Xerox Corporation

Fuji Xerox Corporation

Jennifer D Thomas

David P Nesbitt

Steve Atsushi Okamoto

Sang W Kim

Joseph Z Fung

Vikram R Mahuvakar

Nobuyuki Takao

Charles H Evans, Iv

Gilbert K K Leong

Temporary states are used transitionally in run-time situations and are unknown to the object database. A temporary state is created if, when an object is performing a requested event, interim work needs to be performed before the object reaches a permanent destination state. Use of a temporary state is transparent to the caller of the requested event.

State based object transition control and nested locking

A document printing system involves multi-threaded processing of a document object. A deadlock situation between a preprocessing thread and a cancellation thread can be averted with a time-out locking mechanism. After the cancellation thread has locked the document object, its sets a cancel flag, then waits for preprocessing to complete. Meanwhile, the preprocessing thread may request a lock of the document object. If so, it will specify a maximum time-out period. After expiration of the time-out period, a timed-out status response will be sent from the document object to the preprocessing thread. The preprocessing thread will then poll the document object for a cancel flag. A cancel flag will be set on the document object only if the cancellation thread has requested the document object perform a cancellation operation. If there is no cancel flag, the preprocessing thread will again request a lock of the document object with a maximum time-out period. If there is a cancel flag, the preprocessing thread will send a cancellation complete signal to the document object.

Avoiding deadlock situations in a printing system using a locking time-out mechanism

Temporary states are used transitionally in run-time situations and are unknown to the object database. A temporary state is created if, when an object is performing a requested event, interim work needs to be performed before the object reaches a permanent destination state. Use of a temporary state is transparent to the caller of the requested event. Within a single flow of control, an unlimited number of nested locks may be acquired. A request to unlock an object will only truly unlock the object if the unlock requester is at the highest level of locking. For recursive or embedded functions, no knowledge of the previous locking condition is necessary. Attribute-based locking provides a mechanism for allowing only certain members of the system to lock an object for writing while the object is in a predetermined state. However, any thread may obtain a read lock on an object in order to examine its attributes. This may be expanded to state that the system may restrict locking of an object or entity based upon any attribute in the database or upon any combination or logical expression of these attributes.

State-based object transition control and nested locking

A filter interface allows a filter to send extracted attribute information extracted from the master document data to a server. The server then stores the received attribute information into an attribute database.

Filter interface for managing printer system information

State-based object transition control and attribute-based locking

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Hermosa Beach, CA, United States of America

Jennifer D Thomas