IBM Cognos Report Design Best Practices

Installing the Appropriate Fonts on the Client Computer

The PDF extension does not embed the fonts in the report. In order to view a report in the correct font, you need to make sure that the fonts are not only installed on the Report Server, but also on the client computer that is used to view the report. Otherwise, font substitution will most likely occur.

HTML

The HTML rendering extension generates HTML 4.0 pages that are compatible with Microsoft® Internet Explorer, Mozilla Firefox, and Apple Safari.

There are several differences between HTML rendering and other renderings, including the following:

• The HTML rendering extension builds a table in HTML to contain each set of report items. Items are positioned in the table to preserve the report layout.
• Locations and sizes are expressed in millimeters (mm). Differences of less than .2 mm are rendered as 0 mm.
• HTML does not support item overlap. This can result in layout changes as the report is displayed.
• A subreport is rendered as a DIV tag in the HTML report.

Client Variations

When displayed on the client, an HTML report uses the browser-specific settings. In addition to possible font substitutions, other browser settings can likewise produce changes. If you want to precisely control the layout of the report on all clients used to view the report, consider using the image rendering extension.

Avoiding Blank Pages

Sometimes, you will see blank pages when you output reports to a physical page format such as PDF or print. Generally, this will happen when the size of the report body exceeds the size of the page.

To ensure that all the contents fit on a single page, the body width plus the margins should be less than the defined page width.

A textbox or other report item can cause the width of the body to exceed the page width, even when the portion of the item that exceeds the width has no visible contents. In addition, report items growing horizontally (matrix data regions and images set to automatically Autosize or Fit) can also cause the body to grow.

Using Page Breaks to Improve Performance for Large Reports

If you do not specify a page size or page breaks for a report that returns a large amount of data, some report formats will try to render the report as a single page.

For example, Excel has no default notion of a fixed page size. As a result, if you have a very large report, Excel will try to render it as a single worksheet. In general, using page breaks improves the performance for the users accessing the report, because they can view the first page while the rest of the report is being rendered.

Using Filters Instead of Query Parameters

Reporting Services has several methods for dynamically filtering report contents, including the following:

• Query parameters filter data at the source as it is retrieved.
• Report filters, applied to a dataset or data region, limit the data that is displayed from a generated report.

Using filters retrieves all data, but only data that is relevant to the user is displayed. This may be less efficient on an individual report basis than filtering at the source. However, it lets you retrieve the data once from the source and store in it a snapshot to serve many different user communities.

On the other hand, when using query parameters, you must revisit the data source for each new value of the query parameters. Filters enable you to use execution snapshots and still get full parameterization.

Adding Alternating Bars to a Table

It is possible for you to create a report that contains a table or matrix in which every other row is shaded. This bar effect makes it easier to visually track the different rows across a page.

To more closely simulate the old “green bar” paper that was used at one time to run large reports on high-volume data center printers, you can make the alternating bars green.

Following:

Adding Global Values to Headers and Footers

The members of the Global object collection, shown in Table 6, are available for use within report expressions.

Displaying Report Items in the Page Header

For long reports, you may want to include text from the body of the report in the header. For example, a directory listing could list the first and last occurrence of the last name field in the header to indicate the range of names included on the page.

Creating Drill-Down Links with Conditional Formatting

Reporting Services lets you put hidden items on a report page and make the items visible, based on the user interaction with the report.

You can use this capability to create a drill-down link within a report. For example, by clicking in a certain area, the user could drill down from a summary view of data to detailed information.

To do this, first select the group, column, or row of a table to hide and set its Hidden element to True. Next, create a toggle item for a text box in a containing group. Then, when a user clicks the text box, hidden data becomes visible or visible data disappears.