A database network system is capable of recognizing in a short time (within several minutes) the state of damage or the like of city lifelines (waterworks, electricity, and gas supplies) over a whole city. A database network system according to the present invention includes a center station, relay database stations (RDSs), and terminal stations. A terminal station group includes a plurality of terminal stations for acquiring changing information to accumulate the information as data and for transmitting the data as requested. Each of the plurality of relay database stations (RDSs) is arranged for the terminal station group, and accumulates pieces of information sequentially received from the terminals as specific data and other data and transmits the data as requested. The center station sequentially receives parts of the specific data and other data of an arbitrary one of the relay database stations (RDSs) from the corresponding relay database station, performs a receiving operation of all the data and the specific information data a plurality of times by performing the receiving operation a plurality of times, and accumulates the data as needed.
Querying databases includes receiving a query for information, the query including a common identifier for a plurality of collections of data and indicating whether a result of the query may include a null result, searching each of the collections of data for the information, and considering a speed of each of the collections of data in performing the searching.
A method of detecting the location of a failure (e.g., a sudden leak) in a fluid pipeline network, which can be suitably used for estimation of the location of a failure in a water pipeline network, includes the steps of periodically measuring a flow rate or fluid pressure with sensors arranged at a plurality of measuring points along a pipeline in a water pipeline network; comparing a latest measured amount and a previous measured amount at each measuring point to determine if an amount of change at an arbitrary point has exceeded a predetermined value; and calculating a position at which an amount of change becomes maximum, the position being calculated from the magnitudes of the amounts of changes in respective measured values at the time of the detection. The pipeline network may be a water supply and distribution pipeline network which includes a trunk pipeline and branch pipelines.
