[developers] Questions on the syntax of TDL

Thu Jul 12 02:00:52 CEST 2018

Thank you, Bernd, for the feedback. But I'm not having success parsing
types with docstrings using PET. E.g., I changed sign-min in the ERG like
this:

    sign_min := *avm* &
      "doc"
      [ SYNSEM synsem_min,
        KEY-ARG bool ].

But flop doesn't like it:

    goodmami at tpy:~/grammars/erg$ flop english.tdl
    reading `Version.lsp'...
    converting `english.tdl' (ERG (1214)) into `english.grm' ...
    loading `english.tdl'... including `fundamentals.tdl'...
fundamentals.tdl:21:3: error: (syntax) - got `                   [',
expecting `.' at end of type definition
    [...]

I get similar errors no matter where I put it (before :=, directly after
:=, after ]). It's syntactically valid if I have ... *avm* & "doc" & ...,
but then it has trouble unifying (as expected).

It does, however, seem to be happy having a comment there (both ; and #|
styles) instead of a doc string.

I'm using flop version 0.99.14svn_cm from the LOGON distribution.

On Wed, Jul 11, 2018 at 7:00 AM, Bernd Kiefer <Bernd.Kiefer at dfki.de> wrote:

> Concerning question 3, at least in TDL and PET there was no such
> restriction,
> but that could make the definition of docstrings easier.
>
> Best,
>
> Bernd
>
> On 11.07.2018 03:01, Michael Wayne Goodman wrote:
>
> I attempted to define a BNF-like description of TDL syntax on the wiki:
> http://moin.delph-in.net/TdlRfc
> I tried to follow the partial BNF in the LKB source and often referred to
> the lisp code itself in order to fill out the rest of the description.
>
> My 3 questions above are concisely repeated at the bottom of the wiki
> along with some others.
>
> I welcome corrections and discussion (here or on the wiki) from any TDL
> nerds or authorities (especially if you've written a TDL parser).
>
> On Mon, Jul 9, 2018 at 12:49 PM, Michael Wayne Goodman <goodmami at uw.edu>
> wrote:
>
>> Hi developers,
>>
>> I'm taking a closer look at the syntax of TDL files and the situation is
>> a bit of a mess. Can anyone help me clarify some things? (I'll restrict
>> myself to 3 questions for now)
>>
>> The Copestake 2002 reference (Implementing TFS Grammars) has a BNF for
>> TDL, but it's a bit out of date and, according to comments in the LKB
>> source code, incorrect in parts. The LKB source comments are scattered,
>> incomplete, inconsistent, and also a bit outdated. There is not much on the
>> wiki. There is some discussion in the mailing list archives (much from
>> before my time in DELPH-IN), but it's not clear how current those
>> descriptions are.
>>
>> Q1: Are supertypes special in a definition?
>>
>> The BNF (in the LKB source) says this:
>>
>>     Type-def -> Type { Avm-def | Subtype-def} . |
>>                          Type { Avm-def | Subtype-def}.
>>     Avm-def -> := Conjunction | Comment Conjunction
>>     Conjunction -> Term { & Term } *
>>     Term -> Type | Feature-term | Diff-list | List | Coreference
>>
>> That makes it sound like I could do this:
>>
>>     mytype := [ FEAT val ] & supertype.
>>
>> or even:
>>
>>     mytype := <! diff list.. !> & #coref & supertype.
>>
>> But elsewhere it seems like a list of parents is special and appears
>> before the rest of the conjunction. E.g., at read-tdl-avm-def of
>> lingo/lkb/src/io-tdl/tdltypeinput.lsp I see this alternate definition of
>> Avm-def:
>>
>>   ;;; Avm-def -> := Parents Conjunction | Parents Comment Conjunction |
>>   ;;;               Parents | Parents Comment
>>
>> It seems that both ACE and PET are fine with putting supertypes after the
>> feature list (and some other variations). I'm fine with this, but I wonder
>> what it means for docstrings (see Q3 below), which (I think) are supposed
>> to appear after the list of parents and before the feature list.
>>
>>
>> Q2: Subtype-def is now just a variant of Avm-def, yes?
>>
>> The BNF still describes subtyping (with the :< operator) as only taking a
>> single parent:
>>
>>     Subtype-def ->  :< type
>>
>> But I believe the consensus is that this is unnecessary (it's equivalent
>> to using := with only a supertype), so :< is treated as equivalent to :=
>> (to avoid breaking backward compatibility). Is this interpretation used by
>> all processors?
>>
>>
>> Q3: What's the final word with type comments / docstrings?
>>
>> I find evidence of 3 proposed variants: (1) a block of ";" comments
>> before a typename (LTDB-style); (2) a block of ";" comments within a type
>> description; and (3) a "doc string" within a type description. Furthermore,
>> there is a question as to whether comments or strings within a type go
>> after the ":=" or after the list of supertypes. I think #| ... |# comments
>> were not considered for this purpose.
>>
>> My guess is this:
>>
>> * LTDB-style comments (before the type identifier) are processed
>> separately from TDL-parsing
>> * type-internal comments can go anywhere but are discarded
>> * type-internal doc strings must appear after the list of supertypes and
>> are later available for inspection (they are included as a non-functional
>> part of a type)
>>
>> ACE seems happy with my assumptions, although PET doesn't seem to like
>> doc strings at all.
>>
>>
>> Thanks!
>>
>> --
>> Michael Wayne Goodman
>>
>
>
>
> --
> Michael Wayne Goodman
>
>
> --
> ----------------------------------------------------------------------
> Bernd Kiefer     DFKI GmbH,  Stuhlsatzenhausweg,  D-66123 Saarbrueckenkiefer at dfki.de   +49-681/85775-5301 (phone)   +49-681/85775-5338 (fax)
> ----------------------------------------------------------------------
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-- 
Michael Wayne Goodman
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