The <section> element in a dix file can be of type standard, inconditional, postblank or preblank.
The section type is used to change how tokenisation works.
Normally, analysis must be separated by spaces (or other blanks), but an analysis in an 'inconditional' section can appear right after or before other analyses ('standard' or non-standard) or even right next to unknowns. The 'inconditional' section of a dictionary typically contains punctuation, and such things.
In detail: Analysis in lttoolbox works in a left-to-right longest match fashion. We read characters from input, trying to match them in the transducer, and if we've reached a final transition when at the "end" of the input word, we can output the analysis (or we can try matching something even longer, but if not we use the match we found). But how do we know when we're at the end of an input word? Any "blank" character (not in <alphabet> in .dix files) is allowed to separate words, so e.g. spaces or other strange characters can separate words. But we may also say that certain words-with-analyses can separate words – to mark an analysis as "may act as word-separator", we put it in the 'inconditional' section.
$ echo 23men |apertium -d . en-it-anmor ^23/23<num>$^men/man<n><pl>$^./.<sent>$
In the above, we don't need the space between 23 and men because numbers are in an 'inconditional' section.
We can get some weird effects by putting plain characters in 'inconditional':
<dictionary> <alphabet>ab</alphabet> <sdefs> <sdef n="aa"/> <sdef n="ab"/> </sdefs> <section id="foo" type="inconditional"> <e><p><l>a</l><r>a<s n="aa"/></r></p></e> <e><p><l>aa</l><r>aa<s n="aa"/></r></p></e> </section> </dictionary> $ echo aaa |lt-proc sample.bin ^aa/aa<aa>$^a/a<aa>$ $ echo aaaa |lt-proc sample.bin ^aa/aa<aa>$^aa/aa<aa>$ $ echo aaaaa |lt-proc sample.bin ^aa/aa<aa>$^aa/aa<aa>$^a/a<aa>$
postblank / preblank
The postblank and preblank sections work exactly like inconditional with respect to how they tokenise the input. The only difference is that anything in a postblank section will make lt-proc output a space after the token (in preblank, before the token).
So if "☃" is in postblank (tagged sent), and "foo" and "bar" are in a regular section (tagged n), then we get:
$ echo 'foo☃bar' | lt-proc analyser.bin ^foo/foo<n>$^☃/☃<sent>$ ^bar/bar<n>$
If "☃" were in preblank, we'd get:
$ echo 'foo☃bar' | lt-proc analyser.bin ^foo/foo<n>$ ^☃/☃<sent>$^bar/bar<n>$
Why is this useful?