[developers] More TDL cobwebs

goodman.m.w at gmail.com goodman.m.w at gmail.com
Fri Sep 7 20:59:28 CEST 2018

Thanks for the feedback, John,

While I appreciate your arguments and code, I am reluctant to agree with
any changes now. The LKB has been a pioneer in allowing docstrings, but I
don't think we should revert the work other developers have put into their
processors in the last month, not to mention the hard-earned consensus over
the color of this bike shed. Here are my reasons:

1. The agreed-upon syntax does not break backward compatibility (except
regarding the number of quote characters), it only opens up new places
where docstrings may occur (see (3))

2. The lack of support for docstrings outside of the LKB hindered their
adoption, so backward compatibility isn't much of an issue given that
grammar developers avoided using them (given this, maybe I should have
pushed harder for docstrings immediately after := or :+... oh well).

3. The LKB's implementation that parses supertypes (or "parents" as used in
the lisp code) before other terms is only half-baked. It first reads some
type names, then looks for a docstring, then reads other terms, which may
include more type names. I proposed making a change to the syntax so that
type names must appear before other terms in a top-level conjunction, but
the only replies I got addressing this point (from Stephan and Dan) opposed
such a change. Thus, we agreed that type names have no special position in
conjunctions. Because of this, saying that the docstring must occur before
the AVM means little, because (a) the AVM may appear before a type name,
and (b) there may be more than one AVM. For instance, the LKB (with the
ERG's triple-quoted patch) currently accepts these:

    a := b & c """doc""".
    a := b & """doc""" c.
    a := b & c & """doc""" [ Q r ].
    a := b & """doc""" c & [ Q r ].
    a := b & """doc""" [ Q r ] & c.

but not these:

    a := """doc""" b & c.
    a := """doc""" b & c & [ Q r ].
    a := b & c & [ Q r ] """doc""".

Furthermore, it accepts:

    a := b & c & [ Q r ].
    a := b & [ Q r ] & c.

but not:

    a := [ Q r ] & b & c.

I imagine a grammar developer (who doesn't browse the lisp code) would not
find these facts consistent. It should either enforce that all supertypes
appear before other terms, or allow them to mix freely.

So, on the one hand, I think that the LKB is currently deficient WRT the
above patterns (which are all allowed, according to current consensus). I
may take a look at fixing the Lisp code, but it would take me a while. On
the other hand, the LKB merely enforces the conventional layout of TDL
definitions, so it is unlikely to cause problems for now.

Finally, docstrings are desired for more than just the ERG, so the
temporary solution in patches.lsp should eventually make it into the LKB
proper. For instance, the read-tdl-avm-def and read-tdl-conjunction
functions would need some changes and the read-tdl-type-parents function
should probably just be removed.

On Fri, Sep 7, 2018 at 4:58 AM John Carroll <J.A.Carroll at sussex.ac.uk>

> Hi,
> I've been looking at TDL reading in the LKB, and (partly for pragmatic
> reasons) I suggest restricting docstrings to occur only in the position
> immediately preceding the AVM - or just before the final . terminator if
> there is no AVM. Here are my reasons:
> 1. The LKB currently only allows docstrings in that position, and changing
> this while retaining backward compatibility would require an unreasonable
> amount of patching in a grammar lkb/patches.lsp file
> 2. This position is analogous to where docstrings are allowed in
> programming languages / docstring packages
> In the hope that this is acceptable, at least for the time being, I've
> sent Dan a new version of his patch to change docstrings from double-quoted
> to triple double-quoted in the LKB. The patch is attached in case other
> grammar developers want to pick it up.
> John
> On 7 Sep 2018, at 00:29, goodman.m.w at gmail.com wrote:
> Hi all,
> There are some remaining issues with TDL that I'd like to clean up. First
> I will summarize some decisions made (or at least not rejected) in previous
> email threads:
> 1. Supertypes appear before other terms in a conjunction only by
> convention (not enforced in the syntax)
> 2. Docstrings are triple-quoted and may appear before any top-level term
> or before the final . terminator
> 3. Comments may appear in definitions anywhere that spaces can, except
> within strings/regexes/affixing-patterns
> The following changes are things I think people agree with, so I'd like to
> consider them as decided:
> 4. Removal of the :< operator (if accepted as a variant of :=, throw a
> warning)
> 5. Removal of 'single-quoted-symbols
> 6. Removal of double-quoted "docstrings"
> 7. Removal of non-regex uses of ^ (otherwise any BNF of TDL is necessarily
> incomplete because the "extended-syntax" use of ^ is open-ended)
> And there's at least one point I don't think we reached a decision on:
> 8. Instances must have exactly 1 "supertype" (which is really just a type
> and not a supertype, i.e., it doesn't change the type hierarchy)
> Also:
> 9. Does anyone know how wild-cards differ from letter-sets? I see HaG has
> a wild-card and suffix pattern like these:
>     %(wild-card (?g ui))
>     ...
>     %suffix (!c!v !c!vn) (!v?g !vn)
> My guess is that wild-cards match but are not used in the replacement,
> which I can imagine is useful if you want the replacement to use the second
> of two matches but not the first. It makes me wonder why we don't just use
> regex substitutions for these things.
> If nobody responds about (1)--(7), I'll make sure the syntax description
> on the TdlRfc wiki reflects those decisions.
> --
> -Michael Wayne Goodman

-Michael Wayne Goodman
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