second connection between the electronic assistant and the subscriber; over the second connection, electronically notifying the subscriber of the incoming call; in response to receiving a call accept command from the subscriber over the second connection, linking the caller and the subscriber so that they may communicate with each other; upon linking the subscriber to the caller, switching the electronic assistant to a background mode in which said electronic assistant continues to monitor the subscriber over the second connection while the subscriber is linked with the caller; and in response to receiving a summoning command, switching the electronic assistant into a foreground mode, wherein the electronic assistant whe

Abstract: A database system wherein one or more entry databases store a plurality of entries. Each entry is of a given type that defines the fields of the entry. Each of the fields contains or identifies an object with associated attributes or data. The type of each entry may further define behavior in the form of methods the entry is configured to implement. An entry type which is a subtype of another inherits all of the fields and behavior of its supertype, and contains additional fields and/or defines new/modified behavior. Entries may be expressed in a Java.TM. class of the Java.TM. programming language. The database system may further employ a search engine which allows queries to be made upon entries in the database. In one implementation, the queries include a read operation, a take operation, and a notify operation. Each query request includes a command indicating the type of operation, and a template which is an entry object having some or all of its fields set to specified values that must be matched exactly.

Abstract: A method implemented by a computer-based electronic assistant to receive and manage incoming calls to a subscriber including the steps of receiving an incoming call to the subscriber from a caller; establishing a first connection between the electronic assistant and the caller; establishing a second connection between the electronic assistant and the subscriber; over the second connection, electronically notifying the subscriber of the incoming call; in response to receiving a call accept command from the subscriber over the second connection, linking the caller and the subscriber so that they may communicate with each other; upon linking the subscriber to the caller, switching the electronic assistant to a background mode in which said electronic assistant continues to monitor the subscriber over the second connection while the subscriber is linked with the caller; and in response to receiving a summoning command, switching the electronic assistant into a foreground mode, wherein the electronic assistant whe