Abstract: High availability is achieved in a multiprocessor system by grouping the processors into two clusters operating on different clock and power boundaries. In each cluster is an array containing a substantially identical copy of the system information relating to the operation of the processors. Each processor has a local port for accessing the local array and a remote port for accessing the remote array. When an update is made on the system information, it is made on both the local and remote arrays with the remote update performed transparently.

Abstract: In a searching for library documents that match the content of a given sequence of query words, a set of equivalent words are defined for each query word along with a corresponding word equivalence value assigned to each equivalent word. Target sequences of words in a library document which match the sequence of query words are located according to a set of matching criteria. The similarity value of each target sequence is evaluated as a function of the corresponding equivalence values of words included therein. Based upon the similarity values of its target sequences, a relevance factor is then obtained for each library document.

Abstract: A voltage controlled oscillator (VCO) having high temperature stability and wide voltage/frequency linearity is provided. The VCO comprises a multivibrator being switched by a bipolar type device, and temperature fluctuations of the bipolar type means are compensated by a FET current source coupled thereto. To provide a linear relationship of frequency vs. voltage over wide voltage range, the bipolar device is further regulated by a plurality of resistor and diode networks.

Abstract: An edge-triggered latch is disclosed which has a low setup time and almost no metastability problem. It comprises a dynamic sensing means for detecting the voltage level of the data signal and at least one dynamic buffer for amplifying said detected voltage level into one of two logic levels recognizable by a static latch wherein the sampled result is stored.

Abstract: To increase storage capacity of a disk storage device, the recording surface of the device is partitioned into a plurality of concentric recording bands, data to be recorded on respective bands are encoded using different run-length-limited codes with the code rate of each band being higher than the adjacent inner band.

Abstract: An improved method is described for transmitting facsimiles of scanned symbols. Prototype facsimiles of each symbol in a library are enhanced by averaging the representations of each scanned symbol with a respective previously created prototype facsimile for that symbol. The amount of white space at opposite sides of each symbol prototype is determined. The enhanced prototype facsimile for each scanned symbol is associated with positional parameters denoting the average white space at said opposite sides of each symbol.

Abstract: A method is disclosed for maintaining availability of a restartable data base system where continuity of service is guaranteed by having a loosely-coupled backup processor taking over processing of a degraded active processor. The backup processor continuously tracks the activities of the active processor to ascertain data set elements updatable by the active processor. Upon switchover, images of data set elements updatable by the degraded active processor are created in the buffer of the backup processor. By making references and updates to the images, processing of the backup processor can start immediately after switchover. Upon preventing the degraded active processor from making further updates, the backup processor writes the images back to the data base.

Abstract: This invention relates to method and apparatus for compressing multilevel signals. The compression is based upon prediction errors and probability distributions. Compression is improved by conditioning the probability distributions using context of previous events. Storage required for storing the probability distributions is reduced by partitioning the prediction errors into predetermined ranges which become the coding events and contexts. Compression is made efficient with a partition which is a function of the sign and the number of significant bits in the prediction errors.

Abstract: A method for removing noise in the form of small black spots in a black and white raster picture, which includes the following steps: Generating a moving window of 5.times.5 picture elements having an inner window (R1) of nine and a surrounding outer window (R2) of sixteen picture elements; detecting for each such window whether there are more black picture elements in the inner window than a given threshold, or whether there is any connection between black picture elements in the inner window and the outer window; if this is true, leaving the inner window unchanged; otherwise, i.e. if there are less black picture elements in the inner window than the threshold, and if they are not connected to black picture elements in the outer window, making the inner window all white. Thus, isolated small black spots are eliminated without eroding edges or erasing very thin lines.

Abstract: A system for controllably varying the width of the data window in a magnetic storage device to perform comparative data detection error rate measurements thereon is provided. The system generates the programmably and continuously variable stressed data window symmetrically within, and in locked phase with, the full data window under the control of a single current DAC in the VCO of the device.

Abstract: In assigning features to nodes of a tree structured classifier and determining terminal nodes in response to a training set of objects each being determined by a plurality of features, a selected characteristic, such as a cost function based on the minimum description length, of the plurality of features unused at prior nodes is determined along the path from the root to the present node, a feature is then assigned to the node having a preferred value for the selected characteristic relative to the other features. Child nodes of the node are created in response to the assigned feature with features assigned thereto in a similar way. The preferred values for the selected characteristics of the assigned features for the child nodes of the node are combined and compared with the preferred value of their father node. Classification of the father node as a terminal is based upon such a comparison.

Abstract: In a distributed processing system network in which at least one node operates as a source location having access to data objects of a database, and at least one other node operates as a replica location storing replicas of data objects from the source location, managing obsolescence of the replicas is performed by having the replica locations submitting requests to the source location for ascertaining obsolescence of data objects. The source location, responsive to a request from a requesting replica location, extracts identifiers of a set of obsolete objects and communicates them to the requesting replica location. Upon receiving the identifiers, the requesting location renders inaccessible those data objects corresponding to the identifiers received. The source location then removes those identifiers that have been communicated to the requesting replica location.

Abstract: In a distributed processing system having a source node accessing data objects from a database and a replica node storing replicas of requested source data objects received from the source location, the impact to replicas caused by a change in a source data object is calculated by assigning a version number to the change. An identifier of the portion of the source database affected by the change is generated, as well as a list of replicas containing objects from the affected portion of the database. For a replica location communicating with the source location, a table of the replicas from the list is then recorded along with the version number for communicating to the replica location.

Abstract: Method and apparatus for magnetoresistive (MR) head biasing and output signal detection for reading data recorded in magnetic media. The MR head may be biased by constant current or constant voltage, and an output signal, proportional to the ratio of the instantaneous value of the change in MR head resistance to total MR head resistance when exposed to the magnetic field of the media, is detected.

Abstract: A system for correcting errors in data read from a direct access storage device employs an extendable, two-level coding scheme having n subblocks in a relatively long variable-length block of data, each subblock having up to m bytes of data. At the subblock level, decoding capability provides correction of up to t.sub.1 errors and detection of up to t.sub.1 +c errors in each subblock, while the block-level decoding capability provides correction of up to t.sub.2 errors in any one of the subblocks. The combined capability of the system corrects any combination of (t.sub.1 +x) errors in one subblock, and up to t.sub.1 errors in any or all of the other subblocks in the block, where x is a non-negative integer such that (t.sub.1 +x).ltoreq.t.sub.2 and x<c. The combined capability of the system also provides correction of any combination of (t.sub.1 +x) errors in one subblock and up to (t.sub.1 +C-x) errors in any or all of the other subblocks in the block, where x is an integer such that (t.sub.1 +x).ltoreq.

Abstract: Improved design, computation and implementation of pairs of error detection check bytes, where such bytes are appended to the end of a variable length record for data integrity check of the entire record after ECC correction, is provided. The error detection check bytes are each computed using different powers of the same companion T matrix of a degree-eight primitive polynomial used for computing associated ECC check bytes. Use of the same T matrix provides the computational convenience of a reasonable size Galois field of GF(2.sup.8), while providing long cycle length through a recurring offset within the data sequences corresponding to two members of each pair.