A data processing system comprising: a storing unit configured to store ontology data of a work procedure manual relating to a product assembly; a selection unit wherein the selection unit includes: a receiving section configured to receive a query; an acquisition section configured to acquire the ontology data from the storing unit; an inferring section configured to use the query and the ontology data to infer key information of a key/value format based on a point in time and a sensor ID corresponding to the query and the ontology data; and a selecting section configured to select a data stream based on the query, wherein the data stream includes the key information inferred from the query, the data stream being a data stream among data streams each including key information uniquely given to sensor data relating to the product assembly; and a processing unit configured to process RAW data of the selected data stream by converting the RAW data into data capable of being subjected to inference processing, wherein the processing unit includes: a data window segmentation module configured to sequentially set a window on the selected data stream while moving the window on a time axis; an abstracting section configured to abstract the selected data stream by performing frequency component extraction or data averaging on the data within the window; a structuring section configured to structure the abstracted data stream into multi-part RDF data; and a processing section configured to use product assembly sequence information of the structured data stream from the sensor data relating to the product assembly and product assembly sequence information obtained from the ontology data to detect a failure of the product assembly. a storing unit configured to store ontology data of a work procedure manual relating to a product assembly; a selection unit wherein the selection unit includes: a receiving section configured to receive a query; an acquisition section configured to acquire the ontology data from the storing unit; an inferring section configured to use the query and the ontology data to infer key information of a key/value format based on a point in time and a sensor ID corresponding to the query and the ontology data; and a selecting section configured to select a data stream based on the query, a receiving section configured to receive a query; an acquisition section configured to acquire the ontology data from the storing unit; an inferring section configured to use the query and the ontology data to infer key information of a key/value format based on a point in time and a sensor ID corresponding to the query and the ontology data; and a selecting section configured to select a data stream based on the query, wherein the data stream includes the key information inferred from the query, the data stream being a data stream among data streams each including key information uniquely given to sensor data relating to the product assembly; and a processing unit configured to process RAW data of the selected data stream by converting the RAW data into data capable of being subjected to inference processing, wherein the processing unit includes: a data window segmentation module configured to sequentially set a window on the selected data stream while moving the window on a time axis; an abstracting section configured to abstract the selected data stream by performing frequency component extraction or data averaging on the data within the window; a structuring section configured to structure the abstracted data stream into multi-part RDF data; and a processing section configured to use product assembly sequence information of the structured data stream from the sensor data relating to the product assembly and product assembly sequence information obtained from the ontology data to detect a failure of the product assembly. a data window segmentation module configured to sequentially set a window on the selected data stream while moving the window on a time axis; an abstracting section configured to abstract the selected data stream by performing frequency component extraction or data averaging on the data within the window; a structuring section configured to structure the abstracted data stream into multi-part RDF data; and a processing section configured to use product assembly sequence information of the structured data stream from the sensor data relating to the product assembly and product assembly sequence information obtained from the ontology data to detect a failure of the product assembly.