This subclause introduces the overall form of a SpreadsheetML package, and identifies some of its main element types. (See Part 3 for a more detailed introduction.)

A SpreadsheetML package has a relationship of type officeDocument, which specifies the location of the main part in the package. For a SpreadsheetML document, that part contains the workbook definition.

A SpreadsheetML package’s main part starts with a spreadsheet root element. That element is a workbook, which refers to one or more worksheets, which, in turn, contain the data. A worksheet is a two-dimensional grid of cells that are organized into rows and columns.

The cell is the primary place in which data is stored and operated on. A cell can have a number of characteristics, such as numeric, text, date, or time formatting; alignment; font; color; and a border. Each cell is identified by a cell reference, a combination of its column and row headings.

Each horizontal set of cells in a worksheet is called a row, and each row has a heading numbered sequentially, starting at 1. Each vertical set of cells in a worksheet is called a column, and each column has an alphabetic heading named sequentially from A–Z, then AA–AZ, BA–BZ, and so on.

Instead of data, a cell can contain a formula, which is a recipe for calculating a value. Some formulas—called functions—are predefined, while others are user-defined. Examples of predefined formulas are AVERAGE, MAX, MIN, and SUM. A function takes one or more arguments on which it operates, producing a result. For example, in the formula SUM(B1:B4), there is one argument, B1:B4, which is the range of cells B1–B4, inclusive.

Other features that a SpreadsheetML document can contain include the following: comments, hyperlinks, images, and sorted and filtered tables.

A SpreadsheetML document is not stored as one large body in a single part; instead, the elements that implement certain groupings of functionality are stored in separate parts. For example, all the data for a worksheet is stored in that worksheet's part, all string literals from all worksheets are stored in a single shared string part, and each worksheet having comments has its own comments part.