Echelon Systems Corporation

Compaq Computer Corporation, Inc.

Marek J Fridrich

Glen Meyers Riley

Robert A Dolin

Harry Anthony Leslie

Awny K Al-omari

The present invention applies one or more pruning heuristics to the expression, the binding, and/or the substitute during a database query optimization process. The heuristics identify certain rules that can be eliminated by either not applying the rules and/or not implementing the rules for a given expression and context (if any) based upon one or more flow rates of the expression. The pruning heuristics can eliminate the application of rules based upon the flow rates of the binding or substitute, for example. Examples include (1) not applying (cutting) a MergeJoin rule for a join expression when an inner table is small enough to be stored in a memory space that is allocated for a HashJoin; (2) not applying implementation rules on the substitute of a left-shift rule for an expression if the resulting input data flow rate from the left child of the join is significantly larger in the substitute than in the binding; (3) not applying the join to TSJ (tuple substitute join) rule if the data flow output of the join expression is significantly larger than the data flow input from the inner child of the join expression; or (4) not applying implementation rules on the substitute join expression of a left shift rule if the number of cross products increases and if the data flow rate from the left child is increases.

System and method for reducing compile time in a top down rule based system using rule heuristics based upon the predicted resulting data flow

An improved network for communication of message packets. The network of the present invention implements an improved collision avoidance, detection and backoff system for communication on a media between nodes. The apparatus calculates a time period P after detecting the media is idle using a formula F which is a function of a pseudo-random delay factor T. If the media remains idle during the time period P, the device may transmit a message. The apparatus further has the ability to assign messages as being either priority or non-priority messages. Priority messages may be transmitted during priority message slots preassigned to transmitting nodes. Non-priority message contend for the media during a period of time following the period set for transmission of priority messages.

Multiaccess carrier sensing network communication protocol with priority

An improved network for communication of message packets. The present invention provides for improved reliable multicast messaging wherein messages may be reliably multicast to members of a multicast group and acknowledgements may be handled in an improved and efficient manner. In particular, a message may be transmitted to all members of a group, each member of the group responding to receipt of the message with an acknowledgement message. Further, facility is provided to allow for transmissions of reminder messages in the event one or members of a group do not respond to a message with an acknowledgement.

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San Jose, CA, United States of America

Marek J Fridrich