About data sources

Data sets present in information objects and data objects classify data fields retrieved from a data source, in dimensions, measures, and attributes. These categories are specified by the information object developer, or the data object developer at the time of designing the information object or data object, and cannot be modified using BIRT Studio. It is useful to understand these categories to use them appropriately in a report design.

Dimensions are data fields that group other data fields. Each dimension field can contain multiple attributes. Attributes are typically associated with a dimension. Table 1-1 lists the possible attributes for each dimension field.

Table 1-1

Dimensions with associated attribute fields

Dimension	Attribute fields
Product Line	Product name, product code
Region	Country, state, city

Measures are data fields that can be aggregated, or computed such as revenue, profit, price, and so on.

Data sets included in templates, information objects, and data objects provide easy access to the data fields that contain the data for a report. For example, an information object or a data set named CustomerData can contain customer information fields, such as customer name, address, phone number, and so on. You choose this data source to create a report that lists customers and their contact information.

You use an information object to create a report table, a summary table or a chart. You use a data object to create a report table, a chart, or a summary table. If the data object contains one or more cubes, you can use it to create a cross tab. BIRT Studio provides a convenient Table Builder wizard that enables you select data fields from information objects or data objects and insert them into a report design.

A data object is a collection of data sets and cubes that can be used to create BIRT reports. A data object contains data sets and cube items, specified by the data object developer. A data object must contain at least one data set but does not need to contain a cube.

A data object provides access to predesigned data sources, data sets, and sometimes cubes. You use Actuate BIRT Designer Professional to create data objects. Report developers create data objects to streamline the report creation process. Data objects provide the following benefits:

Simplified data access and retrieval. The predesigned data sources, data sets, and cubes in a data object enable report developers to select the data to use in a report without requiring knowledge about the underlying data source, how to connect to it, and how to extract data from it.

Reusability across multiple reports. If a suite of reports require the same data, designing the data sources, data sets, and cubes once in a shared data object eliminates the need to design the same elements repeatedly for each report.

Dynamic updates to data items. Changes to data items in a data object propagate to reports that use the data object.

A report accesses data from a data object using either a data object design (.datadesign) file or a data object store (.data) file. The data design file retrieves data, on demand, each time the report is run. A data object store contains cached, or materialized, data, and provides more efficient access to data. If getting real-time data is more important than report generation speed, use the data object design file. If data in the underlying data source does not change constantly, or if a data object store is generated regularly, use the data object store.

You can limit the data available to a report design by applying filters to a data set in a template, an information object, or a data object. Both information objects and data objects often contain very large amounts of data. Using filters to limit the data available to a report design is useful when you need to create a report that displays specific data quickly. For example, if the data set displays sales totals for the years 2003, 2004, and 2005, and you need to view the sales totals for the most recent of those years, you can specify a filter condition such that BIRT Studio retrieves and displays data only for the year 2005 in the report design.

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