Abstract: Based on the author's previous research at data quality propagation for relational database, the paper sumed up and presented a data quality model at attribute granularity, which both considers the influence of accuracy and completeness. According to the model, the tuples were classified into five categories. The definitions of accuracy and completeness both include the influence of the data item and tuple. After analysing the null data neither correct nor complete, the mutual relationship between them was formed. Then the attribute error rate before and after quantitative was introduced to define metrics further.

Key words: Data quality, Quality model, Accuracy, Completeness, Relational database