An information system to which a data generation device that generates site data as to plural tasks included in a process and a storage device that stores the site data generated by the data generation device are coupled, the information system characterized in that it is adapted to execute: generating, for each of the tasks, definition information that defines a) a plurality of task association information that classify the site data, b) task information that defines task content of itself and association with another task, and c) extension information being a storage area for storing information with a high utilization rate selectively in advance is set in the definition information in advance so that the information with the high utilization rate can be quickly acquired, wherein the task association information includes at least one of worker information, machine information, material information, and work procedure information, each associated with the task information, wherein the task information and each of the task association information are associated with each other by relation information created from the definition information; and generating, for each of the tasks, association data that includes access information to the site data stored in the storage device on the basis of the definition information; executing storing the association data; and searching the stored association data for a second information derived from a second task of the plural tasks associated to a first information derived from a first task of the plural tasks, wherein the system further comprising: a user interface unit that displays a connection relation of the plurality of the task association information associated with each other by the association data, wherein the information system is further adapted to execute: searching, on the basis of the association data, for the second information associated with the first information that is selected from the connection relation displayed and displaying the first information and the second information on the user interface unit with the connection relation of the plurality of the task association information. generating, for each of the tasks, definition information that defines a) a plurality of task association information that classify the site data, b) task information that defines task content of itself and association with another task, and c) extension information being a storage area for storing information with a high utilization rate selectively in advance is set in the definition information in advance so that the information with the high utilization rate can be quickly acquired, wherein the task association information includes at least one of worker information, machine information, material information, and work procedure information, each associated with the task information, wherein the task information and each of the task association information are associated with each other by relation information created from the definition information; and generating, for each of the tasks, association data that includes access information to the site data stored in the storage device on the basis of the definition information; executing storing the association data; and searching the stored association data for a second information derived from a second task of the plural tasks associated to a first information derived from a first task of the plural tasks, wherein the system further comprising: a user interface unit that displays a connection relation of the plurality of the task association information associated with each other by the association data, wherein the information system is further adapted to execute: searching, on the basis of the association data, for the second information associated with the first information that is selected from the connection relation displayed and displaying the first information and the second information on the user interface unit with the connection relation of the plurality of the task association information. searching, on the basis of the association data, for the second information associated with the first information that is selected from the connection relation displayed and displaying the first information and the second information on the user interface unit with the connection relation of the plurality of the task association information.