Brent Alphonzo Welch

US Patent:

53411552, Aug 23, 1994

Filed:

Apr 6, 1992

Appl. No.:

7/864271

Inventors:

Scott A. Elrod - Redwood City CA
Brent B. Welch - Mountain View CA
David Goldberg - Palo Alto CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

G09G 302

US Classification:

345179

Abstract:

In a large area display system, multiple persons may work together with multiple input devices for supplying and receiving information in an interactive system with a single large area display. The large area display system comprises a screen wherein computer generated information is projected upon one side of the screen, and users interact with the computer from the opposite side of the the screen. Data coordinates for an input device corresponding to a pseudo image sensed by the receiving subsystem electronics are provided to the controlling computer. The input data coordinates from the pseudo image are normalized for variations due to frequency dependence and electronic drift. The normalized data coordinates are looked up in a calibration table to account for distortion in the pseudo image detection electronics. Screen coordinates corresponding to pixel locations on the large area screen are found by interpolation from the data From the calibration table. The calibration table is prepared off-line, based on a bicubic spline interpolating function which is then compressed using a delta compression scheme.

US Patent:

55817530, Dec 3, 1996

Filed:

Sep 28, 1994

Appl. No.:

8/314971

Inventors:

Douglas B. Terry - San Carlos CA
Alan J. Demers - Boulder Creek CA
Karin Petersen - Menlo Park CA
Michael J. Spreitzer - Tracy CA
Marvin M. Theimer - Mountain View CA
Brent B. Welch - Mountain View CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

G06F 1300

US Classification:

395617

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. 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.

US Patent:

54856345, Jan 16, 1996

Filed:

Dec 14, 1993

Appl. No.:

8/166478

Inventors:

Mark D. Weiser - Palo Alto CA
Richard J. Goldstein - San Francisco CA
Roy Want - Mountain View CA
Brent B. Welch - Mountain View CA
Scott A. Elrod - Redwood City CA
David A. Maltz - Mountain View CA
William N. Schilit - Palo Alto CA
Marvin M. Theimer - Mountain View CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

H04B 138
H04B 1700

US Classification:

455 531

Abstract:

A system is provided for servicing requests by a mobile controller to utilize stationary or mobile resources present within a partitioned communication cell such as an office or room in a building. The mobile controller has a control signal mechanism for generating control request signals to modify behavior of the stationary or mobile resource, with the range of the control request signals substantially limited to the partitioned communication cell. A room agent receives and acts upon the control request signals after dynamically determining availability of both mobile resources entering and exiting the partitioned communication cell and stationary resources already present in the partitioned communication cell. In operation, the room agent is configured to grant requests for utilization of mobile and stationary resources located within the partitioned communication cell when predetermined contextual attributes within the partitioned communication cell are consistent with previously specified interaction policies.

US Patent:

55817548, Dec 3, 1996

Filed:

Dec 7, 1994

Appl. No.:

8/352012

Inventors:

Douglas B. Terry - San Carlos CA
Marvin M. Theimer - Mountain View CA
Alan J. Demers - Boulder Creek CA
Karin Petersen - Menlo Park CA
Michael J. Spreitzer - Tracy CA
Brent B. Welch - Mountain View CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

G06F 720
G06F 1730

US Classification:

395608

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.