About Arbortext Styler > Document Preview and Publishing > Print Engine Comparison
Print Engine Comparison
Arbortext Styler permits the use of three different print engines, i.e. three different technologies for formatting documents for print or PDF - PTC Arbortext Layout Developer (PTC ALD), FOSI, and XSL-FO. You may select one of these as the default engine for your Arbortext Styler stylesheet and choose to use any of them when previewing print or PDF output from the Arbortext Styler UI. Each has its own advantages, depending on the type of content or document you are publishing,
The FOSI and XSL-FO print engines are on sustained support and do not receive enhancements or maintenance fixes. PTC ALD is the recommended engine for print/PDF output.
Refer to Logic for Print/Preview Engine Selection for information on how settings in your PTC Arbortext environment determine the effective print engine it will use as a default.
Most applications should use the PTC ALD engine. This engine supports more features than the others and is where PTC Arbortext plans to devote the most resources going forward. The next sections provide a summary of each print engine, their benefits, and the features they support.
PTC ALD Engine
Summary: Users who need support for Hebrew, Arabic, Thai, Chinese, Japanese, or Korean languages, or who need more flexibility in their page layout are strongly encouraged to use the PTC ALD engine. PTC Arbortext encourages the use of the PTC ALD engine unless there is an important reason to use one of the other engines.
Features currently supported only by this engine include:
1. Right to left formatting (for example, for Hebrew and Arabic language content)
2. Hanging punctuation (for example, for East Asian language content)
3. Pinyin indexing for Simplified Chinese without the need to manually enter Pinyin sort keys
4. Stroke number indexing for Traditional Chinese
5. Borders for page regions
6. Region avoidance (special handling for overlapping page regions)
7. Rotation of main content flow permitted to any angle
8. Pages containing main content flow permitted to have different widths
9. Columns on a page permitted to vary in width
10. Gutter rules between columns
11. Left blank pages permitted to vary from right blank pages
12. Automatic shrinking of graphics to avoid oversets
13. Output of tagged PDF
14. Best support for side by side formatting
15. Stylesheet extensions use JavaScript and PTC Arbortext Layout Developer’s own Formatting Object Model
FOSI Engine
Summary: The FOSI engine might be the engine of choice for those who:
do not need any of the features supported only by PTC ALD, do not plan to format content in Hebrew, Arabic, Thai , Chinese, Japanese, or Korean languages, and either:
have stylesheet authors with FOSI expertise and need to extend their stylesheets with edited source, or
require the fastest possible performance
already have existing stylesheets with extensive edited FOSI source, or mature stylesheets that will not require significant modification
Features currently supported only by this engine include:
Run-in titles
Stylesheet extensions involve editing FOSI source
XSL-FO Engine
Summary: The XSL-FO engine might be the engine of choice for companies whose most important criterion when publishing is the use of standards.
Features currently supported only by this engine include:
Stylesheet extensions involve editing the FO-generating XSLT source
In version 6.1 the FOSI engine is somewhat faster than PTC ALD, though we expect to close that gap over time.  XSL-FO is significantly slower, and that is unlikely to change.