Basic concepts of XSLFO

Here we review basic aspects of the XSLFO semantics and vocabulary, to gain a better understanding of how the technology works and how to use the specification itself.

Layout-based vs. content-based formatting

Two very different approaches to the formatting of information are contrasted. Layout-based formatting respects the constraints of the target medium, where limitations or capacities of the target may constrain the content or appearance of the information on a page. Content-based formatting respects the quantity and identity of the information, where as much of the target medium is generated to accommodate the information being formatted.

Formatting is different than rendering

The distinction between formatting and rendering is overviewed, comparing how to express what you want formatted vs. expressing how it is to be accomplished on the target device. This contrast is similar to the difference between declarative- and imperative- style programming methods, or the difference between XSLT's "transformation by example" paradigm vs. other algorithmic transformation approaches using programming languages.

Formatting model and vocabulary extends what is currently available for web presentation

The XSLFO semantics and vocabulary address different requirements than infinite-length web user agent windows to meet the needs of imposed arbitrary page boundaries on the presentation of information. These new semantics are inspired by the Document Style Semantics and Specification Language (DSSSL) International Standard ISO/IEC 10179, but in practice diverge from DSSSL towards Cascading Style Sheets 2 (CSS2) for compatibility with web-based processing.