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Paul Taylor | 1 Nov 2007 13:57
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DVI, PDF and TAC

Mike Barr reported
	that Adobe Acrobat 8 tacitly suppresses all ligature glyphs of the
	fi, fl, ff, ffi, and ffl sort and displays blanks in their place
and then that
	I have to admit that I never tested it, just copied the complaint
	from texhax
but nevertheless this presumably gives us some idea why,
	at TAC, we still consider the dvi to be the official format.

However, as I shall demonstrate, the rest of the world nowadays regards
PDF as the standard format in which to publish technical documents.

DVI (the normal output from LaTeX) was based on the 1950s Monotype
typesetting system, and puts characters from various fonts at given
positions on the page, but cannot rotate them, and has no graphics
capability.  The fonts also have to be supplied separately.   On the
other hand, it has the virtues of being a compact and simple format
that future digital archeologists would have no difficulty in
deciphering.

Adobe's PDF and PostScript have general graphics capability.

By insisting on DVI, "Theory and Applications of Categories" severely
limits the ways in which authors can express their mathematical ideas.
But its restrictions go further than this:  the use of ANY macro package
other than those by Mike Barr and Kris Rose is forbidden!

Does anyone know of another journal that publishes primarily in DVI?

One candidate might be the journal of the TeX Users' Group,
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Bob Rosebrugh | 1 Nov 2007 16:35
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Diplay Formats

This is to invoke a limit on the current categories discussion of document
display formats to the next 48 hours. Paul's post redirects the discussion
towards indirectly categorical relevance, but there are other forums where
such matters are not peripheral.

A brief comment on the Triassic tendencies of TAC and its editors will
follow.

regards to all, Bob
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Toby Bartels | 1 Nov 2007 17:47
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Surjective equivalences (Was: Historical terminology,.. and a few other things.)

Jean Benabou wrote in part:

>Surjective equivalences are much better than mere equivalences because :

I would be grateful for a reference or list of references
about "important properties and what they are good for"
for surjective equivalences.

--Toby
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Bob Rosebrugh | 2 Nov 2007 01:56
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Re: DVI, PDF and TAC


With regrets that this response is not briefer...

On Thu, 1 Nov 2007, Paul Taylor wrote:

> Does anyone know of another journal that publishes primarily in DVI?

Many electronic journals in mathematics post dvi files. Like TAC, most
of these post, and also archive, all of dvi, ps and pdf.

TAC's policy on dvi has evolved since 1995. That policy will continue to
change, no doubt at a slower rate than some would wish. None of us knows
what the digital world will look like in 10 years, but careful choices
made for TAC over a dozen years ago have been validated.

> Maybe Bob Rosebrugh could tell us how many downloads there have
> been in the various formats from the main TAC web site at MTA.

Inevitably nowadays, most of the web traffic on sites like TAC's is for
caching, so such figures for any TAC site mean nothing. If Paul's counts
record human usage, then what is surprising is how many of the downloads
were *not* pdf.

...

> Why does he create so much inconvenience for TAC authors for such
> a trivial benefit to himself?

This request (for a single source file) is seen as, at worst, a trivial
inconvenience by most authors, and it simplifies the lives of editors who
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Tarmo Uustalu | 2 Nov 2007 18:37
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TYPES small workshop on Effects and Type Theory


In the frame of the extended EU FP6-funded TYPES project, we are
organizing an ad hoc "small workshop" on integration of effects into
type-theoretic programming/reasoning.

This is an informal event and attendance is not confined to people
involved in TYPES. On the contrary, attendance and contributions from
outside the TYPES consortium are most welcome. The invited speakers
are Paul Levy and Aleksandar Nanevski.

---

              Call for contibutions and participation

            Workshop on Effects and Type Theory,  EffTT
               Tallinn, Estonia, 13-14 December 2007

                       http://cs.ioc.ee/efftt/

              a "small workshop" of the TYPES project

Background

The syntax and semantics of impurities of computation known as effects
have been an important challenge for functional programming. Today, we
tend to employ categorically inspired tools such as monads, Lavwere
theories and arrows, but also more pragmatic approaches such as
uniqueness typing.

Effects are an issue also for type-theoretic programming and
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Clemens Kupke | 2 Nov 2007 16:26
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CMCS 2008: First call for papers

9th International Workshop on Coalgebraic Methods in Computer Science
                http://www.cwi.nl/projects/cmcs08/
                         Budapest, Hungary
                          April 4-6, 2008

The workshop will be held in conjunction with the 11th European Joint
     Conferences on Theory and Practice of Software ETAPS 2008
                        March 29 - April 6, 2008

Aims and Scope

During the last few years, it has become increasingly clear that a
great variety of state-based dynamical systems, like transition
systems, automata, process calculi and class-based systems, can be
captured uniformly as coalgebras.  Coalgebra is developing into a
field of its own interest presenting a deep mathematical foundation, a
growing field of applications and interactions with various other
fields such as reactive and interactive system theory, object oriented
and concurrent programming, formal system specification, modal logic,
dynamical systems, control systems, category theory, algebra,
and analysis. The aim of the workshop is to bring together
researchers with a common interest in the theory of coalgebras and its
applications.

The topics of the workshop include, but are not limited to:

      the theory of coalgebras (including set theoretic and
          categorical approaches);
      coalgebras as computational and semantical models (for
          programming languages, dynamical systems, etc.);
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wlawvere | 2 Nov 2007 17:12
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Re: Comma categories


Dear Uwe
You are right in thinking that there should be such 
an exposition because the construction is explicitly 
or implicitly involved in so many contexts that a 
formal summary would be useful. Unfortunately, 
I know of no such exposition though Hugo Volger 
started one many years ago.

As you can see from the TAC Reprint of my 
thesis, the original motivation was to 
be able to state the definition of adjointness in a 
wholly elementary way for arbitrary categories 
without involving enrichments in some fixed
category of sets. If A is a reflective subcategory in 
some X and if B is coreflective in the same X, then 
composing the implicit functors yields an adjoint 
pair between A and B. The point is that conversely 
any adjoint pair can be so factored through a third 
"adjunction" category X and the universally available 
choice has this simple construction as a pullback.
It proved to be the appropriate tool for calculating
Kan extensions, adequacy comonads, fibrations,etc.
Grothendieck defined slice categories and Artin the 
gluing, both of which are special cases of this
construction.

Although inserters are interdefinable (like equalizers
vs pullbacks), some consider inserters more basic: 
given x:A->C and y:B->C, one can take the
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Jiri Adamek | 2 Nov 2007 12:44
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Functor derivatives - a question and a result

Andre Joyal defined derivatives of analytic functors
in his 1986 paper. Recently I heard the more general definition
of a derivative F' of an endofunctor F defined via a universal
sub-cartesian transformation from F'xId into F. Who is the author
of this definition? The following result seems to indicate that
outside of the realm of analytic functors derivatives may not
be really useful:

Theorem. Every non-faithful functor F:Set -> Set has the derivative
         F' = 0 (the constant functor to the empty set).

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
alternative e-mail address (in case reply key does not work):
J.Adamek <at> tu-bs.de
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JeanBenabou | 2 Nov 2007 02:55
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References

Dear colleagues,

I hope someone, and in particular Prof. Peter Johnstone, will help me
with the following information. I thought I had, with Jacques
Roubaud, proved in our joint note at the "Comptes Rendus" which I
mentioned in my previous mail proved a theorem on Monads and Descent.
I must have been mistaken, and also the many persons who quoted this
note, because in El Proposition 1.5.5 is the same theorem, but
attributed to J. Beck.

I immediately "rushed" to the monumental bibliography of El to find
the reference, and there, big surprise, there was no J. Beck at all
among the 1262 references.

Thus i'd greatly appreciate to have the date and paper of the paper
where Beck proved this theorem, and the precise statement he made, in
particular, did he prove his theorem in the general context of
fibered or indexed categories, or only in some very special case.

Many thanks for your help
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Ross Street | 3 Nov 2007 10:03
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Apropos a couple of current topics

History can be harder than mathematics. Yet, it is a worthy goal to get it
right. This can require discussion and feedback. Here are some of my
memories which I am quite happy for people to correct if they have a
fuller picture.

Jean Benabou invented bicategories. In SLNM47 you will find
the particular example of a bicategory Spn(E) whose morphisms
are spans in a pullback-complete category E. You will also find the
convention to refer to properties holding in the homs as local. I always
thought it nice that the homs in Spn(E) were slice categories
E / a x b, thereby unifying two uses of "local".

You will also find in that SLNM47 paper, the notion of morphism of
bicategories and of homomorphism of bicategory. These a very useful
concepts. They do compose in their own way. I believe there was no
attempt to deny that the "indexed categories" of Pare-Schumacher
are category-valued homomorphisms.

The 1969-70 academic year at Tulane University Math Dept was dedicated to
Category Theory. Jack Duskin and I were there (doing some teaching as well
as research) for the whole year. Saunders Mac Lane and Eduardo Dubuc were
there for the first semester. Bernhard Banaschewski and Z.  Hedrln were
there for the second semester. However, we had a lot of visitors as well.
In particular, Jean Benabou visited sometime in the first semester.  In
particular, I learnt from Benabou's lectures about the "Chevalley
condition" for fibrations and how descent data were Eilenberg-Moore
algebras. Jean gave me a copy of his Comptes Rendu article with Jacques
Roubaud.

Very soon after Jean Benabou left, Jon Beck arrived. He asked me what the
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Gmane