@string{brics =	"{BRICS}"}
@string{daimi =	"Department of Computer Science, University of Aarhus"}
@string{iesd  =	"Department of Computer Science, Institute
of Electronic Systems, Aalborg University"}
@string{rs    =	"Research Series"}
@string{ns    =	"Notes Series"}
@string{ls    =	"Lecture Series"}
@string{ds    =	"Dissertation Series"}

@techreport{BRICS-RS-00-52,
author = 	 "Cr{\'e}peau, Claude and L{\'e}gar{\'e},
Fr{\'e}d{\'e}ric and Salvail, Louis",
title = 	 "How to Convert a Flavor of Quantum Bit
Commitment",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-52",
month = 	 dec,
note = 	 "24~pp. Appears in " # lncs2045 # ", pages
60--77",
abstract = 	 "In this paper we show how to convert a
statistically binding but computationally
concealing quantum bit commitment scheme into a
computationally binding but statistically
concealing scheme. For a security parameter
$n$, the construction of the statistically
concealing scheme requires $O(n^2)$ executions
of the statistically binding scheme. As a
consequence, statistically concealing but
computationally binding quantum bit commitments
can be based upon any family of quantum one-way
functions. Such a construction is not known to
exist in the classical world",
}
@techreport{BRICS-RS-00-51,
author = 	 "Mosses, Peter D.",
title = 	 "{CASL} for {CafeOBJ} Users",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-51",
month = 	 dec,
note = 	 "25~pp. Appears in " # ecafe00 # ", chapter 6,
pages 121--144",
abstract = 	 "CASL is an expressive language for the
algebraic specification of software
requirements, design, and architecture. It has
been developed by an open collaborative effort
called CoFI (Common Framework Initiative for
algebraic specification and development). CASL
combines the best features of many previous
main-stream algebraic specification languages,
and it should provide a focus for future
research and development in the use of
algebraic techniques, as well facilitating
interoperability of existing and future
tools.\bibpar
This paper presents CASL for users of the
CafeOBJ framework, focussing on the
relationship between the two languages. It
first considers those constructs of CafeOBJ
that have direct counterparts in CASL, and then
(briefly) those that do not. It also motivates
various CASL constructs that are not provided
by CafeOBJ. Finally, it gives a concise
overview of CASL, and illustrates how some
CafeOBJ specifications may be expressed in
CASL.",
}

@techreport{BRICS-RS-00-50,
author = 	 "Mosses, Peter D.",
title = 	 "Modularity in Meta-Languages",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-50",
month = 	 dec,
note = 	 "19~pp. Appears in " # inrialfm00 # ", pages
1--18",
abstract = 	 "A meta-language for semantics has a high
degree of modularity when descriptions of
individual language constructs can be
formulated independently using it, and do not
require reformulation when new constructs are
added to the described language. The quest for
modularity in semantic meta-languages has been
going on for more than two decades.\bibpar
Here, most of the main meta-languages for
operational, denotational, and hybrid styles of
semantics are compared regarding their
modularity. A simple bench-mark is used:
describing the semantics of a pure functional
language, then extending the described language
with references, exceptions, and concurrency
constructs. For each style of semantics, at
least one of the considered meta-languages
appears to provide a high degree of
modularity.",
}

@techreport{BRICS-RS-00-49,
author = 	 "Kohlenbach, Ulrich",
title = 	 "Higher Order Reverse Mathematics",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-49",
month = 	 dec,
note = 	 "18~pp. To appear in S.~G. Simpson (ed.), {\em
Reverse Mathematics}",
abstract = 	 "In this paper we argue for an extension of the
second order framework currently used in the
program of reverse mathematics to finite types.
In particular we propose a conservative finite
type extension RCA$^{\omega}_0$ of the second
order base system RCA$_0$. By this conservation
nothing is lost for second order statements if
we reason in RCA$^{\omega}_0$ instead of
RCA$_0$. However, the presence of finite types
allows to treat various analytical notions in a
rather direct way, compared to the encodings
needed in RCA$_0$ which are not always provably
faithful in RCA$_0$. Moreover, the language of
finite types allows to treat many more
principles and gives rise to interesting
extensions of the existing scheme of reverse
mathematics. We indicate this by showing that
the class of principles equivalent (over
RCA$^{\omega}_0$) to Feferman's
non-constructive $\mu$-operator forms a
mathematically rich and very robust class. This
is closely related to a phenomenon in higher
type recursion theory known as Grilliot's
trick",
}
@techreport{BRICS-RS-00-48,
author = 	 "Jurdzi{\'n}ski, Marcin and V{\"o}ge, Jens",
title = 	 "A Discrete Stratety Improvement Algorithm for
Solving Parity Games",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-48",
month = 	 dec,
note = 	 "31~pp. Extended abstract appears in " # lncs1855 # ",
pages 202--215",
abstract = 	 "A discrete strategy improvement algorithm is
given for constructing winning strategies in
parity games, thereby providing also a new
solution of the model-checking problem for the
modal $\mu$-calculus. Known strategy
improvement algorithms, as proposed for
stochastic games by Hoffman and Karp in 1966,
and for discounted payoff games and parity
games by Puri in 1995, work with real numbers
and require solving linear programming
instances involving high precision arithmetic.
In the present algorithm for parity games these
difficulties are avoided by the use of discrete
vertex valuations in which information about
the relevance of vertices and certain distances
is coded. An efficient implementation is given
for a strategy improvement step. Another
advantage of the present approach is that it
provides a better conceptual understanding and
easier analysis of strategy improvement
algorithms for parity games. However, so far it
is not known whether the present algorithm
works in polynomial time. The long standing
problem whether parity games can be solved in
polynomial time remains open",
}

@techreport{BRICS-RS-00-47,
author = 	 "Nielsen, Lasse R.",
title = 	 "A Denotational Investigation of
Defunctionalization",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-47",
month = 	 dec,
note = 	 "50~pp. Presented at {\em 16th Workshop on the
Mathematical Foundations of Programming
Semantics}, {MFPS~'00} (Hoboken, New Jersey,
USA, April 13--16, 2000)",
abstract = 	 "Defunctionalization has been introduced by
John Reynolds in his 1972 article {\em
Definitional Interpreters for Higher-Order
Programming Languages}. Its goal is to
transform a higher-order program into a
first-order one, representing functional values
as data structures. Even though
defunctionalization has been widely used, we
observe that it has never been proven correct.
We formalize defunctionalization denotationally
for a typed functional language, and we prove
that it preserves the meaning of any
terminating program. Our proof uses logical
relations",
}

@techreport{BRICS-RS-00-46,
author = 	 "Yang, Zhe",
title = 	 "Reasoning About Code-Generation in Two-Level
Languages",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-46",
month = 	 dec,
note = 	 "74~pp",
abstract = 	 "This paper shows that two-level languages are
not only a good tool for describing
code-generation algorithms, but a good tool for
reasoning about them as well. Common proof
obligations of code-generation algorithms in
the form of two-level programs are captured by
certain general properties of two-level
languages.\bibpar
To prove that the generated code behaves as
desired, we use an {\em erasure} property,
which equationally relates the generated code
to an erasure of the original two-level program
in the object language, thereby reducing the
two-level proof obligation to a simpler
one-level obligation. To prove that the
generated code satisfies certain syntactic
constraints, e.g., that it is in some normal
form, we use a {\em type-preservation} property
for a refined type system that enforces these
constraints. Finally, to justify concrete
implementations of code-generation algorithms
in one-level languages, we use a {\em native
embedding} of a two-level language into a
one-level language.\bibpar
We present two-level languages with these
properties both for a call-by-name object
language and for a call-by-value computational
object language. Indeed, it is these properties
call-by-value case. We consider two non-trivial
applications: a one-pass transformation into
continuation-passing style and type-directed
partial evaluation for call-by-name and for
call-by-value",
}

@techreport{BRICS-RS-00-45,
author = 	 "Damg{\aa}rd, Ivan B. and Jurik, Mads J.",
title = 	 "A Generalisation, a Simplification and some
Applications of {P}aillier's Probabilistic
Public-Key System",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-45",
month = 	 dec,
note = 	 "18~pp. Appears in " # lncs1992 # ", pages
119--136. This revised and extended report
supersedes the earlier BRICS report RS-00-5",
abstract = 	 "We propose a generalisation of Paillier's
probabilistic public key system, in which the
expansion factor is reduced and which allows to
adjust the block length of the scheme even
after the public key has been fixed, without
loosing the homomorphic property. We show that
the generalisation is as secure as Paillier's
original system.\bibpar
We construct a threshold variant of the
generalised scheme as well as zero-knowledge
protocols to show that a given ciphertext
encrypts one of a set of given plaintexts, and
protocols to verify multiplicative relations on
plaintexts.\bibpar
We then show how these building blocks can be
used for applying the scheme to efficient
electronic voting. This reduces dramatically
the work needed to compute the final result of
an election, compared to the previously best
known schemes. We show how the basic scheme for
a yes/no vote can be easily adapted to casting
a vote for up to $t$ out of $L$ candidates. The
same basic building blocks can also be adapted
to provide receipt-free elections, under
appropriate physical assumptions. The scheme
for 1 out of $L$ elections can be optimised
such that for a certain range of parameter
values, a ballot has size only $O(\log L)$
bits.",
}

@techreport{BRICS-RS-00-44,
author = 	 "Grobauer, Bernd and Yang, Zhe",
title = 	 "The Second {F}utamura Projection for
Type-Directed Partial Evaluation",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-44",
month = 	 dec,
note = 	 "Appears in {\em Higher-Order and Symbolic
Computation} 14(2--3):173--219 (2001). This
revised and extended report supersedes the
earlier BRICS report RS-99-40 which in turn was
an extended version of " # acmpepm00 # ", pages
22--32",
abstract = 	 "A generating extension of a program
specializes the program with respect to part of
the input. Applying a partial evaluator to the
program trivially yields a generating
extension, but specializing the partial
evaluator with respect to the program often
yields a more efficient one. This
specialization can be carried out by the
partial evaluator itself; in this case, the
process is known as the second Futamura
projection.\bibpar
We derive an ML implementation of the second
Futamura projection for Type-Directed Partial
Evaluation (TDPE). Due to the differences
evaluation and TDPE, this derivation involves
several conceptual and technical steps. These
include a suitable formulation of the second
Futamura projection and techniques for making
TDPE amenable to self-application. In the
context of the second Futamura projection, we
also compare and relate TDPE with conventional
offline partial evaluation.\bibpar
We demonstrate our technique with several
examples, including compiler generation for
Tiny, a prototypical imperative language.",
}
@techreport{BRICS-RS-00-43,
author = 	 "Brabrand, Claus and M{\o}ller, Anders and
Christensen, Mikkel Ricky and Schwartzbach,
Michael I.",
title = 	 "{PowerForms}: Declarative Client-Side Form
Field Validation",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-43",
month = 	 dec,
note = 	 "21~pp. Appears in {\em World Wide Web
Journal}, 4(3), 2000",
abstract = 	 "All uses of HTML forms may benefit from
validation of the specified input field values.
Simple validation matches individual values
against specified formats, while more advanced
validation may involve interdependencies of
form fields.\bibpar
There is currently no standard for specifying
or implementing such validation. Today, CGI
programmers often use Perl libraries for simple
server-side validation or program customized
JavaScript solutions for client-side
validation.\bibpar
We present PowerForms, which is an add-on to
HTML forms that allows a purely declarative
specification of input formats and
sophisticated interdependencies of form fields.
While our work may be seen as inspiration for a
future extension of HTML, it is also available
for CGI programmers today through a
preprocessor that translates a PowerForms
document into a combination of standard HTML
and JavaScript that works on all combinations
of platforms and browsers. \bibpar
The definitions of PowerForms formats are
syntactically disjoint from the form itself,
which allows a modular development where the
form is perhaps automatically generated by
other tools and the formats and
}
@techreport{BRICS-RS-00-42,
author = 	 "Brabrand, Claus and M{\o}ller, Anders and
Schwartzbach, Michael I.",
title = 	 "The {\tt} Project",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-42",
month = 	 dec,
note = 	 "25~pp. To appear in " # toit # ", 2002",
abstract = 	 "We present the results of the {\tt}
project, which aims to design and implement a
high-level domain-specific language for
programming interactive Web services. The World
Wide Web has undergone an extreme development
since its invention ten years ago. A
fundamental aspect is the change from static to
dynamic generation of Web pages. Generating Web
pages dynamically in dialogue with the client
has the advantage of providing up-to-date and
systems for constructing such dynamic Web
services has emerged as a whole new research
area. The {\tt} language is designed by
analyzing its application domain and
identifying fundamental aspects of Web
services. Each aspect is handled by a nearly
independent sublanguage, and the entire
collection is integrated into a common core
language. The {\tt} compiler uses the
available Web technologies as target languages,
making {\tt} available on almost any
combination of browser and server, without
relying on plugins or server modules.",
}
@techreport{BRICS-RS-00-41,
author = 	 "Klarlund, Nils and M{\o}ller, Anders and
Schwartzbach, Michael I.",
title = 	 "The {DSD} Schema Language and its
Applications",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-41",
month = 	 dec,
note = 	 "32~pp. Appears in {\em Automated Software
Engineering}, 9(3):285--319,2002. Shorter
version appears in " # acmfmsp00 # " , pages
101--111",
abstract = 	 "XML (eXtensible Markup Language), a linear
syntax for trees, has gathered a remarkable
amount of interest in industry. The acceptance
of XML opens new venues for the application of
formal methods such as specification of
abstract syntax tree sets and tree
transformations.\bibpar
A user domain may be specified as a set of
trees. For example, XHTML is a user domain
corresponding to the set of XML documents that
make sense as HTML. A notation for defining
such a set of XML trees is called a schema
language. We believe that a useful schema
notation must identify most of the syntactic
requirements that the documents in the user
domain follow; allow efficient parsing; be
readable to the user; allow a declarative
default notation a la CSS; and be modular and
extensible to support evolving classes of XML
documents.\bibpar
In the present paper, we give a tutorial
introduction to the DSD (Document Structure
Description) notation as our bid on how to meet
these requirements. The DSD notation was
inspired by industrial needs, and we show how
DSDs help manage aspects of complex XML
software through a case study about interactive
voice response systems (automated telephone
answering systems, where input is through the
The expressiveness of DSDs goes beyond the DTD
schema concept that is already part of XML. We
advocate the use of nonterminals in a top-down
manner, coupled with boolean logic and regular
expressions to describe how constraints on tree
nodes depend on their context. We also support
a general, declarative mechanism for inserting
default elements and attributes that is
reminiscent of Cascading Style Sheets (CSS), a
way of manipulating formatting instructions in
HTML that is built into all modern browsers.
Finally, we include a simple technique for
evolving DSDs through selective redefinitions.
DSDs are in many ways much more expressive than
XML Schema (the schema language proposed by the
W3C), but their syntactic and semantic
definition in English is only 1/8th the size.
Also, the DSD notation is self-describable: the
syntax of legal DSD documents and all static
semantic requirements can be captured in a DSD
document, called the meta-DSD",
}
@techreport{BRICS-RS-00-40,
author = 	 "Klarlund, Nils and M{\o}ller, Anders and
Schwartzbach, Michael I.",
title = 	 "{MONA} Implementation Secrets",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-40",
month = 	 dec,
note = 	 "19~pp. Appears in {\em International Journal
of Foundations of Computer Science},
13(4):571--586, 2002. Shorter version appears
in " # lncs2088 # ", pages 182--194",
abstract = 	 "The MONA tool provides an implementation of
automaton-based decision procedures for the
logics WS1S and WS2S. It has been used for
numerous applications, and it is remarkably
efficient in practice, even though it faces a
theoretically non-elementary worst-case
complexity. The implementation has matured over
a period of six years. Compared to the first
naive version, the present tool is faster by
several orders of magnitude. This speedup is
obtained from many different contributions
working on all levels of the compilation and
execution of formulas. We present an overview
of MONA and a selection of implementation
secrets'' that have been discovered and
tested over the years, including formula
reductions, DAGification, guided tree automata,
three-valued logic, eager minimization,
BDD-based automata representations, and
cache-conscious data structures. We describe
these techniques and quantify their respective
effects by experimenting with separate versions
of the MONA tool that in turn omit each of
them",
}
@techreport{BRICS-RS-00-39,
author = 	 "M{\o}ller, Anders and Schwartzbach, Michael
I.",
title = 	 "The Pointer Assertion Logic Engine",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-39",
month = 	 dec,
note = 	 "23~pp. Appears in " # acmpldi01 # " pp.
221--231",
abstract = 	 "We present a new framework for verifying
partial specifications of programs in order to
catch type and memory errors and check data
structure invariants. Our technique can verify
a large class of data structures, namely all
those that can be expressed as graph types.
Earlier versions were restricted to simple
special cases such as lists or trees. Even so,
our current implementation is as fast as the
previous specialized tools.\bibpar
Programs are annotated with partial
specifications expressed in Pointer Assertion
Logic, a new notation for expressing properties
of the program store. We work in the logical
tradition by encoding the programs and partial
second-order logic. Validity of these formulas
is checked by the MONA tool, which also can
provide explicit counterexamples to invalid
formulas.\bibpar
Other work with similar goals is based on more
traditional program analyses, such as shape
analysis. That approach requires explicit
introduction of an appropriate operational
semantics along with a proof of correctness
whenever a new data structure is being
considered. In comparison, our approach only
requires the data structure to be abstractly
described in Pointer Assertion Logic",
}
@techreport{BRICS-RS-00-38,
author = 	 "Jeannet, Bertrand",
title = 	 "Dynamic Partitioning in Linear Relation
Analysis: Application to the Verification of
Synchronous Programs",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-38",
month = 	 dec,
note = 	 "44~pp",
keywords = 	 "Abstract Interpretation, Partitioning, Linear
Relation Analysis, Reactive Systems, Program
Verification",
abstract = 	 "Linear relation analysis is an abstract
interpretation technique that computes linear
constraints satisfied by the numerical
variables of a program. We apply it to the
verification of declarative synchronous
programs. In this approach, {\em state
partitioning\/} plays an important role: on one
hand the precision of the results highly
depends on the fineness of the partitioning; on
the other hand, a too much detailed
partitioning may result in an exponential
explosion of the analysis. In this paper we
propose to consider very general partitions of
the state space and to dynamically select a
suitable partitioning according to the property
to be proved. The presented approach is quite
general and can be applied to other abstract
interpretations",
}

@techreport{BRICS-RS-00-37,
author = 	 "Hune, Thomas S. and Larsen, Kim G. and
title = 	 "Guided Synthesis of Control Programs for a
Batch Plant using {\sc{U}ppaal}",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-37",
month = 	 dec,
note = 	 "29~pp. Appears in " # ieeedsvv00 # ", pages
E15--E22 and {\em Nordic Journal of Computing},
8(1):43--64, 2001.",
abstract = 	 "In this paper we address the problem of
scheduling and synthesizing distributed control
programs for a batch production plant. We use a
timed automata model of the batch plant and the
verification tool Uppaal to solve the
scheduling problem.\bibpar
In modeling the plant, we aim at a level of
abstraction which is sufficiently accurate in
order that synthesis of control programs from
generated timed traces is possible.
Consequently, the models quickly become too
detailed and complicated for immediate
automatic synthesis. In fact, only models of
plants producing two batches can be analyzed
directly! To overcome this problem, we present
a general method allowing the user to guide the
model-checker according to heuristically chosen
strategies. The guidance is specified by
augmenting the model with additional guidance
variables and by decorating transitions with
extra guards on these. Applying this method
have made synthesis of control programs
feasible for a plant producing as many as 60
batches.\bibpar
The synthesized control programs have been
executed in a physical plant. Besides proving
useful in validating the plant model and in
finding some modeling errors, we view this
final step as the ultimate litmus test of our
methodology's ability to generate executable
(and executing) code from basic plant models",
}
@techreport{BRICS-RS-00-36,
author = 	 "Pagh, Rasmus",
title = 	 "Dispersing Hash Functions",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-36",
month = 	 dec,
note = 	 "18~pp. Preliminary version appeared in " #
csrandom00 # ", pages 53--67",
abstract = 	 "A new hashing primitive is introduced:
dispersing hash functions. A family of hash
functions $F$ is dispersing if, for any set $S$
of a certain size and random $h\in F$, the
expected value of $|S|-|h[S]|$ is not much
larger than the expectancy if $h$ had been
chosen at random from the set of all
functions.\bibpar
We give tight, up to a logarithmic factor,
upper and lower bounds on the size of
dispersing families. Such families previously
studied, for example universal families, are
significantly larger than the smallest
dispersing families, making them less suitable
for derandomization. We present several
applications of dispersing families to
derandomization (fast element distinctness, set
inclusion, and static dictionary
initialization). Also, a tight relationship
between dispersing families and extractors,
which may be of independent interest, is
exhibited.\bibpar
We also investigate the related issue of
program size for hash func\-tions which are
nearly perfect. In particular, we exhibit a
dramatic increase in program size for hash
functions more dispersing than a random
function",
}

@techreport{BRICS-RS-00-35,
author = 	 "Danvy, Olivier and Nielsen, Lasse R.",
title = 	 "{CPS} Transformation of Beta-Redexes",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-35",
month = 	 dec,
note = 	 "12~pp. Appears in " # acmcw01 # ", pages
35--39",
keywords = 	 "Continuation-passing style (CPS), Plotkin,
Fischer, one-pass CPS transformation, two-level
lambda-calculus, generalized reduction",
abstract = 	 "The extra compaction of Sabry and Felleisen's
transformation is due to making continuations
occur first in CPS terms and classifying more
redexes as administrative. We show that the
extra compaction is actually independent of the
relative positions of values and continuations
and furthermore that it is solely due to a
context-sensitive transformation of
beta-redexes. We stage the more compact CPS
transformation into a first-order uncurrying
phase and a context-insensitive CPS
transformation. We also define a
context-insensitive CPS transformation that is
just as compact. This CPS transformation
operates in one pass and is dependently typed",
}
@techreport{BRICS-RS-00-34,
author = 	 "Danvy, Olivier and Rhiger, Morten",
title = 	 "A Simple Take on Typed Abstract Syntax in
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-34",
month = 	 dec,
note = 	 "25~pp. Appears in " # lncs2024 # ", pages
343--358",
abstract = 	 "We present a simple way to program typed
abstract syntax in a language following a
Hindley-Milner typing discipline, such as ML
and Haskell, and we apply it to automate two
embodied in type-directed partial evaluation
for the simply typed lambda calculus: (1)
normalization functions preserve types and (2)
they yield long beta-eta normal forms",
}
@techreport{BRICS-RS-00-33,
author = 	 "Danvy, Olivier and Nielsen, Lasse R.",
title = 	 "A Higher-Order Colon Translation",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-33",
month = 	 dec,
note = 	 "17~pp. Appears in " # lncs2024 # ", pages
78--91",
abstract = 	 "A lambda-encoding such as the CPS
redexes. In his seminal article Call-by-name,
call-by-value and the lambda-calculus'', 25
reductions using a so-called colon
translation.'' 10 years ago, Danvy and Filinski
integrated administrative reductions in the CPS
transformation, making it operate in one pass.
The technique applies to other lambda-encodings
(e.g., variants of CPS), but we do not see it
translation appears to be favored. Therefore,
in an attempt to link both techniques, we
recast Plotkin's proof of Indifference and
Simulation to the higher-order specification of
the one-pass CPS transformation. To this end,
we extend his colon translation from first
order to higher order",
}
@techreport{BRICS-RS-00-32,
author = 	 "Reynolds, John C.",
title = 	 "The Meaning of Types --- From Intrinsic to
Extrinsic Semantics",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-32",
month = 	 dec,
note = 	 "35~pp. A shorter version of this report
describing a more limited language appears in
Annabelle McIver and Carroll Morgan (eds.) {\em
Essays on Programming Methodology},
Springer-Verlag, New York, 2001",
abstract = 	 "A definition of a typed language is said to be
intrinsic'' if it assigns meanings to typings
rather than arbitrary phrases, so that
ill-typed phrases are meaningless. In contrast,
a definition is said to be extrinsic'' if all
phrases have meanings that are independent of
their typings, while typings represent
properties of these meanings.\bibpar
For a simply typed lambda calculus, extended
with recursion, subtypes, and named products,
we give an intrinsic denotational semantics and
a denotational semantics of the underlying
untyped language. We then establish a logical
relations theorem between these two semantics,
and show that the logical relations can be
bracketed'' by retractions between the
domains of the two semantics. From these
results, we derive an extrinsic semantics that
uses partial equivalence relations",
}
@techreport{BRICS-RS-00-31,
author = 	 "Grobauer, Bernd and Lawall, Julia L.",
title = 	 "Partial Evaluation of Pattern Matching in
Strings, revisited",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-31",
month = 	 nov,
note = 	 "48~pp. Appears in {\em Nordic Journal of
Computing}, 8(4):437--462, 2001",
abstract = 	 "Specializing string matchers is a canonical
example of partial evaluation. A naive
implementation of a string matcher repeatedly
matches a pattern against every substring of
the data string; this operation should
intuitively benefit from specializing the
matcher with respect to the pattern. In
practice, however, producing an efficient
implementation by performing this
specialization using standard
partial-evaluation techniques has been found to
require non-trivial binding-time improvements.
Starting with a naive matcher, we thus present
a derivation of a binding-time improved string
matcher. We prove its correctness and show that
specialization with respect to a pattern yields
a matcher with code size linear in the length
of the pattern and running time linear in the
length of its input. We then consider several
variants of matchers that specialize well,
amongst them the first such matcher presented
in the literature, and we demonstrate how
variants can be derived from each other
systematically",
}
@techreport{BRICS-RS-00-30,
author = 	 "Damg{\aa}rd, Ivan B. and Koprowski, Maciej",
title = 	 "Practical Threshold {RSA} Signatures Without a
Trusted Dealer",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-30",
month = 	 nov,
note = 	 "14~pp. Appears in " # lncs2045 # ", pages
152--165",
abstract = 	 "We propose a threshold RSA scheme which is as
efficient as the fastest previous threshold RSA
scheme (by Shoup), but where two assumptions
needed in Shoup's and in previous schemes can
be dropped, namely that the modulus must be a
product of safe primes and that a trusted
dealer generates the keys",
}
@techreport{BRICS-RS-00-29,
author = 	 "Santocanale, Luigi",
title = 	 "The Alternation Hierarchy for the Theory of
$\mu$-lattices",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-29",
month = 	 nov,
note = 	 "44~pp. Extended abstract appears in {\em
Abstracts from the International Summer
Conference in Category Theory}, CT2000, Como,
Italy, July 16--22, 2000. Appears in {\em
Theory and Applications of Categories},
9:166--197, 2002",
abstract = 	 "The alternation hierarchy problem asks whether
every $\mu$-term, that is a term built up using
also a least fixed point constructor as well as
a greatest fixed point constructor, is
equivalent to a $\mu$-term where the number of
nested fixed point of a different type is
bounded by a fixed number.\bibpar
In this paper we give a proof that the
alternation hierarchy for the theory of $\mu$-lattices is strict, meaning that such number
does not exist if $\mu$-terms are built up from
the basic lattice operations and are
interpreted as expected. The proof relies on
the explicit characterization of free $\mu$-lattices by means of games and strategies",
}
@techreport{BRICS-RS-00-28,
author = 	 "Santocanale, Luigi",
title = 	 "Free $\mu$-lattices",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-28",
month = 	 nov,
note = 	 "51~pp. Short abstract appeared in {\em
Proceedings of Category Theory 99}, Coimbra,
Portugal, July 19--24, 1999. Full version
appears in the Journal of Pure and Applied
Algebra, 168/2-3, pp. 227-264",
abstract = 	 "A $\mu$-lattice is a lattice with the property
that every unary polynomial has both a least
and a greatest fix-point. In this paper we
define the quasivariety of $\mu$-lattices and,
for a given partially ordered set $P$, we
construct a $\mu$-lattice ${\cal J}_{P}$ whose
elements are equivalence classes of games in a
preordered class ${\cal J}(P)$. We prove that
the $\mu$-lattice ${\cal J}_{P}$ is free over
the ordered set $P$ and that the order relation
of $\mathcal{J}_{P}$ is decidable if the order
relation of $P$ is decidable. By means of this
characterization of free $\mu$-lattices we
infer that the class of complete lattices
generates the quasivariety of $\mu$-lattices",
}
@techreport{BRICS-RS-00-27,
author = 	 "{\'E}sik, Zolt{\'a}n and Kuich, Werner",
title = 	 "Inductive $^*$-Semirings",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-27",
month = 	 oct,
note = 	 "34~pp. To appear in {\em Theoretical Computer
Science}",
abstract = 	 "One of the most well-known induction
principles in computer science is the fixed
point induction rule, or least pre-fixed point
rule. Inductive $^*$-semirings are partially
ordered semirings equipped with a star
operation satisfying the fixed point equation
and the fixed point induction rule for linear
terms. Inductive $^*$-semirings are extensions
of continuous semirings and the Kleene algebras
of Conway and Kozen.\bibpar
We develop, in a systematic way, the rudiments
of the theory of inductive $^*$-semirings in
relation to automata, languages and power
series. In particular, we prove that if $S$ is
an inductive $^*$-semiring, then so is the
semiring of matrices $S^{n \times n}$, for any
integer $n \geq 0$, and that if $S$ is an
inductive $^*$-semiring, then so is any
semiring of power series $S\langle\kern-.5em \langle A^* \rangle\kern-.5em \rangle$. As
shown by Kozen, the dual of an inductive
$^*$-semiring may not be inductive. In
contrast, we show that the dual of an iteration
semiring is an iteration semiring. Kuich proved
a general Kleene theorem for continuous
semirings, and Bloom and {\'E}sik proved a
Kleene theorem for all Conway semirings. Since
any inductive $^*$-semiring is a Conway
semiring and an iteration semiring, as we show,
there results a Kleene theorem applicable to
all inductive $^*$-semirings. We also describe
the structure of the initial inductive
$^*$-semiring and conjecture that any free
inductive $^*$-semiring may be given as a
semiring of rational power series with
coefficients in the initial inductive
$^*$-semiring. We relate this conjecture to
recent axiomatization results on the equational
theory of the regular sets",
}
@techreport{BRICS-RS-00-26,
author = 	 "{\v C}apkovi{\v c}, Franti{\v s}ek",
title = 	 "Modelling and Control of Discrete Event
Dynamic Systems",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-26",
month = 	 oct,
note = 	 "58~pp",
abstract = 	 "Discrete event dynamic systems (DEDS) in
general are investigated as to their analytical
models most suitable for control purposes and
as to the analytical methods of the control
synthesis. The possibility of utilising both
the selected kind of Petri nets and the
oriented graphs on this way is pointed out.
Because many times the control task
specifications (like criteria, constraints,
special demands, etc.) are given only verbally
or in another form of non analytical terms, a
specifications is needed. Special kinds of
Petri nets (logical, fuzzy) are suitable on
this way too. Hence, the knowledge-based
control synthesis of DEDS can also be examined.
The developed graphical tools for model drawing
and testing as well as for the automated
knowledge-based control synthesis are described
and illustratively presented.\bibpar
Two approaches to modelling and control
synthesis based on oriented graphs are
developed. They are suitable when the system
model is described by the special kind of Petri
nets - state machines. At the control synthesis
the first of them is straightforward while the
second one combines both the straight-lined
model dynamics development (starting from the
given initial state towards the prescribed
terminal one) and the backtracking model
dynamics development. ",
}

@techreport{BRICS-RS-00-25,
author = 	 "{\'E}sik, Zolt{\'a}n",
title = 	 "Continuous Additive Algebras and Injective
Simulations of Synchronization Trees",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-25",
address = 	 iesd # " and Department of Computer Science,
University of Szeged, Hungary",
month = 	 sep,
note = 	 "41~pp. Appears in {\em Journal of Logic and
Computation}, 12(2):271--300, 2002",
abstract = 	 "The (in)equational properties of the least
fixed point operation on ($\omega$-)contin\-uous functions on ($\omega$-)complete partially ordered sets are captured
by the axioms of (ordered) iteration algebras,
or iteration theories. We show that the
inequational laws of the sum operation in
conjunction with the least fixed point
operation in continuous additive algebras have
a finite axiomatization over the inequations of
ordered iteration algebras. As a byproduct of
this relative axiomatizability result, we
obtain complete infinite inequational and
finite implicational axiomatizations. Along the
way of proving these results, we give a
concrete description of the free algebras in
the corresponding variety of ordered iteration
algebras. This description uses injective
simulations of regular synchronization trees.
Thus, our axioms are also sound and complete
for the injective simulation (resource bounded
simulation) of (regular) processes",
}
@techreport{BRICS-RS-00-24,
author = 	 "Brabrand, Claus and Schwartzbach, Michael I.",
title = 	 "Growing Languages with Metamorphic Syntax
Macros",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-24",
month = 	 sep,
note = 	 "22~pp. Appears in " # acmpepm02 # ", pages
31--40",
abstract = 	 "{\emFrom now on, a main goal in designing a
language should be to plan for growth.'' Guy
Steele: Growing a Language, OOPSLA'98 invited
talk.}\bibpar

We present our experiences with a syntax macro
language augmented with a concept of {\em
metamorphisms}. We claim this forms a general
abstraction mechanism for growing
(domain-specific) extensions of programming
languages.\bibpar

Our syntax macros are similar to previous work
in that the compiler accepts collections of
grammatical rules that extend the syntax in
which a subsequent program may be written. We
exhibit how almost arbitrary extensions can be
defined in a purely {\em declarative\/} manner
without resorting to compile-time programming.
The macros are thus {\em terminating\/} in that
parsing is guaranteed to terminate, {\em
hygienic\/} since full $\alpha$-conversion
eliminates the risk of name clashes, and {\em
transparent\/} such that subsequent phases in
the compiler are unaware of them. Error
messages from later phases in the compiler are
tracked through all macro invocations to
pinpoint their sources in the extended
syntax.\bibpar

A concept of {\em metamorphic rules\/} allows
the arguments of a macro to be defined in an
almost arbitrary {\em meta\/} level grammar and
then to be {\em morphed\/} into the host
language.\bibpar

We show through examples how creative use of
metamorphic syntax macros may be used not only
to create convenient shorthand notation but
also to introduce new language concepts and
mechanisms. In fact, whole new languages can be
created at surprisingly low cost. The resulting
programs are significantly easier to understand
and maintain.\bibpar

This work is fully implemented as part of the
$<$bigwig$>$ system for defining interactive
Web services, but could find use in many other
languages",
}
@techreport{BRICS-RS-00-23,
author = 	 "Aceto, Luca and Ing{\'o}lfsd{\'o}ttir, Anna
and Pedersen, Mikkel Lykke and Poulsen, Jan",
title = 	 "Characteristic Formulae for Timed Automata",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-23",
month = 	 sep,
note = 	 "23~pp. Appears in {\em RAIRO, Theoretical
Informatics and Applications} 34(6), pp.
565--584.",
abstract = 	 "This paper offers characteristic formula
constructions in the real-time logic $L_{\nu}$
for several behavioural relations between
(states of) timed automata. The behavioural
relations studied in this work are timed
faster-than bisimilarity and timed trace
inclusion. The characteristic formulae
delivered by our constructions have size which
is linear in that of the timed automaton they
logically describe. This also applies to the
characteristic formula for timed bisimulation
equivalence, for which an exponential space
construction was previously offered by
Laroussinie, Larsen and Weise",
}
@techreport{BRICS-RS-00-22,
author = 	 "Hune, Thomas S. and Sandholm, Anders B.",
title = 	 "Using Automata in Control Synthesis --- {A}
Case Study",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-22",
month = 	 sep,
note = 	 "20~pp. Appears in " # lncs1783 # ", pages
349--362",
abstract = 	 "We study a method for synthesizing control
programs. The method merges an existing control
program with a control automaton. For
specifying the control automata we have used
monadic second order logic over strings. Using
the Mona tool, specifications are translated
into automata. This yields a new control
program restricting the behavior of the old
control program such that the specifications
are satisfied. The method is presented through
a concrete example",
}

@techreport{BRICS-RS-00-21,
author = 	 "M{\"o}ller, M. Oliver and Alur, Rajeev",
title = 	 "Heuristics for Hierarchical Partitioning with
Application to Model Checking",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-21",
month = 	 aug,
note = 	 "30~pp. A shorter version appears in " #
lncs2144 # ", pages 71--85",
abstract = 	 "Given a collection of connected components, it
is often desired to cluster together parts of
strong correspondence, yielding a hierarchical
structure. We address the automation of this
process and apply heuristics to battle the
combinatorial and computational complexity. We
define a cost function that captures the
quality of a structure relative to the
connections and favors shallow structures with
a low degree of branching. Finding a structure
with minimal cost is shown to be $NP$-complete.
We present a greedy polynomial-time algorithm
that creates an approximative good solution
incrementally by local evaluation of a
heuristic function. We compare some simple
heuristic functions and argue for one based on
four criteria: The number of enclosed
connections, the number of components, the
number of touched connections and the depth of
the structure. We report on an application in
the context of formal verification, where our
algorithm serves as a preprocessor for a
temporal scaling technique, called {\emNext''
heuristic}. The latter is applicable in
enumerative reachability analysis and is
Mocha} model checking tool. We demonstrate
performance and benefits of our method and use
an asynchronous parity computer, a standard
leader election algorithm, and an opinion poll
protocol as case studies",
}
@techreport{BRICS-RS-00-20,
author = 	 "Aceto, Luca and Fokkink, Willem Jan and
Ing{\'o}lfsd{\'o}ttir, Anna",
title = 	 "2-Nested Simulation is not Finitely
Equationally Axiomatizable",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-20",
month = 	 aug,
note = 	 "13~pp. Appears in " # lncs2010 # ", pages
39--50",
abstract = 	 "2-nested simulation was introduced by Groote
and Vaandrager as the coarsest equivalence
included in completed trace equivalence for
which the tyft/tyxt format is a congruence
format. In the linear time-branching time
spectrum of van Glabbeek, 2-nested simulation
is one of the few equivalences for which no
finite equational axiomatization is presented.
In this paper we prove that such an
axiomatization does not exist for 2-nested
simulation",
}
@techreport{BRICS-RS-00-19,
author = 	 "Variyam, Vinodchandran N.",
title = 	 "A Note on {${\bf NP}\cap{\bf coNP}{\rm /poly}$}",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-19",
month = 	 aug,
note = 	 "7~pp",
abstract = 	 "In this note we show that ${\bf AM}_{\small\bf exp} \not\subseteq{\bf NP}\cap{\bf coNP}{\rm /poly}$, where ${\bf AM}_{\small\bf exp}$
denotes the exponential version of the class
${\bf AM}$. The main part of the proof is a
collapse of ${\bf EXP}$ to ${\bf AM}$ under the
assumption that ${\bf EXP}\subseteq{\bf NP}\cap {\bf coNP}{\rm/poly}$",
}
@techreport{BRICS-RS-00-18,
author = 	 "Crazzolara, Federico and Winskel, Glynn",
title = 	 "Language, Semantics, and Methods for
Cryptographic Protocols",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-18",
month = 	 aug,
note = 	 "ii+42~pp",
abstract = 	 "In this report we present a process language
for security protocols together with an
operational semantics and an alternative
semantics in terms of sets of events. The
denotation of process is a set of events, and
as each event specifies a set of pre and
postconditions, this denotation can be viewed
as a Petri net. This Petri-net semantics has a
strong relation to both Paulson's inductive set
of rules and the strand space approach. By
means of an example we illustrate how the
Petri-net semantics can be used to prove
properties such as secrecy and authentication",
}

@techreport{BRICS-RS-00-17,
author = 	 "Hune, Thomas S.",
title = 	 "Modeling a Language for Embedded Systems in
Timed Automata",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-17",
month = 	 aug,
note = 	 "26~pp. Earlier version entitled {\em Modelling
a Real-Time Language} appeared in " # fmics99 #
", pages 259--282",
abstract = 	 "We present a compositional method for
translating real-time programs into networks of
timed automata. Programs are written in an
assembly like real-time language and translated
into models supported by the tool Uppaal. We
have implemented the translation and give an
example of its application on a simple control
program for a car. Some properties of the
behavior of the control program are verified
using the generated model",
}

@techreport{BRICS-RS-00-16,
author = 	 "Srba, Ji{\v r}{\'\i}",
title = 	 "Complexity of Weak Bisimilarity and Regularity
for {BPA} and {BPP}",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-16",
month = 	 jun,
note = 	 "20~pp. To appear in " # entcsexpress00,
abstract = 	 "It is an open problem whether weak
bisimilarity is decidable for Basic Process
Algebra (BPA) and Basic Parallel Processes
(BPP). A PSPACE lower bound for BPA and NP
lower bound for BPP have been demonstrated by
Stribrna. Mayr achieved recently a result,
saying that weak bisimilarity for BPP is $\Pi_2 ^P$-hard. We improve this lower bound to
PSPACE, moreover for the restricted class of
normed BPP.\bibpar
Weak regularity (finiteness) of BPA and BPP is
not known to be decidable either. In the case
of BPP there is a $\Pi_2^P$-hardness result by
Mayr, which we improve to PSPACE. No lower
bound has previously been established for BPA.
We demonstrate DP-hardness, which in particular
implies both NP and co-NP-hardness.\bibpar
In each of the bisimulation/regularity problems
we consider also the classes of normed
processes",
}

@techreport{BRICS-RS-00-15,
author = 	 "Damian, Daniel and Danvy, Olivier",
title = 	 "Syntactic Accidents in Program Analysis: On
the Impact of the {CPS} Transformation",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-15",
month = 	 jun,
note = 	 "26~pp. Extended version of an article
appearing in " # acmicfp00 # ", pages 209--220.
To appear in {\em Journal of Functional
Programming}.",
abstract = 	 "We show that a non-duplicating CPS
transformation has no effect on control-flow
analysis and that it has a positive effect on
binding-time analysis: a monovariant
control-flow analysis yields strictly
comparable results on a direct-style program
and on its CPS counterpart; and a monovariant
binding-time analysis yields more precise
results on a CPS program than on its
direct-style counterpart. Our proof technique
amounts to constructing the
continuation-passing style (CPS) counterpart of
flow information and of binding times.\bibpar
Our results confirm a common intuition about
control-flow analysis, namely that it is
orthogonal to the CPS transformation. They also
prove a folklore theorem about binding-time
analysis, namely that CPS has a positive impact
on binding times. What may be more surprising
is that this beneficial effect holds even if
contexts or continuations are not
duplicated.\bibpar
The present study is symptomatic of an
unsettling property of program analyses: their
quality is unpredictably vulnerable to
syntactic accidents in source programs, i.e.,
to the way these programs are written. More
reliable program analyses require a better
understanding of the effects of syntactic
change. ",
}
@techreport{BRICS-RS-00-14,
author = 	 "Cramer, Ronald and Damg{\aa}rd, Ivan B. and
Nielsen, Jesper Buus",
title = 	 "Multiparty Computation from Threshold
Homomorphic Encryption",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-14",
month = 	 jun,
note = 	 "ii+38~pp. Appears in " # lncs2045 # ", pages
280--300",
abstract = 	 "We introduce a new approach to multiparty
computation (MPC) basing it on homomorphic
threshold crypto-systems. We show that given
keys for any sufficiently efficient system of
this type, general MPC protocols for $n$
players can be devised which are secure against
an active adversary that corrupts any minority
of the players. The total number of bits sent
is $O(nk|C|)$, where $k$ is the security
parameter and $|C|$ is the size of a (Boolean)
circuit computing the function to be securely
evaluated. An earlier proposal by Franklin and
Haber with the same complexity was only secure
for passive adversaries, while all earlier
protocols with active security had complexity
at least quadratic in $n$. We give two examples
of threshold cryptosystems that can support our
construction and lead to the claimed
complexities.",
}
@techreport{BRICS-RS-00-13,
author = 	 "Kl{\'\i}ma, Ond{\v r}ej and Srba,
Ji{\v r}{\'\i}",
title = 	 "Matching Modulo Associativity and Idempotency
is {NP}-Complete",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-13",
month = 	 jun,
note = 	 "19~pp. Appeared in " # lncs1893 # ", pages
456--466",
abstract = 	 "We show that AI-matching (AI denotes the
theory of an associative and idempotent
function symbol), which is solving matching
word equations in free idempotent semigroups,
is NP-complete.",
}
@techreport{BRICS-RS-00-12,
author = 	 "Kohlenbach, Ulrich",
title = 	 "Intuitionistic Choice and Restricted Classical
Logic",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-12",
month = 	 may,
note = 	 "9~pp. Appears in {\em Mathematical Logic
Quaterly} vol 47, pp. 455-460, 2001,",
abstract = 	 "Recently, Coquand and Palmgren considered
systems of intuitionistic arithmetic in all
finite types together with various forms of the
axiom of choice and a numerical omniscience
schema ({\bf NOS}) which implies classical
logic for arithmetical formulas. Feferman
subsequently observed that the proof theoretic
strength of such systems can be determined by
functional interpretation based on a
non-constructive $\mu$-operator and his
well-known results on the strength of this
operator from the 70's. \\
In this note we consider a weaker form {\bf
LNOS} (lesser numerical omniscience schema) of
{\bf NOS} which suffices to derive the strong
form of binary K{\"o}nig's lemma studied by
Coquand/Palmgren and gives rise to a new and
mathematically strong semi-classical system
which, nevertheless, can proof theoretically be
reduced to primitive recursive arithmetic {\bf
PRA}. The proof of this fact relies on
functional interpretation and a majorization
technique developed in a previous paper.",
}
@techreport{BRICS-RS-00-11,
author = 	 "Pagter, Jakob",
title = 	 "On {A}jtai's Lower Bound Technique for $R$-way
Branching Programs and the {H}amming Distance
Problem",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-11",
month = 	 may,
note = 	 "18~pp",
abstract = 	 "In this report we study the proof employed by
Miklos Ajtai [{\em Determinism versus
Non-Determinism for Linear Time RAMs with
Memory Restrictions}, 31st Symposium on Theory
of Computation (STOC), 1999] when proving a
non-trivial lower bound in a general model of
computation for the Hamming distance problem:
given $n$ elements decide whether any two of
them have small'' Hamming distance.
Specifically, Ajtai was able to show that any
$R$-way branching program deciding this problem
using time $O(n)$ must use space $\Omega(n\lg n)$. We generalize Ajtai's original proof
allowing us to prove a time-space trade-off for
deciding the Hamming distance problem in the
$R$-way branching program model for time
between $n$ and $\alpha n\lg n$, for some
suitable $0<\alpha<1$. In particular we prove
that if space is \smash{$O(n^{1-\epsilon})$},
then time is $\Omega(n\lg n)$",
}

@techreport{BRICS-RS-00-10,
author = 	 "Dantchev, Stefan and Riis, S{\o}ren",
title = 	 "A Tough Nut for Tree Resolution",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-10",
month = 	 may,
note = 	 "13~pp",
abstract = 	 "One of the earliest proposed hard problems for
theorem provers is a propositional version of
the {\em Mutilated Chessboard} {\em problem}.
It is well known from recreational mathematics:
Given a chessboard having two diagonally
opposite squares removed, prove that it cannot
be covered with dominoes. In Proof Complexity,
we consider not ordinary, but $2n\times 2n$
mutilated chessboard. In the paper, we show a
$2^{\Omega\left( n\right) }$ lower bound for
{\em tree resolution.} ",
}

@techreport{BRICS-RS-00-9,
author = 	 "Kohlenbach, Ulrich",
title = 	 "Effective Uniform Bounds on the
{K}rasnoselski-{M}ann Iteration",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-9",
month = 	 may,
note = 	 "34~pp. The material of this report appeared as
two publications: 1) A Quantitative version of
a theorem due to Borwein-Reich-Shafrir,
Numer.Funct. Aanal.Optimiz. 22, pp. 641-656
(2001), 2) On the computational content of the
Krasnoselski and Ishikawa fixed point theorems.
In Blanck (et.al.) eds., CCA 2000, LNCS 2064,
pp. 119-145 (2001).",
abstract = 	 "This paper is a case study in proof mining
applied to non-effective proofs in nonlinear
functional anlysis. More specifically, we are
concerned with the fixed point theory of
nonexpansive selfmappings $f$ of convex sets
$C$ in normed spaces. We study the Krasnoselski
iteration as well as more general so-called
Krasnoselski-Mann iterations. These iterations
converge to fixed points of $f$ only under
special compactness conditions and even for
uniformly convex spaces the rate of convergence
is in general not computable in $f$ (which is
related to the non-uniqueness of fixed points).
However, the iterations yield approximate fixed
points of arbitrary quality for general normed
spaces and bounded $C$ (asymptotic
regularity).\bibpar
In this paper we apply general proof theoretic
results obtained in previous papers to
non-effective proofs of this regularity and
extract uniform explicit bounds on the rate of
the asymptotic regularity. We start off with
the classical case of uniformly convex spaces
treated already by Krasnoselski and show how a
logically motivated modification allows to
obtain an improved bound. Already the analysis
of the original proof (from 1955) yields an
elementary proof for a result which was
obtained only in 1990 with the use of the deep
Browder-G{\"o}hde-Kirk fixed point theorem. The
improved bound from the modified proof gives
applied to various special spaces results which
calculations and which in some case are known
to be optimal.\bibpar
The main section of the paper deals with the
general case of arbitrary normed spaces and
yields new results including a quantitative
analysis of a theorem due to Borwein, Reich and
Shafrir (1992) on the asymptotic behaviour of
the general Krasnoselski-Mann iteration in
arbitrary normed spaces even for unbounded sets
$C$. Besides providing explicit bounds we also
get new qualitative results concerning the
independence of the rate of convergence of the
norm of that iteration from various input data.
In the special case of bounded convex sets,
where by well-known results of Ishikawa,
Edelstein/O'Brian and Goebel/Kirk the norm of
the iteration converges to zero, we obtain
uniform bounds which do not depend on the
starting point of the iteration and the
nonexpansive function and the normed space $X$
and, in fact, only depend on the error
$\varepsilon$, an upper bound on the diameter
of $C$ and some very general information on the
sequence of scalars $\lambda_k$ used in the
iteration. Even non-effectively only the
existence of bounds satisfying weaker
uniformity conditions was known before except
for the special situation, where $\lambda_k :=\lambda$ is constant. For the unbounded case,
no quantitative information was known so far.",
}
@techreport{BRICS-RS-00-8,
author = 	 "Mustafa, Nabil H. and Peke{\v c}, Aleksandar",
title = 	 "Democratic Consensus and the Local Majority
Rule",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-8",
month = 	 may,
note = 	 "38~pp",
abstract = 	 "In this paper we study a rather generic
communication/coordination/computation problem:
in a finite network of agents, each initially
having one of the two possible states, can the
majority initial state be computed and agreed
upon (i.e., can a democratic consensus be
reached) by means of iterative application of
the local majority rule. We show that this task
is failure-free only in the networks that are
nowhere truly local. In other words, the idea
of solving a truly global task (reaching
consensus on majority) by means of truly local
computation only (local majority rule) is
doomed for failure.\bibpar
We also show that even well connected networks
of agents that are nowhere truly local might
fail to reach democratic consensus when the
local majority rule is applied iteratively.
Structural properties of democratic consensus
computers, i.e., the networks in which
iterative application of the local majority
rule always yields consensus in the initial
majority state, are presented.",
}

@techreport{BRICS-RS-00-7,
author = 	 "Arge, Lars and Pagter, Jakob",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-7",
month = 	 apr,
note = 	 "Appears in " # lncs1851 # ", pages 448--461",
abstract = 	 "We define external memory (or I/O) models
which capture space complexity and develop a
general technique for deriving I/O-space
trade-offs in these models from internal memory
technique we show strong I/O-space product
lower bounds for Sorting and Element
Distinctness. We also develop new space
efficient external memory Sorting algorithms",
}

@techreport{BRICS-RS-00-6,
author = 	 "Damg{\aa}rd, Ivan B. and Nielsen, Jesper
Buus",
title = 	 "Improved Non-Committing Encryption Schemes
based on a General Complexity Assumption",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-6",
month = 	 mar,
note = 	 "24~pp. Appears in " # lncs1880 # ", pages
433--451",
abstract = 	 "Non-committing encryption enables the
construction of multiparty computation
protocols secure against an {\em adaptive}
adversary in the computational setting where
private channels between players are not
assumed. While any non-committing encryption
scheme must be secure in the ordinary semantic
sense, the converse is not necessarily true. We
propose a construction of non-committing
encryption that can be based on any public key
system which is secure in the ordinary sense
and which has an extra property we call {\em
simulatability}. The construction contains an
earlier proposed scheme by Beaver based on the
Diffie-Hellman problem as a special case, and
we propose another implementation based on RSA.
In a more general setting, our construction can
be based on any collection of trapdoor one-way
permutations with a certain simulatability
property. This offers a considerable efficiency
improvement over the first non-committing
encryption scheme proposed by Canetti et al.
Finally, at some loss of efficiency, our scheme
can be based on general collections of trapdoor
one-way permutations without the simulatability
assumption, and without the common domain
assumption of Canetti et al. ",
}
@techreport{BRICS-RS-00-5,
author = 	 "Damg{\aa}rd, Ivan B. and Jurik, Mads J.",
title = 	 "Efficient Protocols based on Probabilistic
Encryption using Composite Degree Residue
Classes",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-5",
month = 	 mar,
note = 	 "19~pp",
abstract = 	 "We study various applications and variants of
Paillier's probabilistic encryption scheme.
First, we propose a threshold variant of the
scheme, and also zero-knowledge protocols for
proving that a given ciphertext encodes a given
plaintext, and for verifying multiplication of
encrypted values.\bibpar
We then show how these building blocks can be
used for applying the scheme to efficient
electronic voting. This reduces dramatically
the work needed to compute the final result of
an election, compared to the previously best
known schemes. We show how the basic scheme for
a yes/no vote can be easily adapted to casting
a vote for up to $t$ out of $L$ candidates. The
same basic building blocks can also be adapted
to provide receipt-free elections, under
appropriate physical assumptions. The scheme
for 1 out of $L$ elections can be optimised
such that for a certain range of parameter
values, a ballot has size only $O(\log L)$
bits.\bibpar
Finally, we propose a variant of the encryption
scheme, that allows reducing the expansion
factor of Paillier's scheme from 2 to almost
1.",
}

@techreport{BRICS-RS-00-4,
author = 	 "Pagh, Rasmus",
title = 	 "A New Trade-off for Deterministic
Dictionaries",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-4",
month = 	 feb,
note = 	 "Appears in " # lncs1851 # ", pages 22--31.
Journal version in {\em Nordic Journal of
Computing} 7(3):151--163, 2000 with the title
{\em A Trade-Off for Worst-Case Efficient
Dictionaries}",
abstract = 	 "We consider dictionaries over the universe
$U=\{0,1\}^w$ on a unit-cost RAM with word size
$w$ and a standard instruction set. We present
a linear space deterministic dictionary with
membership queries in time $(\log\log n)^{O(1)}$ and updates in time $(\log n)^{O(1)}$, where $n$ is the size of the set
stored. This is the first such data structure
to simultaneously achieve query time $(\log n)^{o(1)}$ and update time $O(2^{\sqrt{\log n}})$",
}
@techreport{BRICS-RS-00-3,
Wang",
title = 	 "On Memory-Block Traversal Problems in Model
Checking Timed Systems",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-3",
month = 	 jan,
note = 	 "15~pp. Appears in " # lncs1785 # ", pages
127--141",
abstract = 	 "A major problem in model-checking timed
systems is the huge memory requirement. In this
paper, we study the memory-block traversal
problems of using standard operating systems in
exploring the state-space of timed automata. We
report a case study which demonstrates that
deallocating memory blocks (i.e. memory-block
traversal) using standard memory management
routines is extremely time-consuming. The
phenomenon is demonstrated in a number of
experiments by installing the UPPAAL tool on
Windows95, SunOS 5 and Linux. It seems that the
problem should be solved by implementing a
memory manager for the model-checker, which is
a troublesome task as it is involved in the
underlining hardware and operating system. We
present an alternative technique that allows
the model-checker to control the memory-block
traversal strategies of the operating systems
without implementing an independent memory
manager. The technique is implemented in the
UPPAAL model-checker. Our experiments
demonstrate that it results in significant
improvement on the performance of UPPAAL. For
example, it reduces the memory deallocation
time in checking a start-up synchronisation
protocol on Linux from 7 days to about 1 hour.
We show that the technique can also be applied
in speeding up re-traversals of explored
state-space",
}

@techreport{BRICS-RS-00-2,
author = 	 "Walukiewicz, Igor",
title = 	 "Local Logics for Traces",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-2",
month = 	 jan,
note = 	 "30~pp. To appear in {\em Journal of Automata,
Languages and Combinatorics}",
abstract = 	 "A mu-calculus over dependence graph
representation of traces is considered. It is
shown that the mu-calculus cannot express all
monadic second order (MSO) properties of
dependence graphs. Several extensions of the
mu-calculus are presented and it is proved that
these extensions are equivalent in expressive
power to MSO logic. The satisfiability problem
for these extensions is PSPACE complete",
}
@techreport{BRICS-RS-00-1,
author = 	 "Lyngs{\o}, Rune B. and Pedersen, Christian N.
S.",
title = 	 "Pseudoknots in {RNA} Secondary Structures",
institution =  brics,
year = 	 2000,
type = 	 rs,
number = 	 "RS-00-1",
month = 	 jan,
note = 	 "15~pp. Appears in " # acmrecomb00 # ",
201--209 and in {\em Journal of Computational
Biology}, 7(3/4):409--427, 2000",
abstract = 	 "RNA molecules are sequences of nucleotides
that serve as more than mere intermediaries
between DNA and proteins, e.g.\ as catalytic
molecules. Computational prediction of RNA
secondary structure is among the few structure
prediction problems that can be solved
satisfactory in polynomial time. Most work has
been done to predict structures that do not
contain pseudoknots. Allowing pseudoknots
introduce modelling and computational problems.
In this paper we consider the problem of
predicting RNA secondary structure when certain
types of pseudoknots are allowed. We first
present an algorithm that in time $O(n^5)$ and
space $O(n^3)$ predicts the secondary structure
of an RNA sequence of length~$n$ in a model
that allows certain kinds of pseudoknots. We
then prove that the general problem of
predicting RNA secondary structure containing
pseudoknots is {\bf NP}-complete for a large
class of reasonable models of pseudoknots.",
`