This is an introduction to a proposed Extensible Markup Language (XML) standard for exchanging warehouse data between networked systems. To be more precise, XCube is an open, manufacturer-independent, XML-based family of document templates for storing, exchanging, and querying data warehouse data (data cubes).

XCube is organized into a number of separate modules. The modules refer to concepts that are well defined and understood in the data warehouse field: multidimensional schema, descriptions of the single dimensions, and fact data (XCubeSchema, XCubeDimension, and XCubeFact). The authors also introduce two kinds of document type, XQuery and XFunction, for dynamically exploring the content of another warehouse.

These formats are primarily meant to reduce the amount of data transferred over the network, but in the end can also be seen as excellent groundwork for the conceptual modeling phase of new data warehouses.

The paper opens with some use cases, encountered in the real word by people accessing data warehouses, and enumerates their advantages and disadvantages. It continues with a discussion of the requirements for representing online data cubes. Some of these are general and valid with any standard, while others are particular to decision support systems. Readers will also find a very short critique of related work.

The core of the paper is a description of the primary proposed formats: XCubeSchema, XCubeDimension, and XCubeFact. However, this is an introduction rather than a complete description of the formats. References are made to the formal and complete proposed standards. A simple and clear request/response model is used to exemplify getCubeSchema, getClassSchema, getDimensions, and other operations carried over a network.

Readers should appreciate the openness of the authors in drawing attention to the limitations of their proposed schema. For example:

The functionality of getFacts is rather similar to the OLAP [online analytical processing] operations slice [and] dice. But it is important to know that these restrictions can only be applied to the basic granularity of the cubes; roll-up or drill-down operations are not supported. XCube is not meant to be another OLAP dialect but only a data format for exchanging multidimensional data over the network.

In conclusion, this is a well-written and valuable paper, covering the current trend of using XML in the decision support field.