KOALA, Robocop, KobrA, PECOS and Pin COMPONENT MODELS Aneta Vulgarakis

C[K]omponent Organizer and Linking Assistent KOALA component model C[K]omponent Organizer and Linking Assistent Developed and used by Philips for development of software in consumer electronics

KOALA – component definition Component is a unit of design, development and reuse Interact between the environment or other components ONLY through explicit interfaces Koala components are defined in its: IDL (interface definition language) CDL (component definition language) DDL (data definition language) Syntactically: KOALA components are defined in ADL-like language Semantically: KOALA components are units of computation and control connected together in an architecture C influenced syntaxes

KOALA – interface definition Interfaces are represented as squares with triangles The tip of the triangle represents the direction of the function call Two types of interfaces: provides interface = methods to access the component from outside requires interface Koala component may behave like a system by itself provides interface required

KOALA – component composition Repository for KOALA components is the KoalaModel Workspace Composition of components is only possible in the design phase Connect: Provides interfaces to requires interfaces; Provides interfaces to provides interfaces; Requires interfaces to requires interfaces. Combination of components is a composite component KOALA configuration is a list of components and a list of connectors between the components

KOALA – component composition (cont’d) Three kinds of connectors: Binding – connect requires interface of a component to a provides interface of the same type of another component - provides interfaces are wider than requires interfaces => possible evolution of components - adding new functionalities to a component and still compatible with former versions - represented as a line Glue code – connects requires interface of a component to a provides interface of a different type of another component - written in C or limited expression language within Koala - represented as “m” (for modules) Switch – special glue code that switches binding between components - chooses between provides interfaces of different components at run time - represented as a “switch” note

KOALA – component composition (cont’d) subcomponent module switch interface In deployment phase Koala components are compiled into a programming language and executed in the runtime environment of that language NO NEW COMPOSITION OF COMPONENT INSTANCES IS POSSIBLE!

KOALA – example Stopwatch device for counting down from a specific number e.g. 100 Stopwatch device comprises Countdown and Display component Interface of Countdown component specifies the signature of function ‘count’ which Countdown component implements Countdown component definition defines its provides interface ICount and its implementation ‘c_impl’

KOALA – example (cont’d)

KOALA – basic principles of CBSE Reusability –ok Composition possible only at design time The builder can retrieve (composite) components from the repository – reuse Substitutability – no ? subtyping: new versions of a component are backward compatible with old versions Use subtyping for achieving substitutability Component A can be replaced by component B if it is a B subtype of A HOWEVER there are no direct constructs for replacing components by other components in the Koala language Extensibility – ok- at design and compile time New components can be added Possible to create a new interface type that contains all the functions of the previous interface plus some additional ones at design time Composibility - not ideal Only possible at design phase

KOALA – summary Component is a unit of design, development and reuse Koala components are constructed as CDL files and deposited into repository KoalaModel Workspace In design phase Koala components are composed by method calls through connectors In deployment phase no new composition is possible => there is no assembler Koala components are compiled into C and executed in the rum-time environment of that language

Robocop component model Developed in Eindhoven University Variant of the Koala model

Robocop – the project Defines an open, CB architecture for the middleware layer of high-volume consumer electronics The architecture consists of: development and execution framework optional download and resource framework At development level the component is a collection of models and relationship between these models Allow system builders to reason about a-priori about systems composed from components At execution level there is a binary component model, which combines element of OMG,CORBA,COM and KOALA

Robocop – component definition Component is a set of models each providing information about the component Different types of models are possible such as: - functional model - non-functional model: describes timing, reliability, memory usage Components are logically subdivided in services (similar to public classes in OO language Services are instantiated in run-time and are logically equivalent to objects in OO programming Robocop Component Resource Model Simulation Model Documentation Executable Component Functional Model Source Code …

Robocop – interface definition Interface definitions are specified in an Interface Definition Language (IDL) – Robocop IDL (RIDL) Interfaces are defined separately from services => multiple services can provide implementation of the same interface Each service has a special management interface, service interface Service interface contains operations for obtaining provided services from the service and binding the required interface to the provided interface of another server

Robocop – interface definition (cont’d) Robocop convention: User of some functionality is called a client Provider is called a server For minimizing coupling between clients and servers: The functionality is encapsulated in services that expose their functionality through interfaces – provided interfaces Required interface and 3rd party binding – clients specify what they need but not who will provide it, this is responsibility of the 3rd party Multiple interfaces – supported from provided and required side

Robocop – component composition Components can be composed from several models The composition of components is called application Robocop framework can calculate system properties from composition of components During run-time a Robocop platform can execute a component that resides on the platform or request a component from the repository => possible dynamic binding of services required by a component to services provided by another component

Robocop– basic principles of CBSE Reusability - ok It is possible to use third party components and reuse old ones Substitutability – ? Extensibility – ok Add new functionality to the system at design time, compile time and run-time Composibility At design and deployment phase ???

Robocop – summary Component is a set of models each providing information about the component Components are logically subdivided in services Interface definitions are specified in an Robocop IDL (RIDL) Interfaces are defined separately from services => multiple services can provide implementation of the same interface Components can be composed from several models and the composition of components is called application

KobrA component model Komponentenbasierte Anwendungsentwicklung Supported by the German Ministry of Research and Technology (BMBF) - Variation of UML model driven representation of components-

KobrA – component and interface definition Component is a UML component Component specification = what it does Describes all the properties of components instances that are visible to other component instances Specification of a component is the interface of the component Two interfaces: Requires interface = imported, supplied or used interface Provides interface = supplied or server interface KobrA component may behave as a system by itself

KobrA – component vs. system Many approaches see component development and component assembly as different activities Development with components ≠ development of components In KobrA component development and assembly are the same thing => A system = a component + = + =

KobrA – example Bookstore which wishes to maintain a database of its book stock The bookstore sells its books by and Automatic Teller Machine (ATM) The specification of the bookstore component is:

KobrA – component composition KobrA components are composed by direct method calls only in the design phase Construction of KobrA components in a visual builder ex Visual UML Repository of KobrA components is a file system stores a set of UML diagrams not possible to form a composite component in KobrA, only system template Design Deployment Run-time Component life-cycle

KobrA – example of component composition New ATM component is constructed BookStore and Book components are retrieved from the repository Components ATM, BookStore and Book are composed by direct method calls to a book store system

KobrA – basic principles of CBSE Reusability - ok? depends on the understanding of a CM At design phase new components can be deposited in the repository and components can be retrieved from the repository MARMOT approach developed especially for embedded systems Substitutability – ? Extensibility – ? Composibility Only possible at design time but it is treated as a system template

KobrA – summary Component is a UML component Components are constructed as a component specification and deposited into the repository The repository is a file system which stores a set of UML diagrams Kobra components are composed by direct method calls into a system template No new composition is possible in the deployment phase => no assembler

PErvasive COmponent System PECOS component model PErvasive COmponent System Collaborative project between ABB Corporate Research Centre and academia

PECOS – component definition Component is a black box with ports The component has a name number of property bundles – used to store non-functional properties (e.g. WCET) set of ports defined behavior Ports are for data exchange between components Components are specified with CoCo language, which is developed within PECOS project CoCo specifies only the properties and ports of a component, but not its behaviour

PECOS – component definition (cont’d) Behavior is a function, procedure or an algorithm that reads and writes data available at its ports Three types of components: Passive components : - do not have their own thread of control - they are scheduled by it closest active ancestor Active components : - have their own thread of control - used for very fast or very slow activities such as hardware registers or writing to slow memory Event components : - have their own thread of control - execution of the behavior is triggered by event

PECOS – interface definition The interface is port based Connected ports represent the same shared variable Port is specified with: Unique name within a component type of data passed over the port range of values that can pass through the port direction of the port (in, out, inout) Ports can be only connected if they have same type and their directions are complementary (in port to out port) Components may have no input or output ports

PECOS – UML diagram showing the structure of a component UML Meta model of a component, defining relations between different types of components and properties characterizing a component

PECOS – component example Clock component may be specified in CoCo like: component Clock { properties { memsize=32; description=“This is my first clock.”; } output long msecs; This is a passive component, with 2 properties memsize and description and an output port msecs of type long

PECOS – component composition The composition is done at only at design time (no repository) Sub-components don’t have implementation at design time Components are composed by connectors that link their ports No new composition possible at deployment phase Design Deployment Run-time Component life-cycle

PECOS – component composition (cont’d) Connector describes data sharing between ports It is described by: Name Type List of ports that it connects Two types of components Leaf component – “black box” directly implemented in the host programming language Composite component – contains sub-components (not visible outside the composite component) connected with internal ports

PECOS – example component composition PECOS system called Device. There are four sub-components EventLoop component is an active component used to handle graphical events such as mouse click The system Device has no ports because it is the application to be run

PECOS – example component composition (cont’d)

PECOS – basic principles of CBSE Reusability ? no repository at design phase => components constructed from scratch at design phase the builder has to construct a complete system of components and their composition Composition of component instances is the same as in that of the components in the design phase can we make our own repository??? Substitutability – ? Extensibility – ? PECOS components contain non-functional properties (memory consumption, WCET…) extensible architecture at design time and compile time Composibility Possible at design phase only

PECOS – summary Components are defined in ADL-like language called CoCo and constructed in a programming environment such as Eclipse At design phase composite components are made by linking their ports with connectors No repository in PECOS Implementation is usually done in Java or C++ => run-time environment in deployment phase is that for Java or C++ Suitable for small, very resource constrained embedded systems

Pin component model

Pin – component definition Component is an architectural unit that specifies a stimulus-response behavior by set of ports (pins) Components are defined in CCL(Construction and Composition Language) Components is represented by: set of sink pins set of source pins and component’s behavior sink pins source pins

Pin – component interface Pins are interaction points between components Sink pins – used to receive communication (stimuli) Source pins – used to initiate communication (responses) with its environment Behavior of a component is described by parallel composition of its reactions to sink and source pins

Pin – component example Component AComp which is described with structural and behavior aspects in CCL Structurally it has: asynchronous sink pin – receive and two synchronous (unicast) source pins – send and publish Behaviorally it has a threaded mission, takes receive, send and publish as parameters

Pin – component composition Components can only interact through their pins Composition is done at design phase by connectors which link source pins of one component to sink pins of another one No repository In deployment phase components are executed in Pin run-time environment

Pin – component composition (cont’d) Two types of connectors: synchronous connector – connects one source pin of a component to one sink pin of another asynchronous connector – connects one source pin of a component to multiple sink pins of another Only components within the composite component (assembly) can interact with each other The pins of an assembly are connected with the pins of its components by assembly junction Two types of assembly junctions: Null junctions – connect components of same environment type Gateway junctions – connect components in different environments

Pin – basic principles of CBSE Reusability ? no repository at design phase => components constructed from scratch at design phase the builder has to construct a complete system of components and their composition Composition of component instances is the same as in that of the components in the design phase can we make our own repository??? Substitutability – ? Extensibility – ? Composibility Possible at design phase from scratch

Pin – summary Component is an architectural unit that specifies a stimulus-response behavior by set of ports (pins) Components are defined in CCL which is an ADL language Components composed with connectors that link source pins of one component to sink pins of another component No repository in Pin In deployment phase implementations are generated in CCL processor and components are executed in Pin run-time environment

References Rob Van Ommering, Frank van der Linden, Jeff Kramer and Jeff Magee; “The Koala Component Model for Consumer Electronics Software”, IEEE Computer, March 2000, p78-85 Johan Muskens, Otso Virtanen, Michel Chaudron and Ronan Mac Laverty; “Maintaining Terminal Integrity and Context-Aware Reconfiguration”, ECOOP 2004, Oslo, Norway, June 2004 Johan Muskens; “Managament of Component Based Embedded Software Systems”, December 2005 (not yet published) Hugh Maaskant; “ A Robust Component Model for Consumer Electronic Products”, Philips Research Book Series Volume3, p167-192

References (cont’d) Mikael Åkerholm and Johan Fredriksson; ”A Sample of Component Technologies for Embedded Systems”, Technical Report, MRTC, November, 2004 Kung-Kiu Lau and Zheng Wang; ”A Survey of Software Component Models”, (second edition) Pre-print CSPP-38, School of Computer Science, The University of Manchester, May 2006 Peter Müller, Christian Zeidler and Christian Stich; “PECOS – Pervasive Component Systems ”, Workshop on ”Open Source Technologie in der Automatisierungstechnik”, GMA Kongress 2001 Anders Möller, Mikael Åkerholm, Johan Fredriksson and Mikael Nolin; “Evaluation of Component Technologies with Respect to Industrial Requirements”, 30th EUROMICRO Conference (EUROMICRO'04) p56 - 63  

References (cont’d) Colin Atkinson, Joachim Bayer and Dirk Muthig; “Component Based Product Line Development: The KobrA Approach”, 1st International Software Product Line Conference, Pittsburgh, August. C. Atkinson, J. Bayer, O. Laitenberger and J. Zettel; “Component Based Software Engineering: The KobrA Approach”, 3rd International Workshop on Component-based Software Engineering, Limerick, Ireland. Colin Atkinson, Barbara Paech, Jens Reinhold and Torsten Sander; “Developing and Applying Component-Based Model-Driven Architectures in KobrA”, Proceedings. Fifth IEEE International Enterprise Distributed Object Computing Conference, 2001. EDOC '01.