Provided by: po4a_0.45-1_all 
NAME
po4a - framework to translate documentation and other materials
Introduction
The po4a (PO for anything) project goal is to ease translations (and more interestingly,
the maintenance of translations) using gettext tools on areas where they were not expected
like documentation.
Table of content
This document is organized as follow:
1 Why should I use po4a? What is it good for?
This introducing chapter explains the motivation of the project and its philosophy.
You should read it first if you are in the process of evaluating po4a for your own
translations.
2 How to use po4a?
This chapter is a sort of reference manual, trying to answer the users' questions and
to give you a better understanding of the whole process. This introduces how to do
things with po4a and serve as an introduction to the documentation of the specific
tools.
HOWTO begin a new translation?
HOWTO change the translation back to a documentation file?
HOWTO update a po4a translation?
HOWTO convert a pre-existing translation to po4a?
HOWTO add extra text to translations (like translator's name)?
HOWTO do all this in one program invocation?
HOWTO customize po4a?
3 How does it work?
This chapter gives you a brief overview of the po4a internals, so that you may feel
more confident to help us maintaining and improving it. It may also help you
understanding why it does not do what you expected, and how to solve your problems.
4 FAQ
This chapter groups the Frequently Asked Questions. In fact, most of the questions for
now could be formulated that way: "Why is it designed this way, and not that one?" If
you think po4a isn't the right answer to documentation translation, you should
consider reading this section. If it does not answer your question, please contact us
on the <po4a-devel@lists.alioth.debian.org> mailing list. We love feedback.
5 Specific notes about modules
This chapter presents the specificities of each module from the translator and
original author's point of view. Read this to learn the syntax you will encounter when
translating stuff in this module, or the rules you should follow in your original
document to make translators' life easier.
Actually, this section is not really part of this document. Instead, it is placed in
each module's documentation. This helps ensuring that the information is up to date by
keeping the documentation and the code together.
Why should I use po4a? What it is good for?
I like the idea of open-source software, making it possible for everybody to access
software and its source code. But being French, I'm well aware that the licensing is not
the only restriction to the openness of software: non-translated free software is useless
for non-English speakers, and we still have some work to make it available to really
everybody out there.
The perception of this situation by the open-source actors did dramatically improve
recently. We, as translators, won the first battle and convinced everybody of the
translations' importance. But unfortunately, it was the easy part. Now, we have to do the
job and actually translate all this stuff.
Actually, open-source software themselves benefit of a rather decent level of translation,
thanks to the wonderful gettext tool suite. It is able to extract the strings to translate
from the program, present a uniform format to translators, and then use the result of
their works at run time to display translated messages to the user.
But the situation is rather different when it comes to documentation. Too often, the
translated documentation is not visible enough (not distributed as a part of the program),
only partial, or not up to date. This last situation is by far the worst possible one.
Outdated translation can reveal worse than no translation at all to the users by
describing old program behavior which are not in use anymore.
The problem to solve
Translating documentation is not very difficult in itself. Texts are far longer than the
messages of the program and thus take longer to be achieved, but no technical skill is
really needed to do so. The difficult part comes when you have to maintain your work.
Detecting which parts did change and need to be updated is very difficult, error-prone and
highly unpleasant. I guess that this explains why so much translated documentation out
there are outdated.
The po4a answers
So, the whole point of po4a is to make the documentation translation maintainable. The
idea is to reuse the gettext methodology to this new field. Like in gettext, texts are
extracted from their original locations in order to be presented in a uniform format to
the translators. The classical gettext tools help them updating their works when a new
release of the original comes out. But to the difference of the classical gettext model,
the translations are then re-injected in the structure of the original document so that
they can be processed and distributed just like the English version.
Thanks to this, discovering which parts of the document were changed and need an update
becomes very easy. Another good point is that the tools will make almost all the work when
the structure of the original document gets fundamentally reorganized and when some
chapters are moved around, merged or split. By extracting the text to translate from the
document structure, it also keeps you away from the text formatting complexity and reduces
your chances to get a broken document (even if it does not completely prevent you to do
so).
Please also see the FAQ below in this document for a more complete list of the advantages
and disadvantages of this approach.
Supported formats
Currently, this approach has been successfully implemented to several kinds of text
formatting formats:
man
The good old manual pages' format, used by so much programs out there. The po4a support is
very welcome here since this format is somewhat difficult to use and not really friendly
to the newbies. The Locale::Po4a::Man(3pm) module also supports the mdoc format, used by
the BSD man pages (they are also quite common on Linux).
pod
This is the Perl Online Documentation format. The language and extensions themselves are
documented that way, as well as most of the existing Perl scripts. It makes easy to keep
the documentation close to the actual code by embedding them both in the same file. It
makes programmer life easier, but unfortunately, not the translator one.
sgml
Even if somewhat superseded by XML nowadays, this format is still used rather often for
documents which are more than a few screens long. It allows you to make complete books.
Updating the translation of so long documents can reveal to be a real nightmare. diff
reveals often useless when the original text was re-indented after update. Fortunately,
po4a can help you in that process.
Currently, only the DebianDoc and DocBook DTD are supported, but adding support to a new
one is really easy. It is even possible to use po4a on an unknown SGML DTD without
changing the code by providing the needed information on the command line. See
Locale::Po4a::Sgml(3pm) for details.
TeX / LaTeX
The LaTeX format is a major documentation format used in the Free Software world and for
publications. The Locale::Po4a::LaTeX(3pm) module was tested with the Python
documentation, a book and some presentations.
texinfo
All the GNU documentation is written in this format (that's even one of the requirement to
become an official GNU project). The support for Locale::Po4a::Texinfo(3pm) in po4a is
still at the beginning. Please report bugs and feature requests.
xml
The XML format is a base format for many documentation formats.
Currently, the DocBook DTD is supported by po4a. See Locale::Po4a::Docbook(3pm) for
details.
others
Po4a can also handle some more rare or specialized formats, such as the documentation of
compilation options for the 2.4.x kernels or the diagrams produced by the dia tool. Adding
a new one is often very easy and the main task is to come up with a parser of your target
format. See Locale::Po4a::TransTractor(3pm) for more information about this.
Unsupported formats
Unfortunately, po4a still lacks support for several documentation formats.
There is a whole bunch of other formats we would like to support in po4a, and not only
documentation ones. Indeed, we aim at plugging all "market holes" left by the classical
gettext tools. It encompass package descriptions (deb and rpm), package installation
scripts questions, package changelogs, and all specialized file formats used by the
programs such as game scenarios or wine resource files.
How to use po4a?
This chapter is a sort of reference manual, trying to answer the users' questions and to
give you a better understanding of the whole process. This introduces how to do things
with po4a and serve as an introduction to the documentation of the specific tools.
Graphical overview
The following schema gives an overview of the process of translating documentation using
po4a. Do not be afraid by its apparent complexity, it comes from the fact that the whole
process is represented here. Once you converted your project to po4a, only the right part
of the graphic is relevant.
Note that master.doc is taken as an example for the documentation to be translated and
translation.doc is the corresponding translated text. The suffix could be .pod, .xml, or
.sgml depending on its format. Each part of the picture will be detailed in the next
sections.
master.doc
|
V
+<-----<----+<-----<-----<--------+------->-------->-------+
: | | :
{translation} | { update of master.doc } :
: | | :
XX.doc | V V
(optional) | master.doc ->-------->------>+
: | (new) |
V V | |
[po4a-gettextize] doc.XX.po--->+ | |
| (old) | | |
| ^ V V |
| | [po4a-updatepo] |
V | | V
translation.pot ^ V |
| | doc.XX.po |
| | (fuzzy) |
{ translation } | | |
| ^ V V
| | {manual editing} |
| | | |
V | V V
doc.XX.po --->---->+<---<---- doc.XX.po addendum master.doc
(initial) (up-to-date) (optional) (up-to-date)
: | | |
: V | |
+----->----->----->------> + | |
| | |
V V V
+------>-----+------<------+
|
V
[po4a-translate]
|
V
XX.doc
(up-to-date)
On the left part, the conversion of a translation not using po4a to this system is shown.
On the top of the right part, the action of the original author is depicted (updating the
documentation). The middle of the right part is where the automatic actions of po4a are
depicted. The new material are extracted, and compared against the exiting translation.
Parts which didn't change are found, and previous translation is used. Parts which where
partially modified are also connected to the previous translation, but with a specific
marker indicating that the translation must be updated. The bottom of the figure shows how
a formatted document is built.
Actually, as a translator, the only manual operation you have to do is the part marked
{manual editing}. Yeah, I'm sorry, but po4a helps you translate. It does not translate
anything for you...
HOWTO begin a new translation?
This section presents the needed steps required to begin a new translation with po4a. The
refinements involved in converting an existing project to this system are detailed in the
relevant section.
To begin a new translation using po4a, you have to do the following steps:
- Extract the text which have to be translated from the original <master.doc> document
into a new translation template <translation.pot> file (the gettext format). For that,
use the po4a-gettextize program this way:
$ po4a-gettextize -f <format> -m <master.doc> -p <translation.pot>
<format> is naturally the format used in the master.doc document. As expected, the
output goes into translation.pot. Please refer to po4a-gettextize(1) for more details
about the existing options.
- Actually translate what should be translated. For that, you have to rename the POT file
for example to doc.XX.po (where XX is the ISO639 code of the language you are
translating to, e.g. fr for French), and edit the resulting file. It is often a good
idea to not name the file XX.po to avoid confusion with the translation of the program
messages, but this your call. Don't forget to update the PO file headers, they are
important.
The actual translation can be done using the Emacs' or Vi's PO mode, Lokalize (KDE
based), Gtranslator (GNOME based) or whichever program you prefer to use for them (e.g.
Virtaal).
If you wish to learn more about this, you definitively need to refer to the gettext
documentation, available in the gettext-doc package.
HOWTO change the translation back to a documentation file?
Once you're done with the translation, you want to get the translated documentation and
distribute it to users along with the original one. For that, use the po4a-translate(1)
program like that (where XX is the language code):
$ po4a-translate -f <format> -m <master.doc> -p <doc.XX.po> -l <XX.doc>
As before, <format> is the format used in the master.doc document. But this time, the PO
file provided with the -p flag is part of the input. This is your translation. The output
goes into XX.doc.
Please refer to po4a-translate(1) for more details.
HOWTO update a po4a translation?
To update your translation when the original master.doc file has changed, use the
po4a-updatepo(1) program like that:
$ po4a-updatepo -f <format> -m <new_master.doc> -p <old_doc.XX.po>
(Please refer to po4a-updatepo(1) for more details)
Naturally, the new paragraph in the document won't get magically translated in the PO file
with this operation, and you'll need to update the PO file manually. Likewise, you may
have to rework the translation for paragraphs which were modified a bit. To make sure you
won't miss any of them, they are marked as "fuzzy" during the process and you have to
remove this marker before the translation can be used by po4a-translate. As for the
initial translation, the best is to use your favorite PO editor here.
Once your PO file is up-to-date again, without any untranslated or fuzzy string left, you
can generate a translated documentation file, as explained in the previous section.
HOWTO convert a pre-existing translation to po4a?
Often, you used to translate manually the document happily until a major reorganization of
the original master.doc document happened. Then, after some unpleasant tries with diff or
similar tools, you want to convert to po4a. But of course, you don't want to loose your
existing translation in the process. Don't worry, this case is also handled by po4a tools
and is called gettextization.
The key here is to have the same structure in the translated document and in the original
one so that the tools can match the content accordingly.
If you are lucky (i.e., if the structures of both documents perfectly match), it will work
seamlessly and you will be set in a few seconds. Otherwise, you may understand why this
process has such an ugly name, and you'd better be prepared to some grunt work here. In
any case, remember that it is the price to pay to get the comfort of po4a afterward. And
the good point is that you have to do so only once.
I cannot emphasis this too much. In order to ease the process, it is thus important that
you find the exact version which were used to do the translation. The best situation is
when you noted down the VCS revision used for the translation and you didn't modify it in
the translation process, so that you can use it.
It won't work well when you use the updated original text with the old translation. It
remains possible, but is harder and really should be avoided if possible. In fact, I guess
that if you fail to find the original text again, the best solution is to find someone to
do the gettextization for you (but, please, not me ;).
Maybe I'm too dramatic here. Even when things go wrong, it remains ways faster than
translating everything again. I was able to gettextize the existing French translation of
the Perl documentation in one day, even though things did went wrong. That was more than
two megabytes of text, and a new translation would have lasted months or more.
Let me explain the basis of the procedure first and I will come back on hints to achieve
it when the process goes wrong. To ease comprehension, let's use above example once again.
Once you have the old master.doc again which matches with the translation XX.doc, the
gettextization can be done directly to the PO file doc.XX.po without manual translation of
translation.pot file:
$ po4a-gettextize -f <format> -m <old_master.doc> -l <XX.doc> -p <doc.XX.po>
When you're lucky, that's it. You converted your old translation to po4a and can begin
with the updating task right away. Just follow the procedure explained a few section ago
to synchronize your PO file with the newest original document, and update the translation
accordingly.
Please note that even when things seem to work properly, there is still room for errors in
this process. The point is that po4a is unable to understand the text to make sure that
the translation match the original. That's why all strings are marked as "fuzzy" in the
process. You should check each of them carefully before removing those markers.
Often the document structures don't match exactly, preventing po4a-gettextize from doing
its job properly. At that point, the whole game is about editing the files to get their
damn structures matching.
It may help to read the section Gettextization: how does it work? below. Understanding
the internal process will help you to make this work. The good point is that
po4a-gettextize is rather verbose about what went wrong when it happens. First, it
pinpoints where in the documents the structures' discrepancies are. You will learn the
strings that don't match, their positions in the text, and the type of each of them.
Moreover, the PO file generated so far will be dumped to gettextization.failed.po.
- Remove all extra parts of the translations, such as the section in which you give the
translator name and thank every people who contributed to the translation. Addenda,
which are described in the next section, will allow you to re-add them afterward.
- Do not hesitate to edit both the original and the translation. The most important
thing is to get the PO file. You will be able to update it afterward. That being said,
editing the translation should be preferred when both are possible since it makes
things easier when the gettextization is done.
- If needed, kill some parts of the original if they happen to not be translated. When
synchronizing the PO with the document afterward, they will come back from themselves.
- If you changed the structure a bit (to merge two paragraphs, or split another one),
undo those changes. If there are issues in the original, you should inform the
original author. Fixing them in your translation only fixes them for a part of the
community. And moreover, it's impossible when using po4a ;)
- Sometimes, the paragraph content does match, but their types don't. Fixing it is
rather format-dependant. In POD and man, it often comes from the fact that one of the
two contains a line beginning with a white space where the other doesn't. In those
formats, such paragraph cannot be wrapped and thus become a different type. Just
remove the space and you are fine. It may also be a typo in the tag name.
Likewise, two paragraphs may get merged together in POD when the separating line
contains some spaces, or when there is no empty line before the =item line and the
content of the item.
- Sometimes, there is a desynchronization between the files, and the translation is
attached to the wrong original paragraph. It is the sign that the real problem was
before in the files. Check gettextization.failed.po to see when the desynchronization
begins, and fix it there.
- Sometimes, you get the strong feeling that po4a ate some parts of the text, either the
original or the translation. gettextization.failed.po indicates that both of them
where gently matching, and then the gettextization fails because it tried to match one
paragraph with the one after (or before) the right one, as if the right one
disappeared. Curse po4a as I did when it first happened to me. Generously.
This unfortunate situation happens when the same paragraph is repeated over the
document. In that case, no new entry is created in the PO file, but a new reference is
added to the existing one instead.
So, when the same paragraph appears twice in the original but both are not translated
in the exact same way each time, you will get the feeling that a paragraph of the
original disappeared. Just kill the new translation. If you prefer to kill the first
translation instead when it was actually better, remove the second one from where it
is and put it in place of the first one.
In the contrary, if two similar but different paragraphs were translated in the exact
same way, you will get the feeling that a paragraph of the translation disappeared. A
solution is to add a stupid string to the original paragraph (such as "I'm
different"). Don't be afraid, those things will disappear during the synchronization,
and when the added text is short enough, gettext will match your translation to the
existing text (marking it as fuzzy, but you don't really care since all strings are
fuzzy after gettextization).
Hopefully, those tips will help you making your gettextization work and obtain your
precious PO file. You are now ready to synchronize your file and begin your translation.
Please note that on large text, it may happen that the first synchronization takes a long
time.
For example, the first po4a-updatepo of the Perl documentation's French translation (5.5
Mb PO file) took about two days full on a 1Ghz G5 computer. Yes, 48 hours. But the
subsequent ones only take a dozen of seconds on my old laptop. This is because the first
time, most of the msgid of the PO file don't match any of the POT file ones. This forces
gettext to search for the closest one using a costly string proximity algorithm.
HOWTO add extra text to translations (like translator's name)?
Because of the gettext approach, doing this becomes more difficult in po4a than it was
when simply editing a new file along the original one. But it remains possible, thanks to
the so-called addenda.
It may help the comprehension to consider addenda as a sort of patches applied to the
localized document after processing. They are rather different from the usual patches
(they have only one line of context, which can embed Perl regular expression, and they can
only add new text without removing any), but the functionalities are the same.
Their goal is to allow the translator to add extra content to the document which is not
translated from the original document. The most common usage is to add a section about the
translation itself, listing contributors and explaining how to report bug against the
translation.
An addendum must be provided as a separate file. The first line constitutes a header
indicating where in the produced document they should be placed. The rest of the addendum
file will be added verbatim at the determined position of the resulting document.
The header has a pretty rigid syntax: It must begin with the string PO4A-HEADER:, followed
by a semi-colon (;) separated list of key=value fields. White spaces ARE important. Note
that you cannot use the semi-colon char (;) in the value, and that quoting it doesn't
help.
Again, it sounds scary, but the examples given below should help you to find how to write
the header line you need. To illustrate the discussion, assume we want to add a section
called "About this translation" after the "About this document" one.
Here are the possible header keys:
position (mandatory)
a regexp. The addendum will be placed near the line matching this regexp. Note that
we're speaking about the translated document here, not the original. If more than a
line match this expression (or none), the addition will fail. It is indeed better to
report an error than inserting the addendum at the wrong location.
This line is called position point in the following. The point where the addendum is
added is called insertion point. Those two points are near one from another, but not
equal. For example, if you want to insert a new section, it is easier to put the
position point on the title of the preceding section and explain po4a where the
section ends (remember that position point is given by a regexp which should match a
unique line).
The localization of the insertion point with regard to the position point is
controlled by the mode, beginboundary and endboundary fields, as explained below.
In our case, we would have:
position=<title>About this document</title>
mode (mandatory)
It can be either the string before or after, specifying the position of the addendum,
relative to the position point.
Since we want the new section to be placed below the one we are matching, we have:
mode=after
beginboundary (used only when mode=after, and mandatory in that case)
endboundary (idem)
regexp matching the end of the section after which the addendum goes.
When mode=after, the insertion point is after the position point, but not directly
after! It is placed at the end of the section beginning at the position point, i.e.,
after or before the line matched by the ???boundary argument, depending on whether you
used beginboundary or endboundary.
In our case, we can choose to indicate the end of the section we match by adding:
endboundary=</section>
or to indicate the beginning of the next section by indicating:
beginboundary=<section>
In both case, our addendum will be placed after the </section> and before the
<section>. The first one is better since it will work even if the document gets
reorganized.
Both forms exist because documentation formats are different. In some of them, there
is a way to mark the end of a section (just like the </section> we just used), while
some other don't explicitly mark the end of section (like in man). In the former case,
you want to make a boundary matching the end of a section, so that the insertion point
comes after it. In the latter case, you want to make a boundary matching the beginning
of the next section, so that the insertion point comes just before it.
This can seem obscure, but hopefully, the next examples will enlighten you.
To sum up the example we used so far, in order to add a section called "About this
translation" after the "About this document" one in a SGML document, you can use either of
those header lines:
PO4A-HEADER: mode=after; position=About this document; endboundary=</section>
PO4A-HEADER: mode=after; position=About this document; beginboundary=<section>
If you want to add something after the following nroff section:
.SH "AUTHORS"
you should put a position matching this line, and a beginboundary matching the beginning
of the next section (i.e., ^\.SH). The addendum will then be added after the position
point and immediately before the first line matching the beginboundary. That is to say:
PO4A-HEADER:mode=after;position=AUTHORS;beginboundary=\.SH
If you want to add something into a section (like after "Copyright Big Dude") instead of
adding a whole section, give a position matching this line, and give a beginboundary
matching any line.
PO4A-HEADER:mode=after;position=Copyright Big Dude, 2004;beginboundary=^
If you want to add something at the end of the document, give a position matching any line
of your document (but only one line. Po4a won't proceed if it's not unique), and give an
endboundary matching nothing. Don't use simple strings here like "EOF", but prefer those
which have less chance to be in your document.
PO4A-HEADER:mode=after;position=<title>About</title>;beginboundary=FakePo4aBoundary
In any case, remember that these are regexp. For example, if you want to match the end of
a nroff section ending with the line
.fi
don't use .fi as endboundary, because it will match with "the[ fi]le", which is obviously
not what you expect. The correct endboundary in that case is: ^\.fi$.
If the addendum doesn't go where you expected, try to pass the -vv argument to the tools,
so that they explain you what they do while placing the addendum.
More detailed example
Original document (POD formatted):
|=head1 NAME
|
|dummy - a dummy program
|
|=head1 AUTHOR
|
|me
Then, the following addendum will ensure that a section (in French) about the translator
is added at the end of the file. (in French, "TRADUCTEUR" means "TRANSLATOR", and "moi"
means "me")
|PO4A-HEADER:mode=after;position=AUTEUR;beginboundary=^=head
|
|=head1 TRADUCTEUR
|
|moi
In order to put your addendum before the AUTHOR, use the following header:
PO4A-HEADER:mode=after;position=NOM;beginboundary=^=head1
This works because the next line matching the beginboundary /^=head1/ after the section
"NAME" (translated to "NOM" in French), is the one declaring the authors. So, the addendum
will be put between both sections.
HOWTO do all this in one program invocation?
The use of po4a proved to be a bit error prone for the users since you have to call two
different programs in the right order (po4a-updatepo and then po4a-translate), each of
them needing more than 3 arguments. Moreover, it was difficult with this system to use
only one PO file for all your documents when more than one format was used.
The po4a(1) program was designed to solve those difficulties. Once your project is
converted to the system, you write a simple configuration file explaining where your
translation files are (PO and POT), where the original documents are, their formats and
where their translations should be placed.
Then, calling po4a(1) on this file ensures that the PO files are synchronized against the
original document, and that the translated document are generated properly. Of course, you
will want to call this program twice: once before editing the PO file to update them and
once afterward to get a completely updated translated document. But you only need to
remember one command line.
HOWTO customize po4a?
po4a modules have options (specified with the -o option) that can be used to change the
module behavior.
It is also possible to customize a module or new / derivative / modified modules by
putting a module in lib/Locale/Po4a/, and adding lib to the paths specified by the PERLLIB
or PERL5LIB environment. For example:
PERLLIB=$PWD/lib po4a --previous po4a/po4a.cfg
Note: the actual name of the lib directory is not important.
How does it work?
This chapter gives you a brief overview of the po4a internals, so that you may feel more
confident to help us maintaining and improving it. It may also help you understanding why
it does not do what you expected, and how to solve your problems.
What's the big picture here?
The po4a architecture is object oriented (in Perl. Isn't that neat?). The common ancestor
to all parser classes is called TransTractor. This strange name comes from the fact that
it is at the same time in charge of translating document and extracting strings.
More formally, it takes a document to translate plus a PO file containing the translations
to use as input while producing two separate outputs: Another PO file (resulting of the
extraction of translatable strings from the input document), and a translated document
(with the same structure than the input one, but with all translatable strings replaced
with content of the input PO). Here is a graphical representation of this:
Input document --\ /---> Output document
\ TransTractor:: / (translated)
+-->-- parse() --------+
/ \
Input PO --------/ \---> Output PO
(extracted)
This little bone is the core of all the po4a architecture. If you omit the input PO and
the output document, you get po4a-gettextize. If you provide both input and disregard the
output PO, you get po4a-translate.
TransTractor::parse() is a virtual function implemented by each module. Here is a little
example to show you how it works. It parses a list of paragraphs, each of them beginning
with <p>.
1 sub parse {
2 PARAGRAPH: while (1) {
3 $my ($paragraph,$pararef,$line,$lref)=("","","","");
4 $my $first=1;
5 while (($line,$lref)=$document->shiftline() && defined($line)) {
6 if ($line =~ m/<p>/ && !$first--; ) {
7 $document->unshiftline($line,$lref);
8
9 $paragraph =~ s/^<p>//s;
10 $document->pushline("<p>".$document->translate($paragraph,$pararef));
11
12 next PARAGRAPH;
13 } else {
14 $paragraph .= $line;
15 $pararef = $lref unless(length($pararef));
16 }
17 }
18 return; # Did not got a defined line? End of input file.
19 }
20 }
On line 6, we encounter <p> for the second time. That's the signal of the next paragraph.
We should thus put the just obtained line back into the original document (line 7) and
push the paragraph built so far into the outputs. After removing the leading <p> of it on
line 9, we push the concatenation of this tag with the translation of the rest of the
paragraph.
This translate() function is very cool. It pushes its argument into the output PO file
(extraction) and returns its translation as found in the input PO file (translation).
Since it's used as part of the argument of pushline(), this translation lands into the
output document.
Isn't that cool? It is possible to build a complete po4a module in less than 20 lines when
the format is simple enough...
You can learn more about this in Locale::Po4a::TransTractor(3pm).
Gettextization: how does it work?
The idea here is to take the original document and its translation, and to say that the
Nth extracted string from the translation is the translation of the Nth extracted string
from the original. In order to work, both files must share exactly the same structure. For
example, if the files have the following structure, it is very unlikely that the 4th
string in translation (of type 'chapter') is the translation of the 4th string in original
(of type 'paragraph').
Original Translation
chapter chapter
paragraph paragraph
paragraph paragraph
paragraph chapter
chapter paragraph
paragraph paragraph
For that, po4a parsers are used on both the original and the translation files to extract
PO files, and then a third PO file is built from them taking strings from the second as
translation of strings from the first. In order to check that the strings we put together
are actually the translations of each other, document parsers in po4a should put
information about the syntactical type of extracted strings in the document (all existing
ones do so, yours should also). Then, this information is used to make sure that both
documents have the same syntax. In the previous example, it would allow us to detect that
string 4 is a paragraph in one case, and a chapter title in another case and to report the
problem.
In theory, it would be possible to detect the problem, and resynchronize the files
afterward (just like diff does). But what we should do of the few strings before
desynchronizations is not clear, and it would produce bad results some times. That's why
the current implementation don't try to resynchronize anything and verbosely fail when
something goes wrong, requiring manual modification of files to fix the problem.
Even with these precautions, things can go wrong very easily here. That's why all
translations guessed this way are marked fuzzy to make sure that the translator reviews
and checks them.
Addendum: How does it work?
Well, that's pretty easy here. The translated document is not written directly to disk,
but kept in memory until all the addenda are applied. The algorithms involved here are
rather straightforward. We look for a line matching the position regexp, and insert the
addendum before it if we're in mode=before. If not, we search for the next line matching
the boundary and insert the addendum after this line if it's an endboundary or before this
line if it's a beginboundary.
FAQ
This chapter groups the Frequently Asked Questions. In fact, most of the questions for now
could be formulated that way: "Why is it designed this way, and not that one?" If you
think po4a isn't the right answer to documentation translation, you should consider
reading this section. If it does not answer your question, please contact us on the
<po4a-devel@lists.alioth.debian.org> mailing list. We love feedback.
Why to translate each paragraph separately?
Yes, in po4a, each paragraph is translated separately (in fact, each module decides this,
but all existing modules do so, and yours should also). There are two main advantages to
this approach:
• When the technical parts of the document are hidden from the scene, the translator can't
mess with them. The fewer markers we present to the translator the less error he can do.
• Cutting the document helps in isolating the changes to the original document. When the
original is modified, finding what parts of the translation need to be updated is eased
by this process.
Even with these advantages, some people don't like the idea of translating each paragraph
separately. Here are some of the answers I can give to their fear:
• This approach proved successfully in the KDE project and allows people there to produce
the biggest corpus of translated and up to date documentation I know.
• The translators can still use the context to translate, since the strings in the PO file
are in the same order than in the original document. Translating sequentially is thus
rather comparable whether you use po4a or not. And in any case, the best way to get the
context remains to convert the document to a printable format since the text formatting
ones are not really readable, IMHO.
• This approach is the one used by professional translators. I agree, that they have
somewhat different goals than open-source translators. The maintenance is for example
often less critical to them since the content changes rarely.
Why not to split on sentence level (or smaller)?
Professional translator tools sometimes split the document at the sentence level in order
to maximize the reusability of previous translations and speed up their process. The
problem is that the same sentence may have several translations, depending on the context.
Paragraphs are by definition longer than sentences. It will hopefully ensure that having
the same paragraph in two documents will have the same meaning (and translation),
regardless of the context in each case.
Splitting on smaller parts than the sentence would be very bad. It would be a bit long to
explain why here, but interested reader can refer to the Locale::Maketext::TPJ13(3pm) man
page (which comes with the Perl documentation), for example. To make short, each language
has its specific syntactic rules, and there is no way to build sentences by aggregating
parts of sentences working for all existing languages (or even for the 5 of the 10 most
spoken ones, or even less).
Why not put the original as comment along with translation (or other way around)?
At the first glance, gettext doesn't seem to be adapted to all kind of translations. For
example, it didn't seemed adapted to debconf, the interface all Debian packages use for
their interaction with the user during installation. In that case, the texts to translate
were pretty short (a dozen lines for each package), and it was difficult to put the
translation in a specialized file since it has to be available before the package
installation.
That's why the debconf developer decided to implement another solution, where translations
are placed in the same file than the original. This is rather appealing. One would even
want to do this for XML, for example. It would look like that:
<section>
<title lang="en">My title</title>
<title lang="fr">Mon titre</title>
<para>
<text lang="en">My text.</text>
<text lang="fr">Mon texte.</text>
</para>
</section>
But it was so problematic that a PO-based approach is now used. Only the original can be
edited in the file, and the translations must take place in PO files extracted from the
master template (and placed back at package compilation time). The old system was
deprecated because of several issues:
• maintenance problems
If several translators provide a patch at the same time, it gets hard to merge them
together.
How will you detect changes to the original, which need to be applied to the
translations? In order to use diff, you have to note which version of the original you
translated. I.e., you need a PO file in your file ;)
• encoding problems
This solution is viable when only European languages are involved, but the
introduction of Korean, Russian and/or Arab really complicate the picture. UTF could
be a solution, but there are still some problems with it.
Moreover, such problems are hard to detect (i.e., only Korean readers will detect that
the encoding of Korean is broken [because of the Russian translator])
gettext solves all those problems together.
But gettext wasn't designed for that use!
That's true, but until now nobody came with a better solution. The only known alternative
is manual translation, with all the maintenance issues.
What about the other translation tools for documentation using gettext?
As far as I know, there are only two of them:
poxml
This is the tool developed by KDE people to handle DocBook XML. AFAIK, it was the
first program to extract strings to translate from documentation to PO files, and
inject them back after translation.
It can only handle XML, and only a particular DTD. I'm quite unhappy with the handling
of lists, which end in one big msgid. When the list become big, the chunk becomes
harder to shallow.
po-debiandoc
This program done by Denis Barbier is a sort of precursor of the po4a SGML module,
which more or less deprecates it. As the name says, it handles only the DebianDoc DTD,
which is more or less a deprecated DTD.
The main advantages of po4a over them are the ease of extra content addition (which is
even worse there) and the ability to achieve gettextization.
Educating developers about translation
When you try to translate documentation or programs, you face three kinds of problems;
linguistics (not everybody speaks two languages), technical (that's why po4a exists) and
relational/human. Not all developers understand the necessity of translating stuff. Even
when good willed, they may ignore how to ease the work of translators. To help with that,
po4a comes with lot of documentation which can be referred to.
Another important point is that each translated file begins with a short comment
indicating what the file is, how to use it. This should help the poor developers flooded
with tons of files in different languages they hardly speak, and help them dealing
correctly with it.
In the po4a project, translated documents are not source files anymore. Since SGML files
are habitually source files, it's an easy mistake. That's why all files present this
header:
| *****************************************************
| * GENERATED FILE, DO NOT EDIT *
| * THIS IS NO SOURCE FILE, BUT RESULT OF COMPILATION *
| *****************************************************
|
| This file was generated by po4a-translate(1). Do not store it (in VCS,
| for example), but store the PO file used as source file by po4a-translate.
|
| In fact, consider this as a binary, and the PO file as a regular source file:
| If the PO gets lost, keeping this translation up-to-date will be harder ;)
Likewise, gettext's regular PO files only need to be copied to the po/ directory. But this
is not the case of the ones manipulated by po4a. The major risk here is that a developer
erases the existing translation of his program with the translation of his documentation.
(Both of them can't be stored in the same PO file, because the program needs to install
its translation as an mo file while the documentation only uses its translation at compile
time). That's why the PO files produced by the po-debiandoc module contain the following
header:
#
# ADVISES TO DEVELOPERS:
# - you do not need to manually edit POT or PO files.
# - this file contains the translation of your debconf templates.
# Do not replace the translation of your program with this !!
# (or your translators will get very upset)
#
# ADVISES TO TRANSLATORS:
# If you are not familiar with the PO format, gettext documentation
# is worth reading, especially sections dedicated to this format.
# For example, run:
# info -n '(gettext)PO Files'
# info -n '(gettext)Header Entry'
#
# Some information specific to po-debconf are available at
# /usr/share/doc/po-debconf/README-trans
# or http://www.debian.org/intl/l10n/po-debconf/README-trans
#
SUMMARY of the advantages of the gettext based approach
• The translations are not stored along with the original, which makes it possible to
detect if translations become out of date.
• The translations are stored in separate files from each other, which prevents
translators of different languages from interfering, both when submitting their patch
and at the file encoding level.
• It is based internally on gettext (but po4a offers a very simple interface so that you
don't need to understand the internals to use it). That way, we don't have to re-
implement the wheel, and because of their wide use, we can think that these tools are
more or less bug free.
• Nothing changed for the end-user (beside the fact translations will hopefully be better
maintained). The resulting documentation file distributed is exactly the same.
• No need for translators to learn a new file syntax and their favorite PO file editor
(like Emacs' PO mode, Lokalize or Gtranslator) will work just fine.
• gettext offers a simple way to get statistics about what is done, what should be
reviewed and updated, and what is still to do. Some example can be found at those
addresses:
- http://kv-53.narod.ru/kaider1.png
- http://www.debian.org/intl/l10n/
But everything isn't green, and this approach also has some disadvantages we have to deal
with.
• Addenda are... strange at the first glance.
• You can't adapt the translated text to your preferences, like splitting a paragraph
here, and joining two other ones there. But in some sense, if there is an issue with the
original, it should be reported as a bug anyway.
• Even with an easy interface, it remains a new tool people have to learn.
One of my dreams would be to integrate somehow po4a to Gtranslator or Lokalize. When an
SGML file is opened, the strings are automatically extracted. When it's saved a
translated SGML file can be written to disk. If we manage to do an MS Word (TM) module
(or at least RTF) professional translators may even use it.
AUTHORS
Denis Barbier <barbier,linuxfr.org>
Martin Quinson (mquinson#debian.org)