Abstract: A method and apparatus for increasing the performance of disk drive access by delaying a pending data transfer operation to an individual disk drive until immediately before the start of the target sector so as to allow servicing of an intervening seek operation to another disk drive.

Abstract: Apparatus for distributing the processing of data across a plurality of loci of control which are connected by a mail system. The apparatus includes a package which contains files of various types and a route specifying the order in which the package is to be circulated among the loci and the processing to be done at each locus. Each locus includes programs executable by users which can manipulate the contents of the package. The programs automatically take the type of file being manipulated into account. The manipulations include modifying the unexecuted portion of the route. Each locus further includes a process which executes the route as modified, a process which tracks the package and receives control commands, and a process which handles errors detected by the other components or by users. The tracking processes maintain data bases for locating the package.

Abstract: Apparatus for determining priority of access to a bus by nodes in a group of nodes attached to the bus. For purposes of determining priority, the apparatus arranges the nodes in a circular configuration and selects one of the nodes as the "anchor node". The anchor node has the highest priority and the priorities of the other nodes are determined by their positions in the circle relative to the anchor node. Each time a device represented by one of the nodes accesses the bus, the current anchor node ceases being the anchor node and the next node in the circle becomes the new anchor node. The priorities of the nodes change to reflect the new location of the anchor node.

Abstract: Method and apparatus are disclosed for use in a digital computer system having a system bus for interconnecting together various agents. A page mode type of memory access provides for the rapid transmission of a block of data across the bus. Blocked refresh circuitry is also employed which disables, if possible, the burst refresh of the memory until a data transfer is completed. A local processor upon an agent having a memory controlled in such manner is provided with a high priority signal line for overriding a current bus transfer for gaining access to the memory. During such a high priority access the blocked refresh circuitry operates in a manner somewhat similar to its operation during the sequential bus transfer, however fewer rows are refreshed during the burst refresh.

Abstract: Apparatus used in a relational data base system to maintain a dependence between a user-defined field in a row of one base table and the state of a set of rows in another base table. There are three kinds of dependent fields: a count field which contains a count of the rows in the set, a sum field which is the sum of a field in the rows of the set, and a base copy down field, which is a field in the rows of the set which contains a copy of a value in a field in the row of the one base table. The two base tables make up a referenced-referencing pair and the row from the one table has a primary key which is used as a foreign key in the set of rows of the other base table. The apparatus consists of components in the data dictionary which define the user-defined dependent field and the nature of the dependence, including any conditions thereon, and components in the data base system's run time system for maintaining the dependence.

Abstract: An office automation system that provides for the incorporation of documents of all types by integrating images into the system. A minicomputer-based system includes applications such as word processing, data base, and mail, each of which can access image documents. Bulk storage of document images is provided using a variety of storage media such as microfilm, microfiche, and optical disks. An image access subsystem provides to each of the office automation applications uniform access to images stored on all of the media. The image access subsystem can use a hardward controller to handle some of the complexity of retrieval of images from the image storage devices. A relational data base system is used to organize the stored images so as to provide flexible access to the images and to isolate any effects of reconfiguration of the image storage system.

Abstract: A distributed reference and change table 36 for a virtual memory system 10 has a number of storage locations at least equal to the maximum number of data blocks of an associated read/write physical memory. A memory module 24 has a plurality of data words organized into n number of data blocks. The memory module includes an integral reference and change table having at least n storage locations each having at least two bits, one bit indicating the occurrence of an access (reference) to a corresponding data block and the other bit indicating if the access was a write (or change) type of access. A plurality of such memory modules are physically and electrically coupled to a common memory carrier module, each of the plurality of memory modules having an integral reference and change table.

Abstract: An expert system shell and expert systems created thereby. The expert system shell creates a knowledge base consisting of terms and their definitions, the definitions making up a hierarchy of definitions in which each definition depends only on definitions at lower levels in the hierarchy or on values obtained from sources external to the knowledge base. The expert system shell creates the knowledge base by asking the expert to define a given term and then asking him to define all undefined terms which appear in the definition of the given term. Because the hierarchy is created in this fashion, the definitions are guaranteed to be complete and non-contradictory. Expert systems created using the expert system shell employ an inferencing engine which determines the value of a given term by evaluating its definition. In the course of the evaluation, the definitions of terms required to define the given term are evaluated and external values required for the evaluation of the definitions are obtained.

Abstract: A tunable operating system in a multiprogrammed data processing system provides improved throughput of tasks blocking on inter-task message requests before time-slice runout. A ready queue subset is defined for each task; the queue subsets for different tasks are overlapped by at least one queue. Dispatch priority is improved when a task requests inter-task message service before time-slice runout, and worsened when a task runs out the time slice. The task is dispatched from a queue in its subset corresponding to the dispatch priority. One of a plurality of time-slice values is assigned when a task is dispatched; the time-slice values are assigned with respect to the position of the task within its queue subset and therefore are not fixed with respect to each queue. The operating system sets the timer to await completion of a full time slice upon each dispatch.

Abstract: An interactive system has a component which manages interactions with the user and a component which manages data transformations. Communication between the interactive component and the data transformation component is by means of a state manager component. The state manager component includes an expected state description, which describes operation of the interactive system as a set of states and transitions therebetween, and an active state description, which describes as much of the present and past state of the interactive system as is required to determine the next state and to "back out" of the present state is response to user inputs specifying "cancel" or "undo" operations.

Abstract: A graphics adapter of the type whose operation is controlled by control data stored therein. The graphics adapter has two sets of loadable control data, one of which is used by a graphics processor in the graphics adaptor and the other of which is used by the processor for the system in which the graphics adapter is used. Because each processor has its own set of control data, control of the graphics adapter is rapidly and easily switched between the processors. Included in the graphics adapter is graphics control apparatus which contains storage for two sets of control data and operates under control of one or the other of them as determined by signals from the graphics adapter. The graphics control apparatus further includes state storage for retaining state necessary for resumption of operation for one processor after the other has used the graphics adapter. The graphics control apparatus can perform both byte and word operations and can emulate byte operations while operating in word mode.

Abstract: A document manager controls the loading into memory from a mass storage means, such as a disk, a document file in disk file format. The loaded document file is stored in memory in document structure format for subsequent access thereto by a task, such as an application program. The loading of the document file into memory may be initiated by a task, either as a result of a user command or as a result of the operation of the task itself. In response to a request to load a document file, the document manager makes a request of a memory manager unit for an assigment of memory space to store the document file. After storage of the document file within the assigned memory space the document manager generates within the memory a document control block descriptive of various parameters associated with the loaded document. The document manager subsequently writes the location within memory of the generated document control block into an assigned location within the task requesting access to the document file.

Abstract: A computer system in which multiple processes may run concurrently includes a window manager for displaying windows associated with different processes. One of the processes represented by a window may be designated as active. Keystrokes are translated by a keyboard driver to events represented by keycodes. The keycodes are routed to processes with which they are associated by reference to a routing table. Unless otherwise indicated, a keycode is routed to the active process. Where a keycode is associated with and transferred to the window manager, subsequent keycodes are stored in a typeahead buffer. The window manager may modify the routing table. After completion of the window manager operation, all keycodes remaining in the buffer are routed to their associated processes as determined by the modified routing table.

Abstract: In a relational database management system, errors can be corrected by an interactive user so that noninteractive operation can continue. A fetch module operates against a cursor to retrieve a record occurrence noninteractively for a selected operation. The selected operation is validated; an error condition can be set. When the selected operation is valid, the operation is performed, and a return signal is provided, causing the fetch module to retrieve the next record occurrence. When the selected operation is invalid, the fetch module responds to the error condition by operating interactively to display the previously retrieved record occurrence with an error message.