A Study on Architecture Description Languages

A Study on Architecture Description Languages

VIETNAM NATIONAL UNIVERSITY, HANOI

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

======

STUDENT SCIENTIFIC RESEARCH CONTEST

Year: 2012

Research name: A Study on Architecture Description Languages

Student name: Pham Van Quy Gender: Male

Class: QH-2008-I/CQ-CA Faculty: Computer Science

Supervisor: Dr.Vo Dinh Hieu

PROJECT SUMMARY

Architecture Description Languages (ADLs) are formal languages that widely used to describe and represent architectures of software systems During a grand development process, many ADLs have been born, such as Wright, xADL, ACME, Aesop, Rapide, UML, etc Almost these ADLs are developed in famous universities all over the world, and they are still under researching to improve to become better and more popular

My study on this subject includes researching on ADLs, a deeper studying into one language, and a demonstration on modeling a system architecture In this report, I

am going to summary my researches on ADLs, which include ADLs definition, ADLs properties and introducing some popular languages Next part is presenting my deeper researches on one languages I have chosen ACME – an architecture description language developed by Carnegie Mellon University – to study its semantic, structure, and syntax Besides studying its theories, I also use ACME to model a system and demonstrate results with support of ACME complier tool - ACME Studio

TABLE OF CONTENTS

I INTRODUCTION 4

1 Introduction 4

2 Research purpose 4

3 Report structure 4

II ARCHITECTURE DESCIPTION LANGUAGES 5

1 Definition 5

2 ADLs in describe system architecture 6

3 Introduce some common language of ADLs 7

III ACME 8

1 Definition 8

2 ACME design element types 8

3 ACME syntax and visualization 10

3.1 Syntax 10

3.2 Visualization 11

4 Some evaluation of ACME 12

IV MODELING WITH ACME 13

1 Student-Course System 14

1.1 Problem definition 14

1.2 Architecture source code 15

2 Building ADL model in ACME 18

2.1 Defining Family 18

2.2 Modeling top-level architecture 18

2.3 Modeling second-level architecture 20

2.4 Final model 21

V CONCLUSION AND FUTURE WORKS 23

VI REFERENCES 23

LIST OF FIGURES

Figure 1: Elements of an ACME description 9

Figure 2: Representations and Properties of a Component 10

Figure 3: Simple Client-Server system in ACME 10

Figure 4: Example illustrate ACME supports hierarchy Hierarchical 11

Figure 5: ACME visualization – ACME Studio 12

Figure 6: Top-level architecture for Student-Course System 14

Figure 7: Student-Course System with ownership domain annotations 16

Figure 8: Ownership Object Graph for Student-Course System 17

Figure 9: Starting new project with Tiered Family type 18

Figure 10: Top-level model of Student-Course System 19

Figure 11: Source code editor of ACME Studio 19

Figure 12: Call-return connection 19

Figure 13: Representation of Logic component 20

Figure 14: Two representation of lock and log component 20

Figure 15: Representation of Data component 21

Figure 16: Student-Course System represented in ACME ADL model 22

I INTRODUCTION

1 Introduction

Architecture Description Languages (ADLs) are formal languages that widely used to describe and represent architectures of software systems An architecture plays several roles in project development, all of them are important, and all of them facilitated by a formal representation of the architecture, such as with an ADL A formal architecture representation is more likely to be maintained and followed than

an informal one, can more readily be consulted and treated as authoritative, and can more easily be transferred to other projects as a core asset

My study on this subject includes researching on ADLs, a deeper studying into one language, and a demonstration on modeling a system architecture In fact, many ADLs have been developed by the academic and industrial communities, and each of them is varied color in the big picture of ADLs For a deeper research, I have chosen ACME – an architecture description language developed by Carnegie Mellon University – to study its semantic, structure, syntax, and use ACME to model a software system with support of its complier tool - ACME Studio[2]

2 Research purposes

For long years development of ADLs, there has been researching from many universities on this field However, almost grand universities works on this subject have developed new languages on their own As a result, there are many languages born but they all have limited number of papers and tutorials, especially ACME

By researching on this subject, on one hand I want to expand my knowledge on

a very interesting field of software engineering; on the other hand, in case my researches have good results, I can go on with publishing my researches This can help increasing resources for ADLs and ACME somehow

3 Report structure

The rest of the report has following structure:

II ARCHITECTURE DESCRIPTION LANGUAGES

1 Definition

2 ADLs in describe system architecture

3 Introduce some common language of ADLs III ACME

1 Definition

2 ACME design element types

3 ACME syntax and visualization 3.1 Syntax

3.2 Visualization

4 Some evaluation of ACME

IV MODELING WITH ACME

1 Student-Course System 1.1 Problem definition 1.2 Architecture source code

2 Building ADL model in ACME 2.1 Defining Family

2.2 Modeling top-level architecture 2.3 Modeling second-level architecture 2.4 Final model

V CONCLUSION AND FUTURE WORKS

In the software engineering community, an Architecture Description Language (ADL)

is a specialized computer languages for explicit modeling and analysis of software architecture

ADL play an important role in software development ADL can be viewed as a platform designed for formal specification of software components It is well-suited

for many purposes, such as design, document, implement and test software components

2 ADLs in describe system architecture

Architecture description languages (ADLs) are widely used to describe system architectures The output of the architecture description process is the system architecture documents This consists of a number of graphical representations of the system model along with associated descriptive text It should describe how the system is structured into sub-system and how each sub-system is structured into components Each component is described based on many properties such as behavior

As others architecture model languages, ADLs have their own positive and negative elements:

Positive elements of ADL

 ADLs represent a formal way of representing architecture

 ADLs are intended to be both human and machine readable

 ADLs support describing a system at a higher level than previously possible

 ADLs permit analysis of architectures – completeness, consistency, ambiguity, and performance

 ADLs can support automatic generation of simulations / software systems Negative elements of ADL

 There is not universal agreement on what ADLs should represent, particularly as regards the behavior of the architecture

 Representations currently in use are relatively difficult to parse and are not supported by commercial tools

 Most ADLs tend to be very vertically optimized toward a particular kind of analysis

 Most ADL work today has been undertaken with academic rather than commercial goals in mind

In fact, most of ADLs is developed under academic researches; as a result, ADLs has many restrictions in real project working In case of UML, it has been

developed under commercial purpose and has become a famous language in software designing

3 Introduce some common language of ADLs

 ACME

The Acme project began in early 1995, by Carnegie Mellon University, with the goal of providing a common language that could be used to support the interchange of architectural descriptions between a variety of architectural design tools Recently, Acme started back as an ADL interchange language but has evolved to an ADL itself

ACME has advantages of general notation, readable by both human and machine, and a strong support of ACME Studio – an well editor and visualization tool

 xADL

xADL 2.0 is a software architecture description language (ADL) developed by the University of California, Irvine for modeling the architecture

of software systems Unlike many other ADLs, xADL 2.0 is defined as a set

of XML schemas This gives xADL 2.0 high extensibility and flexibility, as well as basic support from the many available commercial XML tools

xADL is based on xArch - standard, extensible XML-based representation for software architectures

The UML has well defined formal syntax and semantics and can be machine checked and processed UML includes a set of graphical notation techniques to create abstract models of specific systems

 Wright

Wright is an architecture description language developed at Carnegie Mellon University Wright language focuses on modeling and analysis (specifically, deadlock analysis) of the dynamic behavior of concurrent systems

 Rapide

Rapide (developed by Stanford University) is designed to support component-based development of large, multi-language systems by utilizing architecture definitions as the development framework

There is no best or suggested language Different architectural description languages represent different features and concept of the overall component architectural design problem Therefore, specification a system with varied evaluation concept by single ADL still is a unsolved problem

2 ACME design element types

ACME is built on a core ontology of seven types of entities for architectural

representation: components, connectors, systems, ports, roles, representations and

rep-maps Of the seven types, the most basic elements of architectural description are

component, connector and system

- Components:

Components are the basic building blocks in an Acme description of a system They represent centers of computation: the elements of a system responsible for doing the "work" in a system Components may be used to model both hardware and software or provide an abstraction that may be

mapped to either hardware, software or a combination Intuitively, components correspond to the "boxes" in box and line diagrams Typical examples of components include such things as clients, servers, filters, objects, blackboards, and databases

- Connectors:

Connectors represent interactions among components Informally they provide the ''glue'' for architectural designs, and intuitively, they correspond to the lines in box-and-line descriptions Examples include simple forms of interaction, such as pipes, procedure call, and event broadcast But connectors may also represent more complex interactions, such as a client-server protocol

or a SQL link between a database and an application

Figure 1: Elements of an ACME description

Besides core elements, Properties is also an important element of ACME To

accommodate the wide variety of addition information ACME supports annotation of architectural structure with list of properties Each property has a name, an optional

type, and a value Any elements in ACME can have properties belong with it Here is

an example illustrate diagram of Properties and Representations:

Figure 2: Representations and Properties of a Component

3 ACME syntax and visualization

Since ACME has developed its own library and tool support, ACME can be viewed in both source code and visual model diagram ACME source code has a simple and easy to understand syntaxes; meanwhile, ACME visualization is supported

by a strong tool: ACME Studio – newest version is 3.5.3 for Eclipse 3.7.1[2]

3.1 Syntax

Here is an example of ACME source code which corresponding to model in Figure 2:

Figure 3: Simple Client-Server system in ACME

Explaining:

- As we can see in the example code above, System is declared first and it

contain Components, Connectors and their configuration (Attachments)

- Component: “client” is declared with one port named “send-request”

- Component: “server” is declared with one port named “receive-request”

- An connector “rpc” (stands for remote procedure call) has two roles: caller and

callee These two roles must be plugged into two ports; otherwise, there will be complier error

- Attachments command is configurations of the system that declares which port

is correspond to role of defined connectors

ACME also supports the hierarchical description of architectures It means any component or connector can be represented by one or more detailed, lower-level descriptions

Figure 4: Example illustrate ACME supports hierarchy Hierarchical

Client-Server System

3.2 Visualization

ACME has the advantage that with the introduction of ACME studio, which is

an extension to Eclipse, it provides explicit visualization support to model specific patterns The ACME studio editor provides three views: overview of the files in the project, textual source of the architecture and architecture diagrams with visibility of

modeled patterns To model specific patterns, ACME studio allows one to directly associate pattern elements with their corresponding architecture elements In addition, ACME studio provides visualization support to view pattern elements at both abstract and detail level

Figure 5: ACME visualization – ACME Studio

4 Some evaluation of ACME

Evaluating on four concepts - syntax, visualization, variability, extensibility; architectural description language ACME shows both of its strengths and weaknesses

 Evaluation on syntax (expressing pattern elements, topology, constraints and configuration of components and connectors):

Besides the core ontology of seven basic architecture design elements, ACME provides a template mechanism, which can be used for abstracting common reusable architectural idioms and patterns This can

be a positive element of ACME Using templates and styles help ACME reduces redundant code and increases reusable abilities

 Evaluation on visualization (graphical representation for modeling patterns):

ACME has the advantage that with the introduction of ACME studio, which is an extension to Eclipse, it provides explicit visualization support to model specific patterns It’s the truth that ACME Studio is a strong visualization tool, comparing to other current visualization tool of others ADLs ACME Studio has a good user interface, fast processing and be easy to use

In addition, ACME studio provides visualization support to view pattern elements at both abstract and detail level For instance, a selected component can be easily expanded to view its internal structure by one mouse click

 Evaluation on variability (the ability to express not only individual solutions but the entire space of solution variants):

One weakness of ACME is lack of data types support Currently, ACME, by default, support only Integer, Boolean, and String Although

on purpose of developing an generalized standard for integrating with others ADLs; this flexibility in ACME has a negative impact on analyzing and checking variable error

 Evaluation on extensibility (capability to model new patterns):

In the problem of defining new patterns or resources for system, ACME works quite well Defining new connectors, components, ports, roles…, is an easy step; moreover, ACME also support re-defining the visualization of these elements However, a disadvantage is ACME has not support new connections that require new data types as mentioned above

IV MODELING WITH ACME