The Research Of ROLAP Algorithms

Online Analytical Processing (OLAP) means analysing large quantities of data in real-time. Unlike Online Transaction Processing (OLTP), where typical operations read and modify individual and small numbers of records, OLAP deals with data in bulk, and operations are generally read-only. The term 'online' implies that even though huge quantities of data are involved—typically many millions of records, occupying several gigabytes—the system must respond to queries fast enough to allow an interactive exploration of the data. As we shall see, that presents considerable technical challenges.OLAP employs a technique called Multidimensional Analysis. Whereas a relational database stores all data in the form of rows and columns, a multidimensional dataset consists of axes and cells.MDX is a language for querying multidimensional databases, in the same way that SQL is used to query relational databases. It was originally defined as part of the OLE DB for OLAP specification, and a similar language, mdXML, is part of the XML for Analysis specification. It is the main query language implemented by Mondrian.MDX was introduced by Microsoft with Microsoft SQL Server OLAP Services in around 1998, as the language component of the OLE DB for OLAP API. More recently, MDX has appeared as part of the XML for Analysis API.A Mondrian OLAP System consists of four layers; working from the eyes of the end-user to the bowels of the data center, these are as follows: the presentation layer, the dimensional layer, the star layer, and the storage layer.The presentation layer determines what the end-user sees on his or her monitor, and how he or she can interact to ask new questions. There are many ways to present multidimensional datasets, including pivot tables, pie, line and bar charts, and advanced visualization tools such as clickable maps and dynamic graphics. These might be written in Swing or JSP, charts rendered in JPEG or GIF format, or transmitted to a remote application via XML. What all of these forms of presentation have in common is the multidimensional 'grammar' of dimensions, measures and...