PLoP® 2010 Conference Proceeding

PLoP® 2010 Conference Proceedings

17th CONFERENCE ON PATTERN LANGUAGES OF PROGRAMS

October 16th - 18th, 2010, Reno, NV, USA

Proceedings

Download the PLoP 2010 Frontmatter (PDF)

PLoP 2010 is in cooperation with ACM, AGILE, & OOPSLA

Pattern Languages of Programs (PLoP®) conference is a premier event for pattern authors and pattern enthusiasts to gather, discuss and learn more about patterns and software development.

Preliminary versions of these papers were workshopped at Pattern Languages of Programming (PLoP) ’10 October 16 - 18th in Reno, Nevada, USA. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. Copyright is held by the authors.

ISBN: 978-1-4503-0107-7

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Made in the USA

Welcome to PLoP 2010

Welcome to PLoP10, the 17^th Conference on Pattern Languages of Programs, a premier event for pattern authors and pattern enthusiasts to gather, discuss and learn more about patterns, pattern writing, pattern reviewing, shepherding, software development, collaboration, and more, much more.

To accomplish this, the conference program offers a rich set of activities that altogether promote a friendly and effective environment to share expertise, and to give and get feedback from fellow authors. The pre-conference activities start Friday morning (October 15^th) at the BootCamp, a special session aimed at people new to patterns and/or PLoP, led by Robert Hanmer and Linda Rising. The main conference starts on Saturday morning (October 16^th).

Writers' Workshops are the primary focus of our time at PLoP and it will be during them that we will discuss and review each other’s papers in a very fruitful way. We have five groups of five to six papers each, which were selected from an initial set of around 36 submissions, and after a considerable period of shepherding. Papers of the Writing Group will have in addition the
opportunity of being evolved during PLoP with the mentoring of experienced pattern
writers.

We are excited to have keynotes from Joshua Kerievsky about “A Timeless Way Of Communicating: Alexandrian Pattern Languages” and Rebecca Wirfs-Brock who asks: “Nature of Order: Inspiration or Esoteric Distraction?”. Eduardo Guerra will give a presentation about “Framework Evolution: from Inheritance to Metadata“. There will be four focus groups this year which will give opportunity to inspired discussions. Other activities, such as the 'Birds of a Feather' (BoF), let you informally organize your own session about topics you are interested in, or to attend already organized working sessions. Just announce them or subscribe to them!

After the conference, the papers are strongly encouraged to be further evolved in order to
accommodate the suggestions for improvement gathered during the discussions at the
conference. A final version of evolved papers will be published in the ACM Digital Library as PLoP 2010 Proceedings.

This year PLoP is co-located with the SPLASH conference, in the wonderful city of Reno/Tahoe.

And last but not least, we have the Games, a well-established and very important activity at PLoP. Guided by Robert Hanmer, the games will help us all on ice-breaking, to exercise our body and mind, to collaborate better, and to reinforce a community of trust. Some of the games have become ‘traditions', while others will be a surprise. Of course none of these games is related to casino gambling ;-).

We would like to thank all authors, shepherds, reviewers, and Program Committee members for their time and collaboration with PLoP. Thank you!

All of these words just to say that we wish you an amazing and productive time during PLoP10!

Christian Kohls, PLoP 2010 Chair

PLoP 2010 Conference Description

Pattern Languages of Programs (PLoP) conference is a place for pattern authors to have their pattern languages reviewed by fellow authors. The purpose of PloP is to promote development of pattern languages on all aspects of software, including design and programming, software architecture, user interface design, domain modeling, and software process. Domain-specific patterns were encouraged for PLoP 2007.

PLoP 2010 was held in Reno, NV October 16-18th, 2010.

We invited contributions from practitioners and researchers on:

Patterns and pattern languages

Critiques of patterns and pattern languages

Research on patterns and pattern languages

Case studies of the use of patterns and pattern languages

PLoP is different from other conferences. It is run in the "writers' workshop" style, as described in Richard Gabriel's book. Before the conference, authors interact with a "shepherd" who helps them improve their paper to make it as ready for PLoP as possible. A program committee reviews the papers for final acceptance after they have gone through the shepherding process. The writers workshops provide more feedback, and so authors revise their paper again after PLoP. The papers here are the version produced by authors after PLoP, not the ones reviewed at PLoP.

The PLoP '10 conference also hosted presentations concerning a number of hot topics in the patterns community. Following are a list of presentations from PLoP 2010:

"A Timeless Way Of Communicating: Alexandrian Pattern Languages "
by Joshua Kerievsky
"Nature of Order: Inspiration or Esoteric Distraction?"
by Rebecca Wirfs-Brock
"Framework Evolution: from Inheritance to Metadata"
by Eduardo Guerra
"Supporting Alignment of Business and IT using Reference Models and Reference Architectures"
by Jason Hogg
"Focus Group on Patterns Languages: Addressing Challenges"
by Vijay Kumer Eranti, Shivanshu K. Singh, and M.E. Fayad
"Focus Group on Unified Data Mining Engine: Addressing Challenges"
by Shivanshu K. Singh, Vijay Kumer Eranti, and M.E. Fayad
"Focus Group on Organizing Recurring PLoP Events"
by Lise Hvatum

The table of contents is organized by the workshop groups and the chairs as they were presented at PLoP.

Table of Contents

Writers' Workshops
A. 'Frameworks & Environments' group, led by Richard P. Gabriel
"Metaprogramming in Ruby -- A Pattern Catalog" by Sebastian Günther, Marco Fischer "Attack Patterns in VoIP" by Juan C. Pelaez, Eduardo B. Fernandez, Maria M. Larrondo-Petrie, Christian Wieser In VoIP, in order to avoid attacks and discover security vulnerabilities, it is necessary to be aware of typical risks and to have a good understanding of how vulnerabilities can be exploited. In a previous paper we presented the concept of attack patterns. Attack patterns describe from the point of view of the attacker, how a type of attack is performed (what system units it uses and how), analyzes the ways of stopping the attack by enumerating possible security patterns that can be applied for this purpose, and describes how to trace the attack once it has happened by appropriate collection and observation of forensics data. We present a set of attack patterns for VoIP: Denial of Service (DoS), Call Interception, and Theft of Service on VoIP.
"Core Patterns of Object-Oriented Meta-Architectures" by Hugo Sereno Ferreira, Filipe Figueiredo Correia, Joseph Yoder, Ademar Aguiar "Patterns for Access Control in Distributed Systems" by Nelly Delessy, Eduardo B. Fernandez, Maria M. Larrondo-Petrie, Jie Wu Distributed systems introduce a new variety of security threats. The organizations that own them must protect their information assets from attacks. To do this we need to start with highlevel models that represent the security policies of the institution. We present patterns that derive from traditional models: first, the Policy-Based Access Control which models how to decide if a subject is authorized to access an object according to policies defined in a central policy repository. Then we present implementation-oriented patterns that implement the Access Matrix or RBAC model: The ACL pattern allows control access to objects by indicating which subjects can access an object and in what way. There is usually an ACL associated with each object. The Capability pattern allows control access to objects by providing a credential or ticket to be given to a subject for accessing an object in a specific way. Capabilities are given to the principal.
"Design Principles for Internal Domain-Specific Languages: A Pattern Catalog illustrated by Ruby" by Sebastian Günther, Thomas Cleenewerck "Network Congestion Control at the Application Layer" by Paul Adamczyk, Federico Balaguer, Munawar Hafiz, Craig L. Robinson Application-layer protocols play a special role in network programming. Typical programmers are more familiar with them and more likely to implement them. Well-designed application-layer protocols follow many patterns that improve the performance of applications using these protocols. We present a subset of these patterns that focuses on the congestion control at the application layer.
"Architectural Patterns for Metadata-based Frameworks Usage" by Eduardo Guerra, Clovis Fernandes, Fábio Silveira "A Design Pattern for the Transfer of Running Applications between Devices" by Paul Austrem Mobile information systems are growing in acceptance; in order for the vision of true mobility to be realized users must be able to seamlessly move running applications between devices in an adhoc manner. The task of implementing mechanisms to ensure that a running application is successfully moved from one device to another can be considered a generic task, wherein the same fundamental design can be reused. This work tenders a domain specific design pre-pattern that resolves the problems associated with transferring a running application from one device to another whilst maintaining state and tailoring to capabilities. It is meant to aid in the domain of mobile workers, and can be applied as a container between the OS and the applications or as a value-added service by ASPs. The solution adds complexity and imposes conventions on the extendibility of a system, but allows users to maintain state so they can seamlessly move their work between devices.
B. 'Process & Design' group, led by Ralph Johnson
"Persistent State Pattern" by André Saúde, Ricardo Victório, Gabriel Coutinho "SIMD: An Additional Pattern for PLPP (Pattern Language for Parallel Programming)" by Berna L. Massingill, Timothy G. Mattson, Beverly A. Sanders Recent trends in hardware, such as IBM's Cell Broadband Engine and GPUs that can be used for general-purpose computing, have made widely available systems for which a SIMD (Single Instruction, Multiple Data) style of data-parallel programming is appropriate. This paper presents a pattern to help software developers construct parallel programs for environments that support this style of data parallelism. In this approach, the program is viewed as a single thread of control, with implicitly parallel updates to data. This pattern is a new addition to the Pattern Language for Parallel Programming (PLPP) presented in our previous work.
"Observations on the Observer Pattern " by Christian Köppe "A Pattern Story for Aspect-Oriented State Machines" by Mark Mahoney, Tzilla Elrad This paper describes a solution to a real world problem using a combination of well-known patterns. The problem deals with combining implementations of state based behaviors in a loosely coupled manner. The state based behaviors are modeled with state machines and implemented with the State Pattern. The coordination between the loosely coupled state machines is achieved with the Interceptor Pattern. The Abstract Factory Pattern is used to shield the original state machine developers from being aware that their state machines are being combined in new and different ways.
"A Pattern for a Sensor Node" by Anupama Sahu, Eduardo B. Fernandez, Mihaela Cardei, Michael Van Hilst "Design Patterns in Eos" by Hridesh Rajan In earlier work, we showed that the AspectJ notions of aspect and class can be unified in a new module construct that we called the classpect, and that this new model is simpler and able to accommodate a broader set of requirements for modular solutions to complex integration problems. We embodied our unified model in the Eos language design. The main contribution of this paper is a case study, which considers the implementation of the Gang-of-Four (GOF) design patterns [3] in Eos to analyze the effect of new programming language constructs on these implementations. We also compare these implementations with the AspectJ's implementation. Our result shows that the Eos implementation showed improvement in 7 out of 23 design patterns, and are no worse in case of other 16 patterns. These improvements were mainly manifested in being able to realize the intent of the design patterns more clearly. The design structures realized in the Eos implementation provide supporting evidence for the potential benefits of the unified model.
"A Pattern System of Underlying Theories for Process Improvement" by Michael Van Hilst, Eduardo B. Fernandez "Service Delivery & Deployment Design Patterns" by Atul Jain In today's rapidly expanding and highly competitive telecom market, the goal of every service provider is to create and bring to market new, highly adaptive and compelling services which will increase revenue and differentiate them from the competition. From a service user perspective, the consumer expects convenience, ease of use, security and support to be always best connected. Services are getting decoupled from the underlying network infrastructure delivering those services leading to a true service oriented architecture and subscriber-centric approach to service delivery. This paper attempts to bring few patterns that are fundamental to the design of evolving service networks.
"Parameterized Strategy Pattern" by Ognjen Sobajic, Mahmood Moussavi, Behrouz Far
C. 'People & Ideas' group, led by Linda Rising
"Additional Patterns for Fearless Change III" by Mary Lynn Manns, Linda Rising "SIMD: An Additional Pattern for PLPP (Pattern Language for Parallel Programming)" by Berna L. Massingill, Timothy G. Mattson, Beverly A. Sanders Recent trends in hardware, such as IBM's Cell Broadband Engine and GPUs that can be used for general-purpose computing, have made widely available systems for which a SIMD (Single Instruction, Multiple Data) style of data-parallel programming is appropriate. This paper presents a pattern to help software developers construct parallel programs for environments that support this style of data parallelism. In this approach, the program is viewed as a single thread of control, with implicitly parallel updates to data. This pattern is a new addition to the Pattern Language for Parallel Programming (PLPP) presented in our previous work.
"Patterns for Organizing PLoP" by Lise Hvatum "Patterns for Refactoring to Aspects: an incipient Pattern Language" by Miguel Pessoa Monteiro, Ademar Aguiar Aspect-Oriented Programming is an emergent programming paradigm providing novel constructs that eliminate code scattering and tangling by modularizing crosscutting concerns in their own aspect modules. Many current aspect-oriented languages are backwards compatible extensions to existing, popular languages, which opens the way to aspectize systems written in those languages. This paper contributes with the beginnings of a pattern language for refactoring existing systems into aspect-oriented versions of those systems. The pattern language covers the early assessment and decision stages: when it is feasible to refactor to aspects, assessment of the necessary pre-requisites and establishing the desirable strategy for the refactoring process.
"The Structure of Patterns" by Christian Kohls "A Pattern Story for Aspect-Oriented State Machines" by Mark Mahoney, Tzilla Elrad This paper describes a solution to a real world problem using a combination of well-known patterns. The problem deals with combining implementations of state based behaviors in a loosely coupled manner. The state based behaviors are modeled with state machines and implemented with the State Pattern. The coordination between the loosely coupled state machines is achieved with the Interceptor Pattern. The Abstract Factory Pattern is used to shield the original state machine developers from being aware that their state machines are being combined in new and different ways.
"Patterns for Sustainable Development" by Linda Rising, Karl Rehmer "Service Delivery & Deployment Design Patterns" by Atul Jain In today's rapidly expanding and highly competitive telecom market, the goal of every service provider is to create and bring to market new, highly adaptive and compelling services which will increase revenue and differentiate them from the competition. From a service user perspective, the consumer expects convenience, ease of use, security and support to be always best connected. Services are getting decoupled from the underlying network infrastructure delivering those services leading to a true service oriented architecture and subscriber-centric approach to service delivery. This paper attempts to bring few patterns that are fundamental to the design of evolving service networks.
"Patterns for Online Discussions" by Jill O'Sullivan, Raul Zevallos
D. 'Security & Systems' group, led by Rebecca Wirfs-Brock
"Towards a Pattern Language for FLOSS Development" by Christoph Hannebauer, Vincent Wolff-Marting, Volker Gruhn "SIMD: An Additional Pattern for PLPP (Pattern Language for Parallel Programming)" by Berna L. Massingill, Timothy G. Mattson, Beverly A. Sanders Recent trends in hardware, such as IBM's Cell Broadband Engine and GPUs that can be used for general-purpose computing, have made widely available systems for which a SIMD (Single Instruction, Multiple Data) style of data-parallel programming is appropriate. This paper presents a pattern to help software developers construct parallel programs for environments that support this style of data parallelism. In this approach, the program is viewed as a single thread of control, with implicitly parallel updates to data. This pattern is a new addition to the Pattern Language for Parallel Programming (PLPP) presented in our previous work.
"Dynamic Model Evolution" by Atzmon Hen-Tov, David H. Lorenz, Lena Nikolaev, Lior Schachter, Rebecca Wirfs-Brock, Joseph W. Yoder "Patterns for Refactoring to Aspects: an incipient Pattern Language" by Miguel Pessoa Monteiro, Ademar Aguiar Aspect-Oriented Programming is an emergent programming paradigm providing novel constructs that eliminate code scattering and tangling by modularizing crosscutting concerns in their own aspect modules. Many current aspect-oriented languages are backwards compatible extensions to existing, popular languages, which opens the way to aspectize systems written in those languages. This paper contributes with the beginnings of a pattern language for refactoring existing systems into aspect-oriented versions of those systems. The pattern language covers the early assessment and decision stages: when it is feasible to refactor to aspects, assessment of the necessary pre-requisites and establishing the desirable strategy for the refactoring process.
"A Security Pattern for Data Integrity in P2P Systems" by Benjamin Schleinzer, Nobukazu Yoshioka "Design Patterns in Eos" by Hridesh Rajan In earlier work, we showed that the AspectJ notions of aspect and class can be unified in a new module construct that we called the classpect, and that this new model is simpler and able to accommodate a broader set of requirements for modular solutions to complex integration problems. We embodied our unified model in the Eos language design. The main contribution of this paper is a case study, which considers the implementation of the Gang-of-Four (GOF) design patterns [3] in Eos to analyze the effect of new programming language constructs on these implementations. We also compare these implementations with the AspectJ's implementation. Our result shows that the Eos implementation showed improvement in 7 out of 23 design patterns, and are no worse in case of other 16 patterns. These improvements were mainly manifested in being able to realize the intent of the design patterns more clearly. The design structures realized in the Eos implementation provide supporting evidence for the potential benefits of the unified model.
"Secure Chained Observer Pattern in Distributed Systems" by Vivek Gondi and Datta G "Service Delivery & Deployment Design Patterns" by Atul Jain In today's rapidly expanding and highly competitive telecom market, the goal of every service provider is to create and bring to market new, highly adaptive and compelling services which will increase revenue and differentiate them from the competition. From a service user perspective, the consumer expects convenience, ease of use, security and support to be always best connected. Services are getting decoupled from the underlying network infrastructure delivering those services leading to a true service oriented architecture and subscriber-centric approach to service delivery. This paper attempts to bring few patterns that are fundamental to the design of evolving service networks.
E. 'Reliability & Trust' group, led by Robert Hanmer
"Patterns for Building Dependable Systems with Trusted Bases" by Eunsuk Kang and Daniel Jackson "SIMD: An Additional Pattern for PLPP (Pattern Language for Parallel Programming)" by Berna L. Massingill, Timothy G. Mattson, Beverly A. Sanders Recent trends in hardware, such as IBM's Cell Broadband Engine and GPUs that can be used for general-purpose computing, have made widely available systems for which a SIMD (Single Instruction, Multiple Data) style of data-parallel programming is appropriate. This paper presents a pattern to help software developers construct parallel programs for environments that support this style of data parallelism. In this approach, the program is viewed as a single thread of control, with implicitly parallel updates to data. This pattern is a new addition to the Pattern Language for Parallel Programming (PLPP) presented in our previous work.
"Patterns for Measuring Performance-Related QoS Properties in Service-Oriented Systems" by Ernst Oberortner, Uwe Zdun, Schahram Dustdar "Patterns for Refactoring to Aspects: an incipient Pattern Language" by Miguel Pessoa Monteiro, Ademar Aguiar Aspect-Oriented Programming is an emergent programming paradigm providing novel constructs that eliminate code scattering and tangling by modularizing crosscutting concerns in their own aspect modules. Many current aspect-oriented languages are backwards compatible extensions to existing, popular languages, which opens the way to aspectize systems written in those languages. This paper contributes with the beginnings of a pattern language for refactoring existing systems into aspect-oriented versions of those systems. The pattern language covers the early assessment and decision stages: when it is feasible to refactor to aspects, assessment of the necessary pre-requisites and establishing the desirable strategy for the refactoring process.
"Software Rejuvenation" by Robert Hanmer "A Pattern Story for Aspect-Oriented State Machines" by Mark Mahoney, Tzilla Elrad This paper describes a solution to a real world problem using a combination of well-known patterns. The problem deals with combining implementations of state based behaviors in a loosely coupled manner. The state based behaviors are modeled with state machines and implemented with the State Pattern. The coordination between the loosely coupled state machines is achieved with the Interceptor Pattern. The Abstract Factory Pattern is used to shield the original state machine developers from being aware that their state machines are being combined in new and different ways.
"Sharing Bad Practices in Design to Improve the Use of Patterns" by Cédric Bouhours, Hervé Leblanc, Christian Percebois "Design Patterns in Eos" by Hridesh Rajan In earlier work, we showed that the AspectJ notions of aspect and class can be unified in a new module construct that we called the classpect, and that this new model is simpler and able to accommodate a broader set of requirements for modular solutions to complex integration problems. We embodied our unified model in the Eos language design. The main contribution of this paper is a case study, which considers the implementation of the Gang-of-Four (GOF) design patterns [3] in Eos to analyze the effect of new programming language constructs on these implementations. We also compare these implementations with the AspectJ's implementation. Our result shows that the Eos implementation showed improvement in 7 out of 23 design patterns, and are no worse in case of other 16 patterns. These improvements were mainly manifested in being able to realize the intent of the design patterns more clearly. The design structures realized in the Eos implementation provide supporting evidence for the potential benefits of the unified model.
"Pattern-oriented Knowledge Model for Architecture Design" by Kiran Kumar, Prabhakar T.V. "Service Delivery & Deployment Design Patterns" by Atul Jain In today's rapidly expanding and highly competitive telecom market, the goal of every service provider is to create and bring to market new, highly adaptive and compelling services which will increase revenue and differentiate them from the competition. From a service user perspective, the consumer expects convenience, ease of use, security and support to be always best connected. Services are getting decoupled from the underlying network infrastructure delivering those services leading to a true service oriented architecture and subscriber-centric approach to service delivery. This paper attempts to bring few patterns that are fundamental to the design of evolving service networks.
"The AnyCorrectiveAction Stable Design Pattern" by Shivanshu Singh, Mohamed Fayad

Committees

The PLoP Conference would not be a success without the volunteer help of the shepherds and program committee members. The shepherds devote hours of their time to helping authors improve their papers pre-conference. The program committee members help organize the conference, handle requests, and communicate with attendees.

We would like to thank all those who helped make PLoP 2010 a complete success.

Conference Organization Committees

Conference Chair	Christian Kohls
Publicity & BootCamp	Linda Rising(Independent Consultant, USA) Bob Hanmer (Alcatel-Lucent, USA)
Publications	Pam Rostal
Director of Local Operations	Joseph Yoder (The Refactory Inc., USA)
Registrations	Jason Frye (Hillside Group, USA)
Web Design	Ana Ferreira Miguel Carvalhais (id:D / FBAUP, Portugal) Jason Frye (Hillside Group, USA)