[developers] Questions on the syntax of TDL

[Woodley Packard]

2 cents worth...

1. I think the logical behavior for an addendum with a doc string is concatenation, not replacement.  The doc string on the addendum should document what the addendum adds to the type, not the whole type.

2. ACE (I believe) allows comments just about anywhere in TDL.  I find this very useful when editing TDL, e.g. annotating changes on a fine grained level or disabling certain constraints temporarily without deleting them.

Regards,
Woodley

> On Jul 11, 2018, at 5:00 PM, Michael Wayne Goodman <goodmami at uw.edu> wrote:
> 
> 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
>> 
>> -- 
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> 
> 
> 
> -- 
> Michael Wayne Goodman
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