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Re: RFC: goals for rewritten output subsystem

From: John Darrington
Subject: Re: RFC: goals for rewritten output subsystem
Date: Fri, 30 May 2008 16:49:17 +0800
User-agent: Mutt/1.5.17+20080114 (2008-01-14)

I think this is a good summary of what we need.  The only things I
would add are:

* I would make item 4 a secondary goal.  Anyone who runs a procedure
  which creates a table larger than the memory of any modernish
  machine has probably made a mistake.

* Regarding internationalisation, I would like to see it possible for
  the output to be translated to a different locale to that of the
  user interface.

* Another goal, which isn't explicitly mentioned below:  It should be
  straightforward for us or 3rd parties to write the necessary code 
  to have output in a new format eg dvi, TeX, pdf ODF or something
  which has yet to be invented.


On Thu, May 29, 2008 at 10:31:59PM -0700, Ben Pfaff wrote:
     Hi everyone.
     One of my goals for the version of PSPP following the 0.6.0
     release is to improve the output subsystem.  I have some ideas
     for how to do this, that I want to discuss with the list, but I
     thought that the first step should be to talk about why the
     existing output subsystem is inadequate and how we'd like its
     successor to be an improvement.
     I've discussed a little of this briefly with Jason over IRC.
     Some of the goals relate to what I'd call genuine problems with
     the PSPP output subsystem:
     1. Problem: As a developer, it is difficult to work with the
        output subsystem.  Formatting output for a procedure requires
        writing more code than it should.  Code for output requires
        careful thought about how the formatted output should look.
        It also tightly binds cosmetic details of output to the code
        that produces it.
        Goal: The new output subsystem should allow developers to
        focus on data output, not formatting.  Ideally, data output
        should be completely separated from presentation details.
     2. Problem: PSPP output is not easily machine-readable in a
        semantically meaningful way.  That is, data produced as part
        of the output is difficult to extract for use by other
        software or by subsequent PSPP procedures.  Another aspect of
        the same issue is that PSPP tests that compare output end up
        compare cosmetic details of the formatting, not just the data
        Goal: The new output subsystem should be able to produce
        machine-readable, semantically meaningful data output in at
        least one widely understood format, such as CSV or an XML
        schema.  Then tests can compare this output format.
     3. Problem: Output is fixed in form at the time of its
        generation; that is, there is no practical way for the GUI to
        allow the user to re-style or reformat tables, and certainly
        not to do anything more advanced like the "pivot table"
        features of spreadsheets.
        Goal: Provide good interactive output support.
     4. Problem: Tables larger than memory cannot be efficiently
        formatted.  (This is why the LIST procedure more or less
        sidesteps the output subsystem, without producing real tables
        in its output.)
        Goal: Efficiently support tables larger than memory.
     5. Problem: As a user, the output subsystem is difficult to
        Goal: Simplify configuration.
     Other goals are really just improvements:
     6. Support the OMS (output management system) commands from the
        competing software, to the extent possible.
     Finally, a few properties that I'd like to retain:
     7. Keep performance reasonable.
     8. Retain potential for internationalization of output.  (Right
        now it's just "potential" only because no one has actually
        translated it.)
     9. Make sure that reasonably formatted plain text output with
        tables and (in separate files) graphs is still possible.  It's
        still sometimes easier to view a text file than a PDF or HTML
     I've been doing experiments off and on over the last few years,
     trying to figure out a good way to do it.  Now I think I may have
     a reasonable approach.  But I'd like to agree on what our goals
     are before I go on.  So does anyone have anything to add or
     detract to the above?  This will be about third or fourth
     iteration of the PSPP output subsystem.  Perhaps we can get it
     right this time...
     Ben Pfaff
     pspp-dev mailing list

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