A Comparative Study of Software Component Models for Embedded Systems

A Comparative Study of Software Component Models for Embedded Real Time SystemsStudent:

Imran AfzalMSc Computer Science with Software Engineering Profile

Department of Computer Science and Electronics (IDE)

Mlardalen University, Sweden

ain05001@student.mdh.se

Supervisor:

Frank LdersDepartment of Computer Science and Electronics (IDE)

Mlardalen University, Sweden

frank.luders@mdh.se

Examiner:

Ivica Crnkovic

Department of Computer Science and Electronics (IDE)

Mlardalen University, Sweden

ivica.crnkovic@mdh.se

Master Thesis (D Level)

Abstract

It is no doubt that at the moment time is so important for every one in every kind of field. So it is the requirement of time to produce suck kind of products which consumes les time. But now it is right to say that there are such products available in market which really changes our lives. At the moment every manufacturing company trying to use such kind of CPUs that really helps to develop the embedded systems. Even if we observe our daily life we find such kind of thing s which we really ignored uses embedded systems. At the moment there are different components are used to develop the embedded systems. The most important component at the moment is Koala component which is developed by the Philips. Philips used Koala in developing the consumer electronic products. Koala has its own characteristics due to which Philips used it. There are also real time embedded systems which use such kind of components. There are different kinds of real time systems. There is a main idea behind real time system that they have to reply in a specific time to a specific task. There is a complete a life cycle of the real time systems. There are also different areas in which embedded systems are used at the moment. There is main advantage of Koala components that there are different graphical functions for different files even up to 100Mbps.

Acknowledgements

With the name of Allah Almighty who is most beneficent and merciful. First I would like to thank my supervisor Frank Luder due to his kindness and help which really courage me to complete my thesis within the time. I am also thankful to Christen Sandberg who really helps me in finding the room because such kind of work really needs your full attention. I specially thanks to my Pakistani Friends who really help me during my whole effort. A very special thanks to my whole family because they really courage me to do some thing. The most important person in my family is my uncle Muhammad Afzal who really courage me and put his all efforts to me. I am proud of being his Son because I think that if I am at this stage due his efforts. He has a great dream to see me successful in my life. I hope that I will fulfill my uncles Dream.

41 Introduction

52 Embedded Real Time Systems

52.1 History of Embedded Systems

62.2 What is Embedded System?

62.3 What is Real Time System?

62.4 Areas of Use

73 The koala Component Model

73.1 What is Koala?

73.2 Koala Language

73.2.1 Requirements

83.2.2 General Concepts

83.2.3 Binding and Bind Time

83.2.4 Koala Components

83.2.5 Diversity interfaces

93.2.6 Product-Line Architecture

103.2.7 Creating Products

103.2.8 Handling Versions and Variants

113.3 Koala Component Model for Consumer Electronics Software

113.3 Koala Model

113.3.1 Component

113.3.2 Implementation

123.4 Koala Features

134 From objected-oriented Programming to COM

134.1 Object Oriented Programming

144.2 What is a Component?

144.3 Component Object Model (COM)

154.4 Comparing OOP and COM

165 Component Based Embedded Systems

175.1 Framework for Component-Based Embedded Systems

176 Component-Based Software Engineering

176.1 Component Requirement Analysis

186.2 Component Development

186.3 Certification of Component

196.4 Customization of Components

206.5 Designing System Architecture

206.6 Integration of the System

216.7 Testing of System

226.8 Maintenance of System

226.9 Quality Assurance for Component-Based Embedded Systems

226.9.1 Life Cycle

236.9.2 Quality Characteristics of Components

237 Conclusion

258 References

1 Introduction

A large area of computer systems is occupied by different types of embedded systems. Now we can say that above 90% of the CPUs are used in the development of embedded systems. In the whole part of these embedded systems there are different categories including very small and large systems as well. We all know that now there are a lot of embedded systems involved in every kind of business. Even if we consider our daily life there are a lot of embedded systems involved like Alarm Clock, Break Fast Machine, Home Safety System, Traffic System, Automatic Doors, Telephone, Television, Mp3 Players, Camera, PDA, Printer, Scanner and Mobile etc As we all know that the Automobile industry in the world is increasing day by day. If we consider an example of a Car, we will be surprised to know that there are such a huge number of embedded systems involved in a car. A latest model of can have round about 70 processors for different purposes like Engine Control, Audio, A/C control, etc Embedded Systems are mostly Processor based like General Processors, Micro Processors and DSP. Real Time systems are mostly responsible to deliver the correct results and also the time to deliver these results as well. We can consider a result as wrong result if it does not meet the time line of the result i.e. Late result = Wrong result. According to IEEE the definition of Embedded systems look like An Embedded Computer System: A computer system that is part of a larger system and performs some of the requirements of that system; for example, a computer system used in an aircraft or rapid transit system. (IEEE, 1992).[5] Now according to IEEE definition it could be considered that such kind of embedded systems are just like real time systems. The reason behind such kind of real time systems is that the result of system, because here we also consider the time factors to achieve the result except that we consider the logical factors. Now we can define Embedded real time systems that A system in which computer performs as a part of a large system and interact with external devices directly. In general it is better to say that the use of component based technologies is better in development of embedded systems. There are also different design requirements for general purpose and embedded systems. Like for general purpose systems we have to consider the performance only. But for Embedded system we have to consider a lot of things like Timing, Cost sensitivity, Power consumption, Size and Weight, Safety and Reliability and Time to market. We also have to consider component acquisition, compatibilities, upgrades etc COM and Koala are two different component models used for different purposes. COM is mostly used for general purpose model. Mostly we use COM in desktop and IS domains. But on the other hand Koala is mostly used for the development of embedded systems now a day. Koala Component technology is basically introduced and used by Philips. Philips used Koala components in the development of software in consumer electronics. There is model through which most Koala components interact is called pipes-and-filters. Then the result of this model is used by different threads. There is another component technology which is alternate to the koala component technology called Robocop component technology. The main purpose of this technology is just to cover the different aspects of embedded systems development. There is also a technology for the development of small embedded systems, developed by Arcticus systems is Robus Component Model. At the moment this technology is used by Volvo Construction Equipment. Now we can say that there are different Component Models used for the development of embedded systems. Every one tries to develop such an efficient system which consumes less time. Some one can ask that why we do not use one component for embedded systems. But experiences have shown that different component have different characteristics. As we know that different platforms require different requirements at different levels so we try to use such a system which cover more of the requirements. Now just because of such reasons we use different components for the development of embedded systems but the basic principle behind the development never changes. 2 Embedded Real Time Systems

Generally speaking embedded systems represent some general functionality. Now the reason behind the using of CPUs is basically due to complex functionalities of embedded systems. Now there are embedded systems both for ultra small systems and for huge systems as well. It is also a true factor that there are different requirements for both the systems. Due to this reason different characteristics of embedded systems refer to its requirements. In the mean time there are also some non-functional characteristics due to which design of an embedded system becomes challenge e.g.

A system fails if it does not meet the real time dead line. In real time properties there are also response time, time to execute in worst case, general execution time, deadline etc We mentioned that there different requirements for small and large systems, so it concerns with the resource consumption. Now the main issue behind this requirement is the size of the system. There is another requirement of the embedded system is considered with its time period i.e. Life Cycle. We know that embedded system is a part of a computer system so normally an embedded system has a very strong connection with its environment. There are such embedded systems available in the market having long life in different fields. The main advantage of long life is to reuse the software and hardware technologies. It is necessary for a long life system to accept these challenges. Some time we have to concern with low power consumption. To reduce the size of code we have to concern with low manufacturing cost.

Mostly there are limited resources in embedded devices. In such kind of limitations there are certain important things like memory, power of processing and also the power related to battery. If we compare with other domains then it is difficult to increase the resources from different aspects like technically and economically. [6]There are such embedded systems available now in which the interaction with hardware devices is very obvious. [6]2.1 History of Embedded Systems

There were some embedded systems in the beginning of 60s but Apollo Guidance was the first modern embedded system. It was such an important embedded system that every flight towards moon needs two such kind of embedded systems. When Apollo Project was under development Apollo Guidance Computer performs a very big role and also it was considered as a huge risk to use it. But then they also need to reduce the size and weight as well. Now due to this reason the risk increased very much. Then the first mass-produced embedded system released in 1961 known as D-17. Actually it was a guidance computer used for the Minuteman missile. [3]

2.2 What is Embedded System?

We can define an embedded system as a computing device without any controlling device like key board, mouse etc It is not the responsibility of Embedded Systems to provide the standard computing devices. In general we can define an embedded system as a computing system carrying strong hardware and software integration which we use to perform a devoted function. But it is subjective definition of embedded systems. It is just because of such systems which are integral part of another system i.e. system within a system. Such kind of embedded systems can find normally in daily entertainment devices like digital set-top box (DST). A/V decoder is an example of such kind of embedded systems because it is an integral part of the DST. As we know the working of A/V decoder that it takes single multimedia stream as input and it generates audio and video frames as output. But some time embedded systems work as a stand alone system like router.

Some important examples of embedded systems are Personal Computers, ATMs, Environmental Monitoring Equipment, Heating System, Cooling System, Ventilating System, Security System, Elevators, Robotics, Global Positioning System (GPSs), Real Time Control Systems Supervisory and Data Acquisition.[2]

2.3 What is Real Time System?

There is an important aspect of every Real Time System (RTS) is to meet the time line. Every RTS has to respond a certain set of external inputs. Then RTS has to process these inputs and finally responds to control different peripherals connected with system after taking the appropriate decisions. There is also a definition of RTS by Donald Gilles that A real-time system is one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time in which the result is produced. If the timing constraints are not met, system failure is said to have occurred. [4] It is necessary that the design of RTS specifies the timing requirement. RTS also have to ensure that its performance will be correct and according to time. If we consider the time constraints there are three types of time constraints.

Hard: if the system replies late and also incorrect then it shows that the system is failed. The example is medical equipment used for the monitoring of human body.

Soft: if the RTS response within an average time as defined by the requirements. The example of such RTS is airline reservation system.

Firm: if RTS has both the properties of Hard and Soft. The example of such a RTS is patient ventilator.

2.4 Areas of Use

In the era of Component development the use of embedded systems is very common in almost every field of life. Every manufacturing company is trying to use the component technologies to develop different kind of embedded systems. Figure 2.0 illustrates the use of embedded systems in different aspects of life. From figure it clear that mostly we use embedded systems in Communication/Telecommunication/ Networking fields. Also there are 10% embedded systems are used in other different domains like in our daily life.

Figure 2.0 Overview of Using Embedded System in Different Areas [1]

3 The koala Component Model

3.1 What is Koala?

Actually Koala is a small animal who likes to climb. But I have no concern with that animal because I have to work on Koala Component technology which is developed and used by Philips. There are some main aspects related to Koala Language. Koala is basically a component model and a language which describes the architecture and it is used to develop a lot of products by using different kinds of component.

3.2 Koala Language

There are certain important aspects in Koala language. [13]

3.2.1 Requirements

When Koala was designed there were three main requirements found in 1996. As Koala used to develop different products so they develop a technique through which different components could be easily composed into different products. This technique is used as the main approach in developing different products. The following technique should be able to work in an environment like resource-constrained e.g. television and video recorders etc.

In order to control the complexity of products the architecture should be precise as much as possible.

3.2.2 General Concepts

There is a small set which is known as inter face and consist of small set of elements related semantically. Type interface describes the syntax and semantic of related elements. There is an interface instance which is used to implement an interface within a component. The component is used as a unit for reusing. There is a unit of code known as module. But it is always a part of component. To connect an interface to another interface we need a cable or interface binding. It is also used to connect an interface to module or module to an interface. There could be a situation that we have to connect a list of interfaces to another special list of interfaces then we need a switch. Finally we also need a place to store all components, interfaces and data type definitions known as repository.

3.2.3 Binding and Bind Time

The concept of binding and bind time could be easily understood by an example described. We consider a product P having two different components A and B and also consider that A uses B. Now if A uses B then its mean that A has the right to call a function of B. It is also clear that both the components are compiled separately. But the call of A is bound by a linker to use the functions in B. There are two possibilities of occurring binding like Link Time and some time Run Time as well. As there are different component technologies which usually arrange runtime binding to accomplish the product binding. In such kind of situations component A use a pointer to a function. Mostly Koala is used in such a resource-constrained environment. In such kind of environment mostly binding is known and fixed at product time above 90% but such kind of binding varies from product to product.

3.2.4 Koala Components

A component of Koala contains a code and interacts with its environment but only in one way which is identified as Explicit. There are different Koala components but they have no connection with each other i.e. they are independent. The configuration of Koala consists of components list and also a list of connections between different components. There is also a third party involved in the working of component A and B to work together. The result of A and B points to configuration C known as third party binding. Configuration has no interfaces around border and it is just a top level component. There are different products which have different kinds of component. There is also possibility of using different instances of a specific component type. Such concept is known as multiple instantiation. To describe the connections between components interfaces are used. Similar to COM and Java, there are different related functions contained in an interface. Definition of interface is used to describe the prototype and semantic of functions. On the other hand components need the instances of interfaces. Interfaces provided by Koala are similar as provided by COM and Java. A single component of Koala can provide a lot of interfaces. There is also some Koala components which contain require interfaces, such kind of interfaces used to communicate with its components environment by using explicit connection points. These kinds of components are controlled by a third party. This concept is present in COM but its optional to use.

3.2.5 Diversity interfaces

To parameterized different components of Koala there are diversity interfaces. But there is no such a specific method for this purpose in Koala. It can be performed by using any technique of binding in Koala by bounding requires interfaces. There are also some expressions in Koala which are used for optimization reasons. By using such kind method it could be possible to introduce a component specific set of parameters. It is very important to know that there are such kinds of software available in the market now in which diversity products are known by the components at low-level.

3.2.6 Product-Line Architecture

To gather different kinds of components by using the provided services to match required services, Koala has such facilities to perform such kind of operations. But there is an important condition to perform such kind of operation that all the components follow the Koala model. There are also possibilities in Koala that architectural components do not match each other. To avoid such kind of mismatches it is necessary to define a set of simple architectural rules. There should be an initialization interface provided by all kinds of components. There are different components in Koala model so every component has its own interface. The component that can not control the hardware specifies a very simple interface like IInit that has only a single function init. Such kind of components also provides some complicated functions as well like IPower. Sometimes there are such situations that a majority of components require functionality of other components while initializing. There is another rule in Koala Model which concerns with Multithreading. There are a lot of small and independent activities in different kinds of control software used for consumer electronics. A basic example of such kind of activities is a control loop which is used to control and measure the quality of image. Such kinds of activities have different behaviors like hard, relatively hard and soft in real time systems. To differentiate between high level and low level frequency tasks we use a real time kernel having anticipatory scheduling. But there are still two problems arises

As reusable components are different for different products so it is complicated for them to make so many assumptions regarding the architecture of the products. Now there is a technique to solve the first problem known as thread sharing. There are different software having different activities use pumps, and to process the message there are different message queues with different functions and to activate the pump function there is also a logical thread as well. There are different pump engines which serve as physically threads and also control the pumps. Such a technique can also be used as a solution to the second problem. Third rule in Koala Model is known as notification. The example of such kind of rule is a TV system. If the broad cast does not receive signals then there must be a sign of error like no sound etc There is also another example related to this rule is the searching of frequency for the next available station. Now such kind of action could take few seconds or one minute as well. So there should be some response about the search either the station is found or not. In different products the sign of notification is attached to a single client but it could be different for different products. To differentiate these notifications we have to model these notifications as outcalls by using optional requires interfaces. We can differentiate the whole architecture of the product into three different layers

A computing platform layer is developed to utilize the hardware implementation.

A platform related to an A/V/data is developed to utilize the audio, video and data processing hardware.

There are also some layers of applications and services as well. There are different components related to these three layers which can use the components of each other. Like the components of first layer could be used by the components related to second layer. At the same time components related to both first and second layer could be used by the components of third layer. To control a specific subdomain there is a specific set of subsystems obtained by every layer.

3.2.7 Creating Products

There are different components involved in Koala Model which are stored in a storage area known as repository. The repository is such a storage area that contains a set of packages. These packages also contain different items like set of components and interface definitions but theses are different from each other by their type like Public or Private. Now only one team can develop a package also in one location as well. The process of creating product is not very difficult. To create a product first of all a private directory structure is used to download a subset of packages. After this process a top level definition of component is created. Due to this process it becomes easy to instantiates and binds different components from that storage place which is known as repository. Mostly compound components are used in this process. Now from here it is decided that either the product is developed or not, if the product requirements do not match the existing component then from basic components we can create the new components. Also there is another situation when the existing basic components does not meet the requirements then we have to create new basic components. The whole process to generate the product is known as bottom up approach.

3.2.8 Handling Versions and Variants

There is a domain of system to handle the variants and versions of different components and products which is called Configuration Management. There are two main reasons due to which it could be difficult to handle the diversity present in a product by CM system. Some time we believe that diversity is a very important part of basic architecture of the product but CM system does not allow the diversity to keep inside the architecture normally in practice. There are such a products developing now or in future where we have to handle the maximum diversity at runtime but in the mean while it is very difficult for CM system to handle the diversity at runtime because CM system can only handle at compile time. Due to these reasons there are certain aspects which arise.

We use such a CM system which has complete rights to control our software; there should also source code and documentation issues be involved.

There is another possibility that we do not use the CM system for permanent branches but also use for products having very short life.

There is another issue that for all permanent diversity present in different developing products we use only Koala model. Now as we already know that a single team has the responsibility of each package at only single location but now it is also known that the CM system of each package maintained by itself as well. Now due to this characteristic it is possible that all the files of a package in its full version maintained by the specific package CM system. In the mean while the customers of that package have the access to its normal releases. The consistency issues with in that package have to maintained by development team of that package so the users do not have any concern the consistency of the package. They just have to concern with consistency between the different packages. To handle the variation within a package there are different Koala compound components which vary from product to product. 3.3 Koala Component Model for Consumer Electronics Software

To develop different software related to consumer electronics, object-oriented approach is ideal to use. A lot of Consumer Electronics (CE) using at present include embedded systems. As the CE start developing there were not so many challenges but a few years ago there were three major problems as described

First there was a problem related to the size and complexity of software using in developing individual products.

The second major problem related to developing products is diversity of products and also software used to develop that product.

The third major factor was related to the time of development.

3.3 Koala Model

In the designing phase of Koala there is a difference between component and configuration development. Builders of component do not make any kind of assumption related to configurations. The reason behind this issue is that components are used in configuration. In the same way the designers related to configuration are not allowed to make changes according to their requirement in components.

3.3.1 Component

Components of koala are combination of different things like design, development and reusing is most important. As it is described earlier that interfaces are used by components to communicate with its environment. There are a lot of functionalities provided by a component by using an interface. In considered model, require interfaces are used to access every kind of peripheral functionality. Such kind of interfaces is also used to access the general services including memory management. The example of such kind of interfaces is TV. As in TV there is a tuner (hardware device) that receives signals through antenna as input and then filters all the signals to find the required station and finally generates the output signal at a transitional frequency. There is description language to define the component boundaries known as Component Description Language (CDL). There are two different names are used to label the interface like long and other.

3.3.2 Implementation

In koala all components are independently designed. Interfaces are used to communicate each other. At the time of configuration the binding of interfaces is late. There is a header file generated by Koala with renaming macros as shown in figure 8.0 [10]

8.0 Overview of Static Binding Implementation

3.4 Koala Features

One of the important tools using for Koala is Koala Viewer. There are certain vital features of Koala Viewer as described [11]

Designers have different experiences with Koala like testing and designing for other designers.

For over four years Koala has been tested in different ways. From different testing experiences it has been confirmed that Up-and-running-times of above hundred hours is common even with a lot of simulation updates.

There is another feature related to output of Koala which assures that the development with Koala is very rapid. There are different graphical functions in Koala for a huge number of simulation files which are over 100Mbps have been optimized.

Another feature is related to user friendly environment. Like there are a lot of function used by mouse and keyboard.

There are different standard formats related to industry in which some are described below

Meta-Software-Hspice (binary)

Start-Hspice (ascii and binary, .ac .sw .mt)

Smart-Spice (float, xdr and double)

Berkeley-Spice (ascii and binary)

Raw (a format of Koala)

Mud-Pack (tool for analysis of power-network)

There are also different ways to write Koala like

Matlab (ascii)

Raw

In Koala for enabling the offline-functions and also for saving the configuration there is a simple scripting language is used.

There is an advanced bus-editor used in Koala but not originate in different available tools using at commercial level. Bus-editor is used in Koala for a specific purpose like to convert the signals from analog to digital quantized.

In Koala there are a lot of internal functions are used like

To perform arithmetic functions there are different arithmetic operators like +,*,-, /, % etc

To perform different logical operations there are different logical operators like! ^ | &

There are operators used for equalizing/nonequalizing like < > ^^

There are also certain operators to perform different kinds of mathematical functions like cos, sin, tan, log, pow etc

In Koala there are also certain operators used to perform advanced mathematical operations like derivation, mean, standard derivation, integration etc

There are also some design oriented functions available in Koala as well like threshold, trigger, sample etc

There are different constants related to electrical and mathematical.

Now in Koala there is powerful and user-friendly editor called Equation Editor is used to integrate all such kind of function and operators for different functions.

In Koala there are also different Library function named as Koala Library. In Koala different kinds of functions related to read and write are stored in Koala Library.

There is another feature of Koala that it also runs on different kinds of Unix platforms like SunOS04, Sun Solaris X86, Sun Solaris, Linux ELF and DEC OSF4.

4 From objected-oriented Programming to COM

It is very common to use different programming languages now. Now the world of technology has been divided into two parts due to programming languages, one is the original data and the second one is the different operations performed on that data. Normally data is static unless any kind of operation changed its nature. There are different methods and operations performed on the data that have no lasting state, but they are very helpful in their use to affect the nature of data. Now here we describe only two main language concepts like object oriented Programming and Component Programming. There was a language developed in 1967 by Ole-Johan Dahl and Kristen Nygaard considered as the first language having the concepts of Object Oriented language. 4.1 Object Oriented Programming

Object Oriented Programming normally condensed as OOP. There are different programming languages based on Object Oriented concepts. OOP was started at the end of 1960s just to cover some crisis related to different softwares. The basic idea in OOP is to design the computer in such a way that it looks like a collection of individual units and different objects as well which have some affects on each other. As there are different objects in a computer program which have certain characteristics like receiving messages, then process on data according to the situation and also to contact other objects by sending messages. There are also certain mistakes in OOP which are made by different programmers. Some of them are described below [7]

Classes and Roles

Data types and interfaces

Levels of abstractions

Policy and mechanism

Application and platform

Relation between uses and is-allowed-to-use

Run-time and compile-time

Aggregation and inheritance

Function application and message passing

Concept of analysis and designing of classes

Interface and implementation

Levels of details

4.2 What is a Component?

Component is a part of software that can be reused and it is in binary form. There is another property of the component that it can be used by other components as well. To develop a software component that is binary-compatible, COM is used as the main stipulation for that software. Actually COM is not a language but it serve as a compiler. COM can be build in any kind of language, in the mean while it allows the developers to build such components that can correspond to each other without any hesitation. There are different examples of COM like ActiveX Components, EJBs and Beans. These different technologies are developed and implemented by Microsoft and Sun Microsystems as well. When there was no concept of .NET there was different method to use the COM, its objects have to be registered inside the registry of window. The main objective of this was to use the objects by client programmers. [8]

4.3 Component Object Model (COM)

Component Object Model is a framework of Microsoft. Com is used for developing and also to provide supporting to component objects in a program. It includes same facilities Broker Architecture (CORBA). There are also some other interfaces and programming tools included in COM like COM+, Distributed Component Object Model (DCOM) and ActiveX. For interaction of objects and to support remote object invocation COM provides a binary structure. COM enhance the concept of object Oriented Programming (OOP) by providing the facilities of encapsulation, polymorphism and reusability of software. Due to reusability reason COM has become a dominate language for developing reusable software. There are two main requirements which have to satisfy every COM interface. The first one is that a pointer of COM always points to an array which contains pointers of virtual function. Other one is about the inheritance of COM interface that it always inherits from an unknown interface. There are three methods to perform this inheritance like QueryInterface () use for the navigation of same object instances occurred in between interfaces, AddRef () is used for the incrementing of reference counts and last one is Release () used for the decrement of reference counts.

COM is very popular and common software component model used for desktop and server side applications. Today COM has been replaced by another new technology called .NET for same purposes. Generally speaking COM is more suitable for development of embedded systems. There is a very basic concept of COM is about its interface. It means that the interfaces have no concern with the components that use them and those who implement them. There is an Interface Definition Language (IDL) is used by COM to identify the object-oriented interface. Infect the interfaces are just like object-oriented due to a solid reason that the classes use their operations and then after invoking a reference is passed to a specific instance of the class. There is also a run-time format used to access the interface pointers. There is also a policy related to instantiation. The main advantage of such kind of policy is ensuring the facility to install different kinds of components can be installed at different times in a system. The use of interface nodes in COM can be described as shown in figure 7.0

Interface PointerMethod Code

Interface node

Instance Data

VTABLE

Figure 7.0 Format of Interface nodes

4.4 Comparing OOP and COM

There are certain main advantages of OOP, but the most important advantage is data encapsulation. It means that there is very close relation between items and procedures of data. There is another strong feature is inheritance in OOP. It means that we can derive an object from a general object which is similar to general. We can easily understand the concept of inheritance by an example i.e. [15]

Class M ( )

{

Public:

Integer s

}

Class N: public M

{

Public:

}

It is very clear that class N is inherited from Class M. Class N has no data member. Class N will inherit the same data member from class M because when a class is inherited from another class then it includes the whole data members of the class from which it is inherited. There is another advantage of OOP that it allows to create, maintain and modify the existing code in a program just like a new object created by the existing one by just a small change in existing one. For the development in graphical user interface there is a nice framework in OOP that is also used for code libraries. Now in these libraries it is possible to update and modify the components related to supplied software by different programmers. But there are certain other main advantages of OOP like [9]

Simplicity

Modularity

Modifiability

Extensibility

Maintainability

Re-usability

There are certain main advantages of COM. There is no need to build the complete application each time in COM. There is the facility to rebuild only single component. In COM development, in COM first of all component interface is developed, which shows the fact that everything work together. There are also some important principles of Component programming like [12]

Binary Compatibility

Version Control

Location Transparency

Component-based security

Difference between interface and implementation

Independency of language

Binary Compatibility

There are also certain main differences between component and object oriented programming like

In OOP we focus on relationship of classes and then a large binary executable is used to merge all the classes that are used. While in Component programming the main focus is on code modules that are interchangeable and also such modules work independently. It is possible to factor business logic in different kinds of fine-grained classes but if we compile all these classes once then the end result of the classes is monolithic binary code. If there are different source files and more than one developers effort on identical code base then they have to share those file. In OOP the concept of reusing is known as white box reuse. The main reason behind this is to know about every kind detail about the implementation of OOP application. While in Component-based applications the reusing process is called black box. The main objective of black box reuse is to access the existing component and we do not need to know about its internal implementation. Binary-compatible interface is used as the basic unit of the component based programming. But in OOP object is used instead of interface. Similarly object is the basic unit used for reusing while in component based programming interface is used as basic unit for reusing. There is another difference between OOP and component based programming is the language independency. Like in component based programming there is no need to contact client in developing the server which is not possible in OOP [12]. There is an important thing that it is not possible to define OOP, Modular Programming and CBSE without storm. There are different definitions are available for each other but some of these available definitions are similar to each other and also oppose each other as well. Modular programming means that we break our software system into different parts as it is performed in CBSE. We can say that modular programming is a subset of CBSE. It means that CBSE is a type of Modular programming, but there are some extra qualities to be found in that form. OOP is also an extended form of modular programming which is pretty similar to CBSE. But in mean time there are some different features in OOP than CBSE even if they are similar in definitions. There are certain concepts of OOP which leads it to be a Modular programming like inheritance, encapsulation and polymorphism. [14]5 Component Based Embedded Systems

It has become a true factor that embedded systems are facing a lot of problems now, the reason behind this issue is just due to cost of hardware and need for different products. The example of such component based embedded systems are smart cell phones, PDAs and different devices related to home or industrial requirements. To solve such a problem it is necessary to develop such efficient systems to overcome these problems in very short time. Even now in such an advanced environment there are such systems which are still developed by assembler or using C language. Now there are such embedded systems which are platform dependent, such systems are difficult to upgrade port and customize. There is another drawback of these systems that they are not reusable. But component technology provides the facilities to develop such a natural units for reuse.

5.1 Framework for Component-Based Embedded Systems

A framework is a combination of different things like constraints which are related to components and also among their relations to each other. But there are also some good feature obtained from those constraints included in a framework. Before identifying development platform for developing component-based embedded systems, it is necessary to identify the whole transportation for different components. It is just because of a reason that component is used as the basic unit in component-based embedded systems.

Now in the market different languages have been developed which use different techniques like Visual basic uses Visual Basic Control which are known as VBX and Java beans are used in Java. To make the development of application easier there are different tools to share and distribute the application. But there are special underlying services which are used by all of those approaches by providing communication and coordination which is necessary in the development process of the application. The communication among the components is possible through Plumbing which is the infrastructure of components. As there are different technologies have been developed but there are three of them have become standard which are OMGs CORBA, Microsofts Component Object Model (COM) and Distributed COM (DCOM). There is also another knows as Suns JavaBeans and Enterprise JavaBeans. It is mentioned that Koala Model is another technology used for developing different embedded systems now.

6 Component-Based Software Engineering

Now to describe the quality assurance of component-based embedded systems there is a model. It is a true factor that the process to develop the simple system is very different from embedded system. So the QA Model should describe the both Components involved in the development and the whole system. Now there are certain standards available which are used to control different activities related to the Quality of the whole development process of the software, in such systems there are ISO9001 and CMM are well known. The QA model can be described as in figure 6.0.

Figure 6.0 A Quality Assurance Model for both Embedded System and Components

Now in QA Model there are certain important aspects related to the whole development process of a component-based embedded system. [6]

6.1 Component Requirement Analysis

Requirement analysis process of a component describes the different aspects related to the documentation, understanding, validating and also the management of the whole process. The main objective to design the requirement analysis is concerned to find the required requirements to develop an embedded system. The requirement analysis process can be described in a figure 6.1.

Figure 6.1 Overview of Requirement Analysis process

6.2 Component Development

Now the time to implement the whole requirements gathered during the requirement Analysis as described in figure. The main purpose of the component development process is to the final product and interfaces. It is necessary that component development should help to satisfy the results according to the requirement. An embedded system consists of both types of components i.e. Hardware and Software the whole process is described in figure 6.2.

Figure 6.2 Overview of Component Development process

6.3 Certification of Component

There are certain features involved in the process of certification of a component i.e. Component outsourcing, Component Selection and Component Testing. The main purpose of certification to test either the components involved in the system meet the requirements or not as described in the figure 6.3.

Figure 6.3 Overview of Component Certification process

6.4 Customization of Components

Now after the certification of components involved in the development of embedded systems, the next step is to customize the components which involved certain important aspects. The requirements have been updated so that the components are modified according to the requirements. Then there are some important changes in development just to make the components able to run on the platform of embedded system. Now as there are certain components which involved can increase the quality and performance are upgraded. So we can say that the main purpose of Customization is to make the components able to run in the embedded environment as describes in the figure 6.4.

Figure 6.4 Overview of Component Customization process

6.5 Designing System Architecture

In the designing phase the architecture of an embedded system which is component based is designed by evaluating and selecting different components involved in the designing process. The main objective of designing the architecture is to gather the requirements, clear the requirements of the system, after finding the requirements we have to choose the suitable architecture for the system and finally after all these details we think about the implementation requirements like language for programming, platform etc The whole process of designing the architecture can be describes as shown in figure 6.5.

Figure 6.5 Overview of Component Designing Architecture process

6.6 Integration of the System

Now in this process the whole selected components are assembled into a final system according the architecture of the embedded system. The main objective of integration is to get the final system as described in the figure 6.6.

Figure 6.6 Overview of Component Integration process

6.7 Testing of System

There are certain important aspects related to the testing of the system like system should satisfied the specified requirements and also mention the defects in the system and also correct those defects in the implementation phase of the system as described in the figure 6.7.

Figure 6.7 Overview of Component Testing process

6.8 Maintenance of System

The main purpose after designing the complete system, provide some services and some activities related to the maintenance. It would be beneficial to use the system after the delivery. The whole process can be described as in figure 6.8.

Figure 6.8 Overview of Component Maintenance process

6.9 Quality Assurance for Component-Based Embedded Systems

There are different issues related to the quality assurance which could be described as

6.9.1 Life Cycle

Since the development process of an embedded system includes the selection of different components and after that those components are assembled together instead of programming the whole system from graze. So it is clear that the life cycle of traditional embedded system software is different from component-based embedded system.

However the overall life cycle of component-based embedded software can be described as [6]

1. Requirements Analysis.

2. Selection, construction, analysis and evaluation of embedded software architecture.

3. Customization and Identification of components

4. Embedded system integration.

5. Testing of Embedded System.

6. Maintenance of Software.

6.9.2 Quality Characteristics of Components

There is a lot of work has been done on the development of component-based embedded software. Even then there are two main questions related to the development of such kind of embedded systems.

The first question is related to the quality i.e. how can we certify the quality of different components using in the development process of a component-based embedded system.

The second question is related to the overall system developed by different components.

To overcome these two questions the system must have some extra qualities like the system should be promoted to describe the whole quality control related to different components and the system as well. To know about the size there should be metrics. These metrics are also used to measure some other things related to the components and whole system as well like complexity, reliability and reusability. To know about different components and systems which are already existed there are different tools are used but these tools should be decided first. It is very necessary to know that how we can find the quality of a component in order to judge the component. But now after some research on quality characteristics related to components and the whole system as well, it is calculated that these are few like Functionality, Usability, Reliability, Testability, Interface and Maintainability.

As it is mentioned that there should be some metrics to assure the quality of components, these metrics should have some qualities i.e.

Size

There are certain factors related to the cost i.e. it covers reuse cost and quality. Now it is expected that the size could be small or large. If the size is small then it is related to cost and if it too big then it is related to quality.

Complexity

It has also the facts related to cost and quality. A simple component is not useful to use for reuse but if it is too much complex then is has the fact on quality.

Reuse Frequency

If a component is used in such a huge numbers then it affects the component features.

Reliability

It concerns with certain factors relates to failure-free.

7 Conclusion

Now its very easy to say that embedded systems are very important to compete the requirements of current era. And there are different components used to develop the embedded systems. Now there are different CPUs are used due to certain important functionalities of the embedded systems. The effort to develop the embedded systems started in 1960s. The first mass-produced embedded system launched in 1961. The embedded systems are computing devices controlled without any kind of key board or mouse. Real time systems are such systems to have the ability to meet the requirement within the required time under any kind of circumstances. There are a lot of things involve in Koala Components like interface, binding and bind time, diversity interfaces and product line architecture. Koala has some important features like rapid development. There are also some important features like Meta-Software-Hspice, Start-Hspice, and Smart-Hspice etc There are also some features related to different functions like logical, arithmetic etc There is a complete life cycle related to the development of embedded systems. So now it has become a true factor that Embedded Systems have become a important part of our lives in order to save the time. 8 References[1] Introduction of Real-Time Embedded System Design, http://people.cs.vt.edu/~cameron/cs4504/quan.pdf#search=%22Introduction%20of%20Real-Time%20Embedded%20System%20Design%22, (09-09-2006)

[2] Gang Quan, Introduction of Real-Time Embedded System Design, http://web.cecs.pdx.edu/~mperkows/temp/real-time-embedded-systems.pdf#search=%22Introduction%20of%20Real-Time%20Embedded%20System%20Design%22[3] Embedded system overview, http://en.wikipedia.org/wiki/Embedded_systems

[4] Sandeep Agrawal, Pankaj Bhatt. Real-time Embedded Software Systems An Introduction, August 2001.[5] Ivica Crnkovic, Component-based approach for embedded systems, Mlardalen University, Department of Computer Science and Engineering Sweden.

[6] Xia Cai, Michael R. Lyu, and Kam-Fai Wong. Component-Based Embedded Software Engineering: Development Framework, Quality Assurance and A Generic Assessment Environment, International Journal of Software Engineering and Knowledge Engineering Vol. 12, No. 2 (2002) 107.

[7] Object-oriented programming, http://en.wikipedia.org/wiki/Object-oriented_prog Component Programming in Dotnet ramming#Fundamental_concepts, (30-12-2006).[8] Component Programming in Dotnet, http://www.csharphelp.com/archives/archive270.html[9] Object Oriented Basic Concepts and Advantages, http://eprints.ecs.soton.ac.uk/857/03/html/node3.html[10] Rob van Ommering, Frank van der Linden, Jeff Kramer and Jeff Magee, London, The Koala Component Model for Consumer Electronics Software,

[11] Koala, http://www.eleceng.adelaide.edu.au/Koala/ (19-09-2006)

[12] Juval Lw, Programming .Net Components, Pblish By OReilly. [13] Ivica Crnkovic & Magnus larsson, Building reliable Component-based Software Systems, 1-58053-327-2.[14] Component-Based Software Engineering for Consumer Electronics,

http://www.nexwave-solutions.fr/frontend/whitepapers/CBSE_for_Consumer_Electronics(1).pdf.[15] Randy Charles Morin, OOP Concepts by Example, http://www.kbcafe.com/articles/OOP.Concepts.pdf,

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