10. A computer apparatus, comprising: computer network shared data storage; multiple computers coupled to the computer network shared data storage; a spreadsheet application on at least one of the multiple computers, through which a user can implement a business data model and maintain the business data model in the computer network shared data storage; a computer-based tagging engine which provides a user accessible interface through which a user establishes rules for data of the business data model by tagging data and thereby associating data in at least one cell of a spreadsheet implementing the business data model with at least both an entity dimension tag and a metric dimension tag; a computer based sync engine which ensures that data contents of the business data model stored in the computer network shared data storage reflect a current value for the at least one cell; and a computer based calc engine which is configured to extract data values from the spreadsheet at each cell location corresponding to a location of intersection between a dimension tagged to a column of the spreadsheet and a dimension tagged to a row of the spreadsheet in order to perform at least a period aggregation or an entity aggregation for the data model before storing data of the business data model in the computer network shared data storage.
13. The computer apparatus of claim 10 , wherein the location of intersection is to the left of row-assigned dimension tags and above column-assigned dimension tags.