Hi Michael,

thanks for the explanation and paper link!

Regards,

Chun

> Il giorno 20 mag 2018, alle ore 11:56, michael.norr...@data61.csiro.au ha 
> scritto:
> 
> The paper describing the work in examples/logic/ltl will appear at ITP this 
> year.  Because there's a slight CakeML angle to it, it's available from 
> cakeml.org at https://cakeml.org/itp18.pdf.
> 
> You are right that this work could be described as a deep embedding.
> 
> Deep embeddings usually have the advantage that you can describe algorithms 
> on the syntax, and not just have to think about the semantic values. For 
> example, you can describe the NNF transformation when you have a deep 
> embedding, but the best option for something similar with a shallow embedding 
> is a statement of some equivalences between different semantic formulations 
> of the same thing.
> 
> It's also obviously useful to have a type corresponding to the syntax if you 
> are going to define computable functions to traverse over it and transform it 
> into automata (as is done in our work).
> 
> Michael
> 
> On 19/5/18, 00:42, "Chun Tian" <binghe.l...@gmail.com> wrote:
> 
>    Hi,
> 
>    I saw how the new LTL formalization (in `examples/logic/ltl`) by Simon 
> Jantsch suddenly appeared in the past months and because more and more 
> complete also with help of HOL maintainers. But there’s already an older LTL 
> formalization (in `src/temporal`) since long time ago, done by Klaus 
> Schneider et al. [1]
> 
>    My first question: is there a paper (in PDF, published or unpublished) 
> documenting the work in `examples/logic/ltl` so that I can learn beside 
> looking at raw HOL scripts?
> 
>    Second question: regarding the difference between two versions of LTL 
> formalizations, can I say the work in `examples/logic/ltl` is a *deep* 
> embedding? (because it has to define the LTL syntax by a datatype:
> 
>    val _ = Datatype`
>      ltl_frml
>      = VAR 'a
>      | N_VAR 'a
>      | DISJ ltl_frml ltl_frml
>      | CONJ ltl_frml ltl_frml
>      | X ltl_frml
>      | U ltl_frml ltl_frml
>      | R ltl_frml ltl_frml`;
>    )
> 
>       while the work in `src/temporal` is *shallow* embedding? (because it 
> embeds LTL term into HOL as ``:num -> bool`` without using any datatype)
> 
>       and if so, what’s the pros and cons for choosing one of them as a 
> working basis (for proving further results)?
> 
>    Third question: is there a way to connect the two versions of LTL, so that 
> LTL theorems proved from one side can be (somehow) automatically translated 
> into theorems on the other side?
> 
>    Regards,
> 
>    Chun
> 
>    [1] Schneider, K., Hoffmann, D.W.: A HOL Conversion for Translating Linear 
> Time Temporal Logic to ω-Automata. In: Bassiliades, N., Gottlob, G., Sadri, 
> F., Paschke, A., and Roman, D. (eds.) LNCS 9202 - Rule Technologies: 
> Foundations, Tools, and Applications. pp. 255–272. Springer Berlin 
> Heidelberg, Berlin, Heidelberg (1999).
> 
> 
> 
> 
> 
> 
> 
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