Abstract
QoS management is one important concern in the design of real-time systems. Component-based technology is a relevant approach to complex system development and to allow a smooth integration of software from different vendors. QoS management is an adequate means to provide a predictable quality to end users. We will bring together competencies in component-based design for hard and adaptive real-time systems, to produce advances that would be difficult to achieve without all three.

To achieve its aims, this activity requires competencies in component models, middleware, networking infrastructures.

Baseline

QoS concepts are starting to appear in component standards, but are far from mature. Partners in this JPRA have expertise in different aspects necessary for progress. An example is the request for proposal at the Object Management Group that is currently demanding solutions for the integration of some QoS facilities in CORBA Component Model.

There are a number of techniques and methods required for the industrial use of QoS aware components such as:

• Notations for the description of components models including functional and QoS (also know as non-functional” aspects. The integration of this information in the interfaces is of primary importance.
• Automatic generation of analysable models from the UML model.
• Composition mechanisms for determining whether it is feasible their interconnection and for deriving the non-functional characteristics of a group of connected components.
• Component frameworks to support the runtime composition of QoS aware components.

Previous Work

Some partners cooperated in the development of the OMG standard “UML profile for QoS and Fault Tolerance”, which was finally approved on May 2005.
The main result of this work was the concrete identification of the more concrete integration topics and the start of this work. This final job was done during a meeting that allowed the partners to know each other and discuss their interests. The identified integration topics were:

• Consistent alignment between the QoS modelling style of MARTE (with basis on Schedulability, Performance and Time) and that of the UML Profile for QoS and Fault Tolerance. The fist one is mainly related to time and performance aspects, while the second is more general, as it tries to provide means for specifying any other QoS characteristic. Partners involved: CEA, Inria, UPM.
• With respect to composability, the interest is focused upon the development of a contract model with well-founded semantics with respect to time and execution. This contract model will support (some) QoS characteristics. Partners involved: CEA, Inria, UC3M, UPM
• Finally, the support for the execution of QoS aware components requires components infrastructures with this support. UPM (QoS in the Robocop framework), UC3M, CEA and THALES (CCM based extensions) have done previous work on this topic. They have also proposed containers to simplify components development. The goal will be to
  interchange the approaches to try to get their particular merits and to propose new concepts for their future evolution.
  The work on these topics has started during the previous work period.

Problem Tackled in Year 2

The first issue is the identification of notations for the integrated description of functional and QoS properties in general component models. This will allow reasoning how a component or a set of them fulfils a certain set of requirements. The integration of non-functional aspects allows for ensuring this property along the development lifecycle, hopefully, in an automatic way. There are some attempts to define these notations, such as the OMG standards on UML profiles on “Real-Time and Embedded systems modelling and analysis (MARTE)”. “QoS and Fault Tolerance”. The next steps on relation with these topics are selection of some catalogs of QoS attributes of a QoS characteristic, in order to try to develop techniques for their modelling. With respect to this activity, two relevant characteristics are those related with time and safety. The work started during this year is to select a case study and QoS attributes, model them with different profiles or techniques and compare which is the most suitable in each case.

One of the utilities of these types of models is the possibility of generating automatically
models that can be used as input for analysis tools. The suitability of the previously mentioned profiles and attributes has been a subject of work for this period of time.

Another issue is to define how to compose QoS aware components. In this case, the connection of two components is only feasible if the provider includes the required operations with the proper functionality and QoS features. The common approach is the definition of a contract model where the specificities of the functions to be provided are determined and that serves as the basis for the evaluation of the feasibility of the composition and the resulted quality.

There are components infrastructures that provide the required support for the execution of components. However, there are no mature infrastructures supporting QoS aware components. In addition to the general functions, it is needed support for the negotiation between components, for finding a suitable provider, and with the system, for getting the resources required for its execution. There are some initial works towards these goals; such as extensions to CCM and Robocop component model that are a good starting point.

Current Results

The work has been aligned in three main activities:

• Specification of QoS properties using UML profiles and aspect-based approaches
• Generation of analysable models from the UML models
• QoS support in run-time components frameworks.
  INRIA has designed a technique to express the semantics of quality of service in a way compatible with classical functional and behavioural properties. The language for specifying quality of service relies on well-accepted and well-defined structures of the UML notation.
  Quality of Service properties (extra-functional issues, e.g. time, throughput, memory usage) are specified separately from the functional ones (classical types and pre/postconditions), using statecharts.

The transitions of these statecharts carry annotations that describe conditions of evolution as well as the side effects of this evolution on quality of service parameters. The composition of extra-functional statecharts with more classical, functional ones provides a specification that includes all aspects of the specification. QoS properties are thus handled using the separation of concern approach. QoS statecharts are in turn attached to software components, thereby extending the component specification with extra-functional properties.

The composition of extra-functional properties is managed by mapping extra-functional properties to functional ones on the components that implement these extra-functional properties. For instance, memory consumption of given components A and B is mapped to a memory abstraction component, which defines how A’s and B’s needs are satisfied and how they interact (e.g. whether the total amount required is below a threshold). The Inria technique leverages the concept of relativity of functionality: properties may be extra-functional under some points of view and purely functional under other points of view.

UPM has continued its work on the specification of QoS properties using the UML profile on “QoS and Fault tolerance”. It has developed a set of guidelines to make it easier its use. UPM has also worked on the UML modelling of safety and time properties. In particular, UPM has
worked on the modelling of safety properties is based on the safety evaluation processes from THALES ATM and EUROCONTROL. Then, it was defined a conceptual model that allows the representation of the safety properties, rules and methods. The next step was to develop annotations for UML that allows the description of the mentioned safety concepts. This work is being done and two approaches are being explored: use of the QoS and FT profile and using a newly created safety profile.

The main difficulties related with this work are the clear interpretation of the safety analysis process, the identification of the suitable elements in the conceptual model and the selection of the suitable UM L mechanisms for the modelling.

UPM has also experimented the generation of safety analysis models out of the UML annotated models. In particular, there are a couple of prototypes for fault-tree analysis and FMECA. The generated models can be used as input for commercial analysis tools (http://www.dit.upm.es/str, http://www.modelware-ist.org).

As a result of the ARTIST2 Workshop: "Beyond AUTOSAR" an effort was made at CEA, in collaboration with the Univesidad de Cantabria to address the identified necessity to perform evaluation of QoS and timing requirements of the component based applications. For this it is necessary to obtain as much as possible information of the components implementation from the manufacturers but preserving the intellectual properties involved. The idea is to ask the hardware/software components manufacturers to somehow partially "grey" their black boxes, requiring them to bring a timing behavioural model of the components that will be delivered, as soon as possible in the integration process. These models should be an abstraction of the functional behaviour implemented in the binary code, which will made explicit all the control flow paths for the worst case situations, the internal interactions, the mutual exclusive shared resources (critical sections), and the execution time consumed by each independent segment of code. Specific configuration and deployment services are required to be able to characterize and complete the models on the concrete platform to use. Once defined and integrated, these models will serve to evaluate response times as well as performance characteristics from a system wide viewpoint. The proposed strategy was presented in the 9th international Conference on Software Reuse 2006.

UPM and UC3M have worked on the improvement of the QoS management in the Robocop framework (http://www.hitech-projects.com/euprojects/space4u/index.htm,
http://www.dit.upm.es/str). The overall design has been modified in order to make it easier the handling of QoS properties. UPM has collaborated in the standardization process of the MPEG Multimedia Middleware (M3W). The QoS management APIs are part of the standard (http://www.chiariglione.org/mpeg/technologies/mpe-m3w/index.htm).

CEA and THALES are working on container extension mechanisms within the COMPARE project in order to add the QoS specification for container services by providing examples from our prototypes. They have also participated on the development of the OMG QoS4CCM specification that can be downloaded from the OMG page (http://www.omg.org/cgibin/doc?ptc/2006-04-15).

Keynotes, Workshops, Tutorials

Workshop : QoS-aware components
Paris (Saclay), 14 June 2006.
The objectives of the workshop are to present, discuss and integrate the approaches from the interested partners in the area of QoS-aware components. In particular, some of the relevant topics include:

• QoS support in components frameworks
• Description of QoS characteristics based on UML
• QoS contract models
• Integration of different real-time QoS properties on the different phases of the development

Publications Resulting from these Achievements

 [1] J. Fernández Briones, M. De Miguel, J. P. Silva, A. Alonso, Integration of Safety Analysis and Software Development Methods, 1st International Conference on System Safety Engineering IEE.
 [2] M. García Valls, I. Estévez Ayres, and P. Basanta Val, and Carlos Delgado-Kloos. CoSeRT: A Software Framework for Composing Service-Based Real-Time Applications. International Workshop on Enterprise and Networked Enterprises Interoperability (ENEI’2005). Lecture Notes in Computer Science. Nancy, France, September 5th, 2005
 [3] J.L. Medina, P. López, J.M. Drake, S. Gerard and F. Terrier. A Modeling Approach for the Verification of COTS Components-based Real-Time Systems. In the Workshop: Towards Off-the-Shelves Embedded Real-Time Systems, in the 9th International Conference on Software Reuse, Turin - Italy, 11 June 2006
 [4] Miguel de Miguel, Javier Fernández Briones, Juan Pedro Silva, Alejandro Alonso, Model Based Integration of Safety Analysis and Development, ISORC 2006.
 [5] Miguel A. de Miguel, Bernard Pauly, Thierry Person, Javier Fernandez, Model-Based Integration of Safety Analysis and Reliable Software Development, WORDS 2005.
 [6] S. Robert, A. Radermacher, V. Seignole, S. Gérard, V. Watine and F. Terrier, Enhancing Interaction Support in the CORBA Component Model.. In From Specification to Embedded Systems Application, pages 137-146, Manaus, Brazil. IFIP, August 2005.
 [7] Sylvain Robert, Ansgar Radermacher, Vincent Seignole, Sébastien Gérard, Virginie Watine, François Terrier, The CORBA Connector Model. In Fifth International Workshop on Software Engineering and Middleware (SEM 2005), Lisbon, Portugal. ACM, September 2005.
 [8] Juan Pedro Silva, Miguel de Miguel, Javier Fernández Briones, Alejandro Alonso. Safety Metrics for the Analysis of Software Architectures, Workshop on Visual Modeling for Software Intensive Systems 2005.

ARTIST2 Core Participants: Expertise and Roles

• Alejandro Alonso (UPM)
  QoS component infrastructures and notations for QoS specification.
• Jean-Marc Jezequel (INRIA)
  extra-functional modelling.
• François Terrier (CEA)
  QoS information in models.
• Jacques Pulou (FTR&D)
  QoS in component-based middleware.

Affiliated Participants: Expertise and Roles

• Laurent Pautet (ENST)
  real-time middleware, timed contract based behavioural typing, component-based adaptive services in mobile networks.
• Stefan van Baelen (K.U. Leuven)
  QoS specifications and negotiation mechanisms.
• Marisol García-Valls (U. Carlos III of Madrid)
  QoS component infrastructures, real-time middleware architectures.
• Virginie Watine (Thales)
  component-based middleware, Co-Chair of MARS group at OMG on CORBA, RTE, etc.

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