1. Page 1 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Chapter 9 Component Composition and Integration

2. Page 2 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Overview qIntroduction qComponent integration qFrom integration to composition qSummary

3. Page 3 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Introduction Component integration  Component composition q Component composition l Determining the properties of assemblies in order to check their run-time compatibility, l Reaches further than integration. l Assemblies must be designed in such a way that they can live in a variety of contexts. l Determine how an assembly will affect the systems in which it is used and also how it is affected by these systems

4. Page 4 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Component Integration q Integration mismatches have, to a large degree, been ameliorated by the introduction of component models such as EJB, CORBA, and COM. qComponent models provide standards for components and a framework into which components can be plugged.

5. Page 5 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration From Integration to Composition q Integration mismatch encountered by Garlan et al., l Prevented them from plugging components together because of the use of different data formats. q The Compressing Proxy l Designed to improve performance of Web browsers through the transparent compression and decompression of transmitted data. l The mismatch allowed the proxy to deadlock.

6. Page 6 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration The Compressing Proxy Filter Pseudo Filter (Adaptor) gzip 1 23 4 Compressing Proxy Process Component Channel Function call interface UNIX pipe interface

7. Page 7 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Requirements q This is not a mismatch of components, rather one with the requirements of the system. l If the requirements are changed to restrict transmission to small enough files, the potential for deadlock disappears. q Analysis of the assumptions components make about the context in which they are to be used can help prevent design errors and result in building the right product faster.

8. Page 8 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Analysis of Assumptions “Architectural mismatch stems from mismatched assumptions a reusable part makes about the structure of the system it is to be part of. These assumptions often conflict with the assumptions of other parts and are almost always implicit, making them extremely difficult to analyze before building the system.”

9. Page 9 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Predictable Assembly q Assemblies can be made explicitly available to support hierarchical system composition. q Informally, compositional reasoning posits that: l IF we know something about the properties of two components, c1 and c2, l THEN we can define a reasoning function f: l SUCH THAT f(c1, c2) yields a property of an assembly comprising c1 and c2.

10. Page 10 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Achieving a Predictable Assembly q To begin, we suggest that three interlocking questions must be answered: l What types of system quality attributes are developers interested in predicting? l What types of analysis techniques support reasoning about these quality attributes, and what component property values do they require as input parameters? l How are these component properties specified, measured, and certified?

11. Page 11 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Prediction-enabled Component Technology q A prediction-enabled component technology (PECT) approach is based on two fundamental premises: l That system quality attributes are emergent properties that are associated with patterns of interaction among components, and, l That software component technology provides a means of enforcing predefined and designed interaction patterns, thus facilitating the achievement of system quality attributes by construction. l A prediction-enabled component technology consists of a component model and an associated analysis model.

12. Page 12 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Prediction-enabled Component Technologies Component Model Analysis Model Component Model Analysis Model assumptions interpretation PECT not connected specializes influences

13. Page 13 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Component Certification q Trusted computer security evaluation criteria (TCSEC) q Common criteria l The national security agency (NSA) l National institute of standards and technology (NIST) q The trusted components initiative (TCI) l Use of pre/post conditions on APIs (application programming interfaces)

14. Page 14 Building Reliable Component-based Systems Chapter 9 - Component Composition and Integration Summary q Component l Integration l Composition q Prediction-enabled component technologies l Software architecture-based analysis, l Component certification, l Architectural style q Produce component models that are enhanced to support reasoning about both the functional and extra- functional properties of software systems composed of components.