Abstract: In order to manage a plurality of sets of multidimensional data positioned in a specific area of a computer, when hierarchically dividing a first area within the specific area into second areas that are to constitute child areas thereof, a decision is made as to whether or not a division condition, which is based upon the state achieved when the sets of multidimensional data are allocated to the first area and the state achieved when the sets of multidimensional data are allocated to the second areas, is satisfied. When it is decided that the division condition will be satisfied, the first area is hierarchically divided into the second areas to allocate the sets of multidimensional data to the second areas.

Abstract: A production control is applied to control a production machine for producing a product from a material in a process divided into a plurality of steps. The execution numbers are counted on a per-step basis. A priority order is allocated on the basis of the counted execution numbers. The information relating to the priority order is output to the production machine. The production machine can select the next step in accordance with the input priority order. The execution numbers can be properly controlled by such control method on the per-step basis.

Abstract: A data retrieval system which updates data quickly. A divider determines the first substring and second substring based on the code string from which a key string is retrieved. For each substring, a generator generates the dictionary data showing the correspondence between a trailing string, which is a trailing part of data in the substring, and the start position of the trailing string within the code string. A retriever a trailing string whose leading string is a key string or a part of the key string, based on the dictionary data. A remover removes duplicate trailing strings. When a changer changes the code string, an updater updates dictionary data associated with the substring based on the contents of the change. A first maintaining device maintains the boundary interval at a maximum key length or longer, and a second maintaining device maintains the boundary interval at a specified length or less.

Abstract: A contention-type data communication system such as an optical star-configured network comprises a plurality of stations connected with one another through data bus. To detect a signal collision quickly, each of the stations is arranged to transmit a collision-detecting packet which has a predetermined time length T.sub.1 and a predetermined pulse pattern, and then transmit a data packet after a time interval T.sub.2. The number or pattern of pulses received during a time period T.sub.1 +T.sub.2 from the start of reception of a collision-detecting packet is compared with that of the self-transmitted collision-detecting packet so that the signal collision is detected when noncoincidence occurs.