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A summary of the research claims described in section 1. That is, it does not define criteria for evaluating the approach.
In this section, I define three specific research claims about the usefulness and practicality online essay writing service review of the approach and explain how they will be evaluated.
The approach is applicable to the concerns that arise in real-world architecture evolution projects. The approach proposed in this work defines a set of concepts for reasoning about architecture evolution as well as a set of specification languages for modeling these concepts. But it is not immediately clear that these concepts and specification languages are actually useful for capturing the concerns that arise in the real world.
It might be that the kinds of concerns we had in mind when we developed this approach are quite dissimilar from those that arise in actual architecture evolution projects, and that our approach is online essay writing service review ill suited to representing the evolution concerns that arise in practice.
To evaluate the applicability of our approach for modeling the concerns that arise in online essay writing service review real architecture evolution projects, I conducted two case studies at large software organizations, in which I gathered data on architecture evolution projects at the organizations and then attempted to construct evolution models using our approach. These case studies are described in chapters 4 and 5. Thus, part of ensuring the practicality of our approach is evaluating the computational complexity of carrying out the necessary analysis of the evolution graph. I focus on constraints 9 1 Introduction in particular because the question of the tractability of evaluation functions is a less interesting one, as I will explain at the beginning of chapter 3. Finally, it should be emphasized that these three research claims are by no means the only criteria by which our approach might be evaluated. On the contrary, there are a host of qualities that might be evaluated: the usability of the approach (which could be evaluated through user studies), whether using the approach leads to good evolution outcomes (which could be evaluated through professional grad school essay writers a controlled experiment), its scalability to very large projects (which could be evaluated through simulations), and others. But the three criteria described above—applicability, computational complexity, and implementability—provide a reasonable basis for evaluation. I will discuss directions for future work in section 8. Chapter 2 details the approach to architecture evolution modeling that I illustrated informally by example in section 1. Chapter 3 undertakes a theoretical study of the specification language used to define evolution path constraints, proving some results on the computational complexity of path constraint verification. Chapters 4 and 5 describe two case studies on architecture evolution. Chapter 6 describes our preliminary work on tool implementation and reflects on what conclusions can be drawn as to the implementability of our approach to architecture evolution modeling. Chapter 8 cheapest custom research papers concludes by summarizing the contributions of this thesis, identifying the limitations of our approach, and discussing directions for future work. In this chapter, 1 describe the technical basis of the approach. The goal of the architect, in this model, is to select the optimal path through this graph. These evolution paths can be constrained by means of evolution path constraints, discussed in section 2. How can we model the various evolution paths available to a software architect who is planning a large-scale evolution of a system? How can we model and enforce constraints about which evolution paths are appropriate or permissible? How can we facilitate analysis of evolution path quality in a way online essay writing service review that supports architects in making trade-offs among candidate evolution paths and selecting the optimal path?
How can we capture expertise about domains of software architecture evolution so that it can be later reused to inform future evolution planning?
Domain expertise about classes of architecture evolution can be captured by means of evolution styles, described in section 2.
There are two specially identified evolution states: the initial state, which captures the architecture of the system as it exists at the outset of the evolution, and the target state, which captures the architecture that the system is to attain by the end of the evolution. Between these two states are the transitional forms that the system may take on as it is evolved. Each evolution state contains a complete representation of the architecture of the system. There are, of course, a variety of approaches for representing software architectures. Architecture description languages provide a rigorous way of representing the structure of a software system. Our approach does impose one hard requirement: there must be a way of expressing and evaluating architectural constraints —predicates that may hold or fail to hold for a given software architecture. This requirement is important because evolution path constraints (see section 2. Thus, without a means of expressing architectural constraints, we cannot express evolution path constraints. Of course, the choice of architecture description language has implications for the kinds of analysis that are possible. An architecture description language that lacks a type system, for example, will obviously not permit reasoning about the types of architectural elements. Chapter 6 will examine some of these implementation issues. The bottom line, however, is that most conventional methods for architecture description are suitable for use with our approach.
But often it is useful to consider multiple architectural views. Documenting a software architecture completely often requires the use of multiple views.
This makes possible constraints and evaluation functions that make reference to multiple views. We could support such a constraint by including, say, a UML component diagram (representing a component-and-connector view of the architecture) and a UML deployment diagram (representing a deployment view) for each evolution state.
Finally, in addition to containing a complete architectural representation of the system (which may comprise multiple views), an evolution state may be annotated with a set of evolution state properties. These free-form properties may be used to supplement the evolution state with additional information as desired. For example, they could be used to demarcate specially distinguished evolution states such as release points (with a Boolean isRelease property), to indicate special attributes like deadlines by which transitions must occur (with a date-type property), to specify business values like the expected impact of a node on the market (perhaps with a property of some complex type), and so on. The structural changes of the operator are defined by means of transformations.
A transformation represents a basic structural change to an architectural model.
Thus, transformations are things like adding a component, deleting a port, renaming a connector, and modifying a property. These transformations are composed to describe the structural changes that are effected by the operator.
In the case of Acme, the transformations will be things like adding a component, deleting a port, renaming a connector, and modifying a property.
In the case of a UML deployment diagram, they will include deploying an artifact to a node and adding a communication path. We have developed an informal, pseudocode-like operator specification language that allows for straightforward expression and composition of transformations, which is best illustrated by example. Figure 1 contains a complete definition of a wrap- LegacyComponent evolution operator based on the evolution scenario online essay writing service review described in section 1. The transformations block of the operator composes a number of transformations necessary to define the effects of wrapping a legacy component in a wrapper thesis coaching service. Then, it detaches all the connectors attached to ports on the legacy component and reattaches them to ports on the wrapper.