Page 1 Building Reliable Component-based Systems Chapter 17 - Architectural Support for Reuse...

Building Reliable Component-based Systems Chapter 17 - Architectural Support for Reuse

Chapter 17Chapter 17

Architectural Support for ReuseArchitectural Support for Reuse


OverviewOverview

Industrial Automation Systems

The Motivation for a Platform

The Architecture

Developing a Domain Specific Application


Industrial Automation SystemsIndustrial Automation Systems

Highly specialized, independent, and incompatible hardware and software system solutions.

A flexible combination of basic hardware and software components, communications infrastructure, and application components.


The 6-layer Model of a Technical ProcessThe 6-layer Model of a Technical Process

Group Control Level

ProductionManagement Level

Process Level

Field Level

EnterpriseLevel

Process Control Level


The Motivation for a PlatformThe Motivation for a Platform

Envisioned seamless link between front-end business processes and plant control processes:

Motivations for a large global company to invest into the development of a “single” platform.

Avoidance of parallel developments in different business segments.

Harmonization of the diversity of ‘legacy’ automation platforms acquired through company mergers or resulting from previous parallel developments.

Adoption of product line business strategies (i.e. pursuing a system family concept both within and across vertical market segments).

Implicit expectation of a reuse payoff.


The ArchitectureThe Architecture

AspectObject, Object Type, Aspect and Aspect Type.

Aspect System

A collection of Aspect Types for a certain context or purpose.

Domain-related reuse.

AspectSystemObject

Some Aspect-specific software is needed.

(binary) Software component; Microsoft COM component following specific rules

The basic set of ASOs distributed with the AIP contains functionality for alarming, event handling etc.


AspectObjectsAspectObjects

The most central type of entity in the model

AspectObjects model physical objects

E.g. a specific valve in a dairy (“FIC 201 Valve”)

Does not contain any data

Related data is carried by its Aspects

AspectObjectAspect

Aspect Aspect

Aspect


AspectAspect

Encapsulates a subset of the data related to an AspectObject

Different types of electronic information (e.g. documents)

<<Domain Object>>Valve

<<Aspect Object>>Valve

<<Aspect>>Control

<<Aspect>> Mechanical

Drawing

<<Aspect>> Maintenance Instructions

<<Aspect>>OperatorGraphics

<<is modeled by>>

<<Aspect>>Operation

Report

1 1 1 1 1


Aspect TypesAspect Types

Defines how the data in an Aspect is used

In a “Mechanical Drawing” Aspect, the data is opened with AutoCad

In a “Maintenance Instructions” Aspect, the data is opened with Acrobat Reader

Reuse!+Name : string(idl) = "Mechanical Drawing"+Action : string(idl) = "Open With AutoCad"

Aspect Type

+Data : <unspecified> = 10110100010110010110...

Aspect


Aspect Types, cont.Aspect Types, cont.

+Name : string(idl) = "Mechanical Drawing"+Action : string(idl) = "Open With AutoCad"

Aspect Type

+Data : <unspecified> = 10110100010110010110...

Aspect


Object TypesObject Types

Models the type of an AspectObject

The type of “FIC 201” is “Valve”

Defines what Aspect Types an AspectObject can have

A “Valve” can have a “Mechanical drawing” etc.

Reuse!


Object Types, cont.Object Types, cont.

+Name : string(idl) = "Valve"+Aspects : Aspect Type = "Mechanical Drawing", ...

Object Type

+Name : string(idl) = "FIC 201"+Aspects : Aspect

AspectObject


StructuresStructures

Models a structure

Location structure

Functional structure

Batch structure

...

Typically, each AspectObject is part of several structures


Structures, cont.Structures, cont.


Structures, cont.Structures, cont.

Location structure

Enables browsing through the physical layout

See what valves are physically connected to a pipe

Functional structure

Enables browsing through the functional layout

See what control units are connected to a valve


Physical viewPhysical view

Client-server system

Freedom to choose number of servers

Scalability

Reliability

Freedom to choose number of services


Physical view, cont.Physical view, cont.

WP host

SH C

WP

Server host

ASM

SH A

SH B

WP host

SH C

WP

SH A

SH B

SP A

SP C

Server host

ASM

SP A

SP B

SP C

Server host

ASM

SP A

SP B

SP C

Server/WP host

ASM

SP C

SH C

WP

SH A

SH B

Controller Controller Controller Controller

station network

Controller network

Service group A

Service group B

Service group C1

Service group C2

SP: service provider

SH: service handler

ASM: Afw Service Manager

WP: workplace


Developing a Domain Specific Application Developing a Domain Specific Application

Jacobson et al. have introduced the distinction between an application system and a component system:

Reusing a single component is usually insufficient.

Requires the reuse of a set of components.

A set of components must be reused to obtain the alarm handling functionality.


4-Layer Representation4-Layer Representation

Application system layer:

Offers a coherent set of use cases to some end users.

The business-specific:

Layer several component systems used by the application engineer.

The middleware layer:

Independent of particular types of business

GUI builders, database management systems, etc.

The system software layer:

Operating systems.

Indistinct boundaries between itself and middleware.


AIP Reuse Hierarchy AIP Reuse Hierarchy

W2k

AIP base infrastructure

AIP base ASOsproject specific

ASOs

AIP base Servicesproject specific

Services

AIP built-in admin Aspect Types

project specific Aspect TypesAIP built-in

general-purpose

Aspect Types

AIP built-in admin Object

Types

project specific Object Types

AIP built-in general-

purpose Object Types

domain specific

Aspect Types

domain specific

Object Types

domain specific templates and patterns project specific templates and patterns

enablers

engineering guidelines and

toolsAIP library concept

AIP export/import

OT inheritance

AIP export/import

AT inheritance

COM

VC++

configuration

3rd party applications


Some Words of Caution Some Words of Caution

Possible risks:

Only relying on a platform, not having a reuse-driven process or product line practice with a top-down and planned approach to reuse will not succeed.

Requirements management:

Requirements elicitation, prioritisation and trade-offs across products, domains, and organizational units are extremely complex.

Bugs in a released version

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