IBM Cognos Report Design Best Practices

Using Tables Instead of Lists for Excel-specific Reports

A table uses a fixed column width. This matches very well with the tabular format of Excel reports. The items in the report table will line up as you expect them to when rendered in Excel.

In contrast, a list is a freeform style. Items in the list are positioned in the worksheet relative to their location in the report. This can lead to unexpected results. If your report uses a list, be sure to check the rendering to Excel to see if the results are acceptable.

Even with tables, if you have a header that spans multiple columns in a report, the Excel rendering extension may need to merge cells or introduce new columns. This can affect the ability to sort and manipulate data in the Excel spreadsheet. If you are planning to render to Excel, try to ensure that the left or right edges of the report item line up in order to minimize cell merging.

Maximum Number of Pages in Long Reports

To prevent Excel from generating an error, you should keep track of the number of pages in lengthy reports. Specifically, each page in a report becomes a worksheet in Excel. However, Excel can only support a maximum number of worksheets per workbook, limited by available memory. If the report pages exceed that limit, Excel generates an error.

Color Differences in Rendering to Excel

Excel supports a predefined set of colors. When you render a report, the Excel rendering extension maps the report colors to the best match in the natively supported colors in Excel.

Image

The Image rendering extension renders reports in bitmap or metafiles. By default, it renders data in TIFF format. However, it can generate files in any format supported by GDI+, including BMP, EMF, GIF, JPEG, and PNG.

An image rendering extension on the Report Server processes the report on a virtual page and creates the image from that virtual page. As a result, the image-based report will look the same, in terms of font and layout, on every client.

When you are working with TIFF files, they can be viewed in multiple pages. However, other image formats generate one file for each report page.

Image rendering also supports page height, page width, and margins. Any headers and footers contained in the report are rendered inside the margins of the report.

Using Image Rendering to Create the Same Reports on All Clients

If you want your reports to look the same on every client, you should use image rendering. Specifically, HTML reports use the client font and browser settings when rendering reports. This means that the layout can change when different browser clients are used. Because image files are formatted on the Report Server, they are rendered to an image file that should appear the same on every client.

Installing the Appropriate Fonts on the Report Server

You should make sure that the fonts you need are installed on the Report Server. This is because the report is actually rendered on the Report Server and it uses the fonts that are installed on the Report Server.

Portable Document Format

The portable document format (PDF) rendering extension creates reports that can be viewed with Adobe Acrobat readers. The PDF extension is similar to the image extension in many ways, except for the following important differences:

• Fonts are not embedded in the PDF reports.
• Document maps are rendered as PDF bookmarks.
• You can specify page width and height, margins, and resolution of the PDF, among other device options.
• The rendering extension creates PDF 1.3 files that are compatible with Adobe Acrobat 4.0 and later versions.
• The PDF rendering extension does not support RepeatWith.