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  • XSL has "interpretive overhead" that FOSI does not have. FOSI  
    is compiled, but XSL is interpreted at run-time. According to

    A program translated by a compiler is often much faster than an
    interpreter executing the same program: even a 10:1 ratio is not
    uncommon. Interpreting code is slower than running the compiled code
    because the interpreter must analyse each statement in the program
    each time it is executed and then perform the desired action whereas
    the compiled code just performs the action. This run-time analysis is
    known as "interpretive overhead."

  • XSL-FO has a required transformation phase (XSLT)  FOSI does
    not have. With FOSI, only exception cases are "transformed."
    The FOSI standard states:

    The general composition model of almost all document processing
    systems is sequential: the document is processed from front to back
    (in document order) and the input content is composed onto the output
    pages so that the information is presented basically in the same order
    in which it was input.

  • XSLT is inherently slow because it is a functional programming
    language. According to Wikipedia:

    Functional languages have long been criticised as resource-hungry,
    both in terms of CPU resources and memory. . . . implementations
    of functional languages have begun to emphasize speed as well as

  • As a functional language, XSLT describes the solution to the
    problem, which means each XSL-FO stylesheet developer is
    responsible for describing the optimum solution for best

    FOSI, on the other hand, is a declarative language, which describes
    the problem and leaves the solution to the interpreting software. The
    interpreting software is also responsible for optimizing performance.

  • XSL is inefficient because it must traverse the document many
    times during the formatting process.

    FOSI is designed to minimize document traversal in order to maximize
    formatting speed.

  • XSL-FO must rely on tables for side-by-side formatting.

    Tables take longer to format with Arbortext than flowing text.

  • Arbortext's formatting process maps XSL-FO to FOSI.

    Mapping XSL-FO to FOSI means XSL-FO will always take longer than
FOSI is significantly faster than XSL-FO, as discussed below.
Expert FOSI Consulting for Arbortext
World expert on applied FOSI
Expert FOSI Consulting             941-312-7636         2015
FOSI formatting
always runs at
top speed
FOSI has a feature
that can make forrmating
2 to 4 times faster