MATCH Advanced Summer Schools (LAST ANNOUNCEMENT)

Gabriele Kotsis
Tue, 30 Jun 1998 10:37:11 +0200

Bitte, auch/insbesonders an interessierte Studierende weiterleiten!

Last announcement (Application: before July 1st, 1998)

                      * MATCH ADVANCED SUMMER SCHOOLS *

|                                                                      |
| Performance Models for Discrete Event Systems with Synchronizations: |
|                Formalisms and Analysis Techniques.                   |
|                                                                      |
|                 September 3-11, 1998. Jaca, Spain                    |

|                                                                      |
|           System Engineering. A Petri Net Based Approach             |
|           to Modelling, Verification and Implementation.             |
|                                                                      |
|                 September 14-22, 1998. Jaca, Spain                   |

           All the details can be found on the Schools www page




MATCH (Modelling and Analysis of Time Constrained and
Hierarchical Systems) is a Human Capital and Mobility
initiative, sponsored by the European Union. One of its
objectives is the organisation of two open
complementary Advanced Schools concerning Discrete
Event Dynamic Systems (DEDS), focusing one on
performance modelling and evaluation, and the other on
modelling and verification. Each school can be attended

The intended audience consists of people interested in
both the theoretical and practical aspects of modelling
for evaluation and verification of DEDS. Concepts,
methods and computer supported tools will allow us to
provide answers to questions like the following:

   o Could a token-ring protocol lose or duplicate some
   o How to increase the throughput of a large
     insurance company by a work flow analysis?
   o Is it possible to check whether a flexible
     manufacturing system may have some of its robots
   o How should a production line be designed in order
     to achieve a given production rate?
   o What should be the size of the buffers of ATM
     switches so that the cell loss probability remains
     below a given value?
   o Do the verification and the performance evaluation
     need completely different formalisms?
   o What kind of approaches are available to deal with
     large size and complex DEDS?



Both Advanced Schools will take place at the Residence
of the University of Zaragoza in Jaca (in the Pyrenees
mountains), where International Summer Courses are
being organised since the beginning of this century
---mostly on humanistic studies. Participation is
limited to 40 students per School.

The registration fee and full board lodging is:

   o 100.000 pesetas for one school (10 days) and
   o 170.000 pesetas for both schools (20 days).

A small number of grants will be available. Those
wishing to apply for a grant should send a letter of
explanation, a curriculum vitae and a letter of
recommendation from a major advisor before June 1st,

Participants in each school will receive copies of the
lecture transparencies and the draft of a book covering
the topics of the corresponding school in detail. Full
lodging will be provided (in double rooms) at the
Residence, where all the classes will also take place.
A transport service Zaragoza-Jaca and return will also
be provided. Interesting cultural and sightseeing
excursions are planned.

Laboratories will be organized throughout the schools
to provide the students with practical experience on
the application of the formalisms to concrete examples
and case studies. Several computer tools will be


    Performance Models for Discrete Event Systems with
         Synchronizations: Formalisms and Analysis

            September 3-11, 1998. Jaca, Spain.

                   Scientific Directors:
                  G. Balbo and M. Silva


Aims and Scope

Discrete Event Dynamic Systems (DEDS) are based on a view of
dynamic systems where discrete states and events play a
fundamental role. DEDS are becoming increasingly interesting
as the importance of automation and control grows in modern
technology. Application domains like manufacturing,
transport or telecommunication use extensively concepts and
techniques from DEDS. Design optimization, scheduling
(performance control), monitoring, implementation (possibly
fault-tolerant),... are among the critical issues that
require the use of modelling and of qualitative and
quantitative analysis techniques.

Formal methods for the specification, verification and
performance evaluation of DEDS are becoming more and more
important as systems increase in size and complexity. The
aim of this Advanced School is to present a comprehensive
Petri Net-based framework to model and analyze the
performance of complex distributed systems in which the
interplay of concurrency and cooperation among agents is
crucial at the global system level and in which queueing,
service, routing, and synchronization (e.g. rendez-vous,
capacity constraints,...) are equally important. Other
formalisms, like Queueing Networks and Stochastic Process
Algebras, will be also considered and discussed from the
point of view of their relations with Stochastic Petri Nets.
The interleaving of qualitative and quantitative analysis of
complex DEDS will be stressed.

The most important aspects of net based performance
modelling and analysis techniques will be presented to train
the participants in the effective use of formal models in
existing and possible future application domains.


Intended Audience

People interested in performance evaluation of DEDS
through modelling. The material and the lectures of the
school will be organized in such a way that the
following two, complementary, type of audience can
profit from the school:

   o people with a background in performance evaluation
     willing to deepen their knowledge on performance
     modelling through a Petri net based approach to the
   o people with a background in untimed Petri Net
     theory (or alternative formalisms, like Process
     Algebras) willing to explore the use of the
     formalism for performance evaluation.

Special introductory lectures will be given to provide a
common basic background for all the participants.


Topics and Lecturers

  1. Formalisms (Queueing Networks, Untimed Petri Nets,
     Stochastic Petri Nets, Untimed and Stochastic Process
  2. Modelling techniques and methods: (running) examples
     and case studies.
  3. Properties and Qualitative Analysis (basic logical
     properties, Place-Transition and Colored net
     correctness analysis, performance indices and
     qualitative properties);
  4. Discrete-Event Simulation (centralized schemas,
     synchronous and asynchronous parallel/distributed
  5. Markov Chain Generation (bounded Markovian models,
     one-place unbounded Markovian models, non-Markovian
  6. Net-driven Markov Chain generation (decomposition and
     tensor algebra approach, symmetries and
     quasi-symmetries, combining decomposition and
     aggregation, periodic ordering);
  7. Net-driven Analytical Methods (PNs and product forms,
     linear programming and performance bounds);
  8. Approximate Net-Driven Decomposition Methods
     (product-form approximation, response-time

The lecturers are well-known experts in modelling and
performance evaluation of DEDS. They are involved in
theoretical and applied research and are also collaborating
with industry. They include:

G. Balbo (Torino), B. Baynat (Paris), J. Campos (Zaragoza),
G. Chiola (Genova), Y. Dallery (Paris), S. Donatelli
(Torino), C. Dutheillet (Paris), A. Ferscha (Vienna), G.
Franceschinis (Torino), S. Haddad (Paris), B. Haverkort
(Aachen), U. Herzog (Erlangen-Nuremberg), J. Hillston
(Edimburgh), M. Ribaudo (Torino), M. Sereno (Torino), M.
Silva (Zaragoza), E. Teruel (Zaragoza)

Application domains

   * Manufacturing
   * Transport
   * Telecommunication
   * Concurrent architectures
   * Concurrent programming


   * GreatSPN (GRaphical Editor and Analyzer for Timed and
     Stochastic Petri Nets). A software package for the
     modeling, validation, and performance evaluation of
     distributed systems using Generalized Stochastic Petri
     Nets and their colored extension: Stochastic
     Well-formed Nets. The tool provides a friendly
     framework to experiment with timed Petri net based
     modeling techniques. It implements efficient analysis
     algorithms to allow its use on rather complex
     applications, not only toy examples.
   * SPN2MGM. A tool for specifying stochastic Petri Nets of
     which the underlying Markov chain can be solved using
     matrix-geometric methods.
   * Stochastic Process Algebras, such as TIPP or PEPA are
     compositional specification formalisms discussed within
     the performance school. The TIPPtool aims at realising
     all beneficial aspects of compositional performance
     modelling. It incorporates methods for compositional
     specification as well as solution, based on
     state-of-the-art-techniques, and wrapped in a
     user-friendly graphical front end.


         Detailed Programme of the Performance Models Summer School

     Day     Session             Title               Professors   Hours

 Thursday     a.m.   General presentation           M. Silva        30m.
 3rd                 (*) Basics on stochastic
                     models and QN's (lecture)      Y. Dallery      2h.
                     (**) Basics on PN's (lecture)  E. Teruel       2h.
                     Untimed PN's (lecture)         M. Silva        1h.
              p.m.   Timed and stochastic Petri
                     nets (lecture)                 G. Chiola    
                     Examples and exercises         G. Chiola       1h.
 Friday 4th   a.m.   Logical properties of P/T nets
                     (lecture)                      M. Silva        2h.
                     Performance measures (lecture) J. Campos    
              p.m.   Bounded GSPN's (lecture)       G. Balbo        2h.
                     Introduction to tools (lecture
                     and exercises)                 S. Donatelli    30m.
 Saturday     a.m.   Tools and exercises            S. Donatelli    1h.
 5th                 Well Formed Nets (lecture)    

                     Tools and exercises            G. Franceschinis1h.
              p.m.   Analysis of WFN's (lecture)    C. Dutheillet   2h.
                     Overview of analysis
                     techniques (lecture)           G. Balbo        30m.
 Sunday 6th                          FREE/EXCURSION
 Monday 7th   a.m.   Stochastic process algebras
                     (lecture)                      J. Hillston     2h.
                     Compositionality in
                     SPA's/SPN's (lecture)          H. Hermanns  
              p.m.   Comparison QN's/SPN's
                     (lecture)                      G. Chiola       1h.
                     Simulation (lecture)           A. Ferscha   
 Tuesday 8th  a.m.   Stochastic WFN (lecture and
                     exercises)                     G. Franceschinis30m.
                     Exploiting symmetries
                     (lecture)                      G. Franceschinis1h.
                     Exploiting compositionality
                     (lecture)                      S. Donatelli    2h.
              p.m.   Distributed (asynchronous)
                     simulation (lecture)           A. Ferscha      1h.
                     Distributed (synchronous)
                     simulation (lecture)           A. Ferscha   
 Wednesday    a.m.   Combining composition and
 9th                 aggregation (lecture)          P. Moreaux      2h.
                     Performance bounds (lecture
                     and exercises)                 J. Campos    
              p.m.                      FREE/EXCURSION
 Thursday     a.m.   General approach to
 10th                decomposition based
                     approximation methods          Y. Dallery      1h.
                     Approximation methods I
                     (lecture)                      B. Baynat       1h.
                     Non-exponentially timed nets
                     (lecture)                      G. Balbo     
              p.m.   One place unbounded SPN's
                     (lecture)                      B. Haverkort 
                     Product form solutions I
                     (lecture)                      M. Sereno       1h.
 Friday 11th  a.m.   Product form solutions II
                     (lecture)                      M. Sereno    
                     Approximation methods II
                     (lecture)                      J. Campos       1h.
                     Epsilon-symmetries (lecture)   G. Franceschinis1h.
                                        Closing session

(*) People with some background on PN's.
(**) People with some background on stochastic models and QN's.


    System Engineering. A Petri Net Based Approach to
       Modelling, Verification and Implementation.

          September 14-22, 1998. Jaca, Spain.

                 Scientific Directors:

                C. Girault and R. Valk


Aims and Scope

Formal methods for the specification and verification of
hardware and software systems are becoming more and more
important as systems increase in size and complexity. The
aim of the school is to illustrate progress in formal
methods, based on the Petri net formalism, through a
collection of examples arising from Flexible Manufacturing,
Telecommunication and Workflow Management Systems.

The scope of the school covers several of the main phases of
the life cycle of the design and implementation of a system:
specification, model checking techniques for verification,
analysis of properties, code generation, and execution of
models. The presentation describes these techniques and
their tool support. It identifies and explains fundamental
concepts like composition, abstraction, and reusable models;
model verification and verification of properties. Practical
work with tools will play an important role.


Intended Audience

People interested in the application of Petri nets to
systems engineering. The material and the lectures of the
school will be organized in such a way that the following
two groups of people can benefit from this course:

   * People interested in the application of Petri nets.
     The course starts with a general introduction to
     Petri nets and focuses on the application of Petri
     nets to three application domains: workflow
     management, telecommunication and flexible
   * People interested in the relations between theory
     and practical use of Petri nets.
     The course addresses fundamental modeling problems
     and analysis techniques. State-of-the-art analysis
     techniques are presented for people interested in
     the verification of complex systems.

The course will bring together practitioners, researchers
and PhD students interested in Petri nets. Cases and
concrete projects are used to create a stimulating
atmosphere. People attending the course will be trained
in the use of several computer tools.



  1. Basic Concepts of Petri nets (place transition nets,
     high level nets, examples).
  2. Modelling techniques and methods: (running) examples
     and case studies (from Flexible Manufacturing,
     Telecommunication, Workflow Systems,...).
  3. Tools for Petri nets (presentations and examples).
  4. High Level Petri nets (syntactical aspects,
  5. Properties, Analysis and Verification (safeness and
     fairness properties,...; structural properties and
     subclasses of nets).
  6. Petri nets in specific application domains
     (Manufacturing systems, workflow systems,
     telecommunication systems).
  7. Advanced topics in Analysis and Verification (State
     space based and structural methods).

The lecturers are well known experts in modelling and
verification of DEDS. They are involved in theoretical and
applied research and are also collaborating with industry.
They include:

W. v.d. Aalst (Eindhoven), J.M. Colom (Zaragoza), P.
Estrailler (Paris), J. Ezpeleta (Zaragoza), B. Farwer
(Hamburg), C. Girault (Paris), S. Haddad (Paris), J.M.
Ili (Paris), F. Kordon (Paris), D. Poitrenaud (Paris),
M.O. Stehr (Hamburg), E. Teruel (Zaragoza), R. Valk
(Hamburg), M. Voorhoeve (Eindhoven).


Parts of the course

   1. Introduction to Petri Nets
   2. Applications
        1. WorkFlow Management Systems
        2. Flexible Manufacturing Systems
        3. Formal Design of Telecommunication Services
   3. Advanced topics in Analysis and Verification
        1. Prototyping
        2. State Space Methods
        3. Structural Methods
        4. Deductive Methods
   4. Tools

1. Introduction to Petri Nets

In the past years an increasing demand for precise and graphical
modelling techniques has become visible in almost all fields of
computer applications from industry, commerce and research. 
This is due to growing requirements for efficient and reliable
methods on the one hand and increased power of computer tools 
on the other.

It is thus not surprising that Petri nets have become a common 
technique for the specification, validation and performance 
evaluation of systems, since they provide an intuitive approach, 
formal techniques and graphical description methods.

In the introduction (of the summer school) participants will be 
trained into all these features, starting from a very basic level up
to rather sophisticated skills. This will be possible by means of an 
integrated approach, combining lectures, classroom exercises and 
computer sessions with Petri net tools.

The introduction will start with a general and intuitive notion of Petri
nets and the general principles behind them. Then, an informal tutorial
will introduce the basic models of place/transition nets and high level 
nets, leading to different formal representations to be used in computer
For applications to systems analysis and verification, powerful
mathematical methods, like linear programming, will be employed to 
verify correctness properties like safeness, liveness and reachability.

After the first two days the participant will be prepared to enter the
lessons on particular applications.

2. Applications

2.1 WorkFlow Management Systems

The phenomenon of workflow management will have a tremendous impact on
the next generation of information systems. As the workflow paradigm
continues to infiltrate organizations that need to cope with complex
administrative processes, the WFMS will become a fundamental building 
block. Therefore, the subject workflow management is of utmost 
importance for people involved in the (re)design of administrative 
processes or the development of systems to
support these processes. The Petri net formalism provides a firm
theoretical basis for the modeling and analysis of workflow processes. 
The course addresses the following subjects: workflow management
architecture of workflow management systems, mapping workflow concepts 
onto Petri nets, organizational modeling, verification, and performance 
analysis of workflows.

2.2 Flexible Manufacturing Systems

The design and control of Flexible Manufacturing Systems (FMS) is a very
complex task: many different elements have to be combined, and many
different aspects must be taken into account. This complexity has raised
the need of use of formal models in order to represent and validate the

Petri nets are a family of models well suited for the domain: easy
representation of concurrency and competition relations, application of
different desing strategies, ability to generate code in an automatic
way, a well defined semantics applicable for the qualitative and 
quantitative analysis and a nice graphical user interface.

The aim of the course is to show how Petri nets can be used for the
modeling and analysis of Flexible Manufacturing Systems (focusing 
mainly in qualitative aspects).

2.3 Formal Design of Telecommunication Services

Formal modelling is a key for verification and evaluation of
telecommunication systems. Our application concerns a Multi-Agent System
of contract monitoring. The application acts in the context of the
electronic market. We use a new object-based formalism, which integrates 
the principles of the ODP standard. We transform these high-level 
formalisms into the uniform high level Petri net formalism while 
retaining the original system semantics. The CPN-AMI tools will support 
the modelling and the analysis of this application.

3. Advanced topics in Analysis and Verification

Systems will inevitably grow in scale and functionality. Therefore, the
likelihood of subtle errors is also increasing. A first goal of system
engineering is to take advantage of the investment in modelling to
generate a prototype of the system, and to have an implementation 
consistent with the validated model. A second goal is to provide 
mathematically based methods and tools for verifying such systems.

There exists a diversity of verification methods developed for Petri
nets. This part of the school aims to clarify the bases for choosing an
adequate method for each problem, by discussing issues involved in 
the design and the application of each method: 1) Net models that 
the method is able to verify; 2) Kinds of properties to check; 
3) Families of methods; 4) The interplay of different methods.

3.1 Prototyping

Emphasis will be put on the presentation and discussion of a way to
produce a distributed application from a Petri Net specification. 
The produced application is not a Petri net simulation and can be 
integrated in a complex execution environment.

3.2 State Space Methods

Efficient methods for the construction of the state space are presented
in this tract. Several verification methods working on the state space 
are analyzed and compared.

3.3 Structural Methods

The use of the net structure for formal verification of net properties
is presented. Structural reduction of nets, linear algebra based
techniques, and graph based techniques for net subclasses are the 
main topics.

3.4 Deductive Methods

In this tract the use of logics for formal verification of net
properties is presented. Linear Logic enriched by algebraic 
specifications leads the way to rewriting logic semantics for algebraic 
Petri nets. For verification of
temporal properties of high-level nets a UNITY-style logic is employed.

4. Tools

CPN-AMI is a Petri Net based CASE environment that will be used in the
practical tasks and exercises of the school. It offers a set of services
to ease the work of designers who specify a system by means of the Petri
net theory and benefit from it. It relies on the Macao graph Editor
also behaves as the User Interface of CPN-AMI. This software tool runs
Sparc/SunOS (4.1.4 or later) Sparc/Solaris (2.4 or later) and
UltraSparc/Solaris (2.5.1 or later).

CPN-AMI is a project initiated in 1987 by Professor C.Girault in the
team "Systmes rpartis et coopratifs", in the Laboratoire d'Informatiques
Paris 6 (Previously MASI) in the Universit Pierre & Marie Curie, Paris

The following tools will be used during the course on Workflow
Management Systems to demonstrate the application of Petri-net-based 
software to this domain and which preferably could be used by the 
students for doing assignments:

   * Woflan (Eindhoven University of Technology) for the verification of
     workflow processes made with COSA of PROTOS.
   * COSA BPR-toolkit (Software Ley) The design part of one of the
     leading European workflow products.
   * PROTOS (Pallas Athena) An easy-to-use BPR tool based on Petri nets.
   * ExSpect (Bakkenist) To simulate workflow processes made with COSA
     of PROTOS.


         Detailed Programme of the Systems Engineering Summer School

     Day    Session               Title              Professors  Hours

 Monday 14th  a.m.  Models and toy examples
                    (lecture)                        R. Valk     3h.30m.
              p.m.  Tools presentation and use of
                    toy examples (lecture and        R. Valk and 2h.30m.
                    exercises)                       LIP6
 Tuesday      a.m.  More on High Level Nets
 15th               (lecture)                        C. Girault     1h.
                    More on properties, linear
                    properties and net subclasses    J.M. Colom     2h.
              p.m.  Modelling process (lecture)      M. Voorhoeve
                    Principles and tools for
                    modelling (lecture and           M. Voorhoeve   1h.
 Wednesday    a.m.  Workflow Management Systems
 16th               (lecture and exercises)          W.v.d. Aalst
              p.m.                      FREE/EXCURSION
 Thursday     a.m.  Flexible Manufacturing Systems
 17th               (lecture and exercises)          J. Ezpeleta 
              p.m.  State Space based Methods I      J.M.Ilie,
                    (lecture and exercises)          S.Haddad,   
 Friday 18th  a.m.  Formal Design of
                    Telecommunication Services       P. Estrailler
                    (lecture and exercises)
              p.m.  State Space based Methods II     J.M.Ilie,
                    (lecture and exercises)          S.Haddad,   
 Saturday     a.m.  Structural Methods I (lecture
 19th               and exercises)                   J.M. Colom  
              p.m.  Deductive Methods I (lecture)    B.Farwer,
                    Parallel Laboratory Sessions on
                    Work Flow Management Systems,
                    Flexible Manufacturing Systems   -           
                    and Telecommunication Systems
 Sunday 20th                        FREE/EXCURSION
 Monday 21th  a.m.  Deductive Methods II (lecture    B.Farwer,
                    and exercises)                   M.O.Stehr   
              p.m.  Structural Methods II            E. Teruel   
                    Parallel Laboratory Sessions on
                    Work Flow Management Systems,
                    Flexible Manufacturing Systems   -           
                    and Telecommunication Systems
 Tuesday      a.m.  Prototyping (lecture)            F. Kordon      2h.
 22th               Work Flow Management Systems
                    (lecture)                        W.v.d.Aalst    45m.
                    Flexible Manufacturing Systems
                    (lecture)                        J. Ezpeleta    45m.
              p.m.  Telecommunication Systems
                    (lecture)                        P. Estrailler  45m.
                    Perspectives and concluding
                    remarks                          -              1h.
                    Discussion and clossing          -              45m.



Applicants should fill in the attached application
form and return it

   * by fax to +34.976.762111
   * by regular mail to

     Prof. M. Silva
     Departamento de Informtica e Ingeniera de
     Centro Politcnico Superior de Ingenieros
     Universidad de Zaragoza
     c/Mara de Luna, 3
     E50015 Zaragoza, Spain.

before July 1st, 1998.

Accepted applicants are liable to pay the following
registration fee before July 31th, 1998:

   * Students participating in one school:
        o Total fee (full board included plus
          eventual transport from Zaragoza to Jaca
          and return): 100000 pesetas (ie. approx.
          650 USDs, 1190 DM, 4000 FF, 1170000 liras,
          400 GBP).
        o Granted students should pay only 60 per
          cent: 60000 pesetas (ie. no free access to
          the course and, just symbolically, under
          of his direct comsumptions).
   * Students participating in both schools:
        o Total fee:170000 pesetas.
        o Granted students: 130000 pesetas

International Money Transfer in pesetas to (send
also information of the transfer from your Bank by
fax to +34.976.762111):

Caja de Ahorros de la Inmaculada
Account No.: 2086 0011 48 07 00 2510 77
Agencia No. 11
c/Gran Via, 52
E50005 Zaragoza, Spain

A confirmation of the transfer will be send after
receiving and a receipt will be given at the school.



 Application: before July 1st, 1998
 Payment of registration fee: before July 31th, 1998.


MATCH Advanced Summer Schools
Application Form

O  Mrs      O  Ms      O  Mr

Last Name ..................... First Name .....................

Mailing address and e-mail: ....................................





Highest university degree obtained: ............................

Present professional position: .................................

Institute or company presently affiliated with: ................

Current interests: .............................................

I wish to apply for the following (check one):

   O Performance Models School (100000 pesetas)

   O Systems Engineering School (100000 pesetas)

   O Both Schools (170000 pesetas)

   O I wish to apply for a grant (letter of recommendation, etc.
     enclosed). I   O would    O would not   be prepared to pay
     the full fee in case I will not receive a grant.

If accepted for participation, I will pay my fee, which includes
registration and lodging, before July 31, 1998.

Signature .....................            Date ................



Members of the Organising Committee from the
University of Zaragoza: M. Silva, J. Campos, J. M. Colom, 
J. Ezpeleta, E. Teruel.

For further details please contact:

Prof. M. Silva
Departamento de Informtica e Ingeniera de Sistemas

Centro Politcnico Superior de Ingenieros
Universidad de Zaragoza
c/Mara de Luna No. 3
E50015 Zaragoza, Spain.


JACA (Huesca, Spain)

Jaca is the beautiful capital of a region, the Jacetania,
and belongs to the Comunidad Autonoma ("autonomous
community") of Aragon, northeastern Spain. Situated in
the center of the Pyrenees mountains, on the plateau on
the southern bank of the Aragon River, just south of the
French border, Jaca is close to the "Ordesa National
Park" (the oldest protected natural park in Spain, with a
surface area of about 2,200ha.) and several 3000 meters
high mountains, like "Monte Perdido".

Of ancient origin, the city was captured by the Romans in
194 BC and surrounded by walls, which, with medieval
additions, still partly stand. In 716 it was taken by the
Moors and, under the name of Dyaka, was one of the
principal cities of the region governed from Sarakosta
(modern Zaragoza). Retaken by the Christians in 760, Jaca
was declared a "city" by King Ramiro I of Aragon
(1035-63) and was the first capital of kingdom of Aragon.

Jaca has notable landmarks that include the 11th-century
cathedral; the Citadel (Ciudadela), begun in 1593 and in
a state of perfect preservation; and the town hall in
Plateresque style (1544). The Torre del Reloj ("Clock
Tower") is the permanent site of the Comunidad de Trabajo
de los Pirineos, a groupement of three French Regions
(Aquitaine, Languedoc-Roussillon et Midi-Pyrenees ), four
Spanish Comunidades Autonomas (Aragon, Catalunya, Navarra
y Pais Vasco) and the state of Andorra. In odd-numbered
years, Jaca holds the International Folklore Festival of
the Pyrenees, which takes place around the first week of
August. Apart from folklore groups from the
French-Spanish Pyrenees and from different Spanish
provinces, the most outstanding folklore groups from many
countries of the five continents participate, which is
why it has been called the Folklore Olympics. In Jaca it
is possible to go ice-skating in the Palacio de Hielo.
Jaca's economy is based primarily on agricultural trade
and tourism. Pop. is around 12,000.


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