In the framework of the business cycle. Designers have designed the architecture and • compiled the document. The task now is to discuss how to assess and analyze the framework to ensure that the framework meets the requirements, be able to function properly. This is the focus of Part III, we first answered some basic questions about • assessment framework - the reason, time, costs, benefits, skills, within the plan, unplanned, front view conditions and results.
the reason
• most important fact about the system architecture is an important attribute of the system itself can be learned by understanding architecture - even if the system does not yet exist. Designer to develop design decisions that will have a downstream impact on the systems they build, these effects are enough knowable and predictable. If you do not design decisions is the case then, the design architecture process is almost toss like son: We just randomly chose a frame and then build the system based on this architecture, meat dish to see whether the system has the desired Li of: If not, return so far as to Zhuo new design. However, the framework is not cooking, we know we can do better than a random guess.
Designers generally know the impact of their design decisions that would result. As seen in Chapter 5 In particular, we can use the framework and the tactical mode of the system using this architecture having certain known properties. Therefore, the design choices (ie architecture) can be analyzed. Given a framework, we can infer some attributes of the system, even if the system has not built up.
Why play on the framework to evaluate? Because a lot of Shi feeling rely on the framework, and because we were able to evaluate the framework. Efficient methods for the assessment of a candidate architecture it became acceptable plan before the project - can have a huge economic value, with repeatable, structured process occurs (such as the undertaking of ATAM in Chapter 11 tells) , can provide a framework to assess the relative low cost of risk portability. Architecture must play to ensure that the framework is to meet the needs of both should be evaluated in the framework of each development method based on architecture in.
During the life of the software as much as possible to assess the quality is almost always cost-effective. If the problem is caught early, they are easy to correct - changing requirements, design specifications or juice are necessary. Not only focus on the latter part of the project software quality, pay attention to it at the outset, namely in the development of quality software design decisions to consider. Before carrying out a comprehensive development in the design phase of the design assessment of the candidate's project is the most favorable. "
However, the framework can be evaluated on a number of points in the life of the system. If the framework is still in its early days, the decision can be assessed or are being considered in the decisions that have been made. You can choose in the framework programs. If before the framework has been completed or nearing completion, it can be put to a long expensive development project on the framework for verification. Of being revised, porting, integration with other systems or system architecture early to assess other major upgrade is meaningful. Finally, the assessment framework is also an excellent discovery tool: staff development projects usually need to understand how the system inherited (or whether) to meet the demand for quality properties.
In addition, when the purchase will have a very long lifetime of large software systems, procurement organizations to understand the underlying system architecture candidate is heavy playing. This makes their suitability assessment accounts for possible based on the importance of quality attributes.
You can also choose between two competing frameworks by assessing: to both evaluate to see which framework to better meet the need to "good architecture" standard dishes.
cost
Cost evaluation is to assess the needs of infants and participants for their time. AT & T to require at least 700 days of the project was about 300 times the entire scope of the assessment framework, it is reported that, according to the estimates of individual project managers, the average cost review for 70 days. Based on the assessment of ATAM takes about 36 days. 'If your organization uses to assess a standard unit, then you must support it costs time and training members included.
income
For review frame 6 has the following advantages:
(1) Financial .. at AT & T, each project managers have reported savings were achieved assessment framework. Experience in the assessment of the framework within eight years shows that a comprehensive framework to assess the average cost savings of 10%. This shows that for 700 days or longer projects, accounting for comment by saving 70 days.
Other organizations have not announced such a convincing quantitative data, but there are children consulting firm reported that above 80% of the work they are doing repeat business. Its customers have fully recognized the value of the assessment. Willing to pay the extra money to be evaluated.
There are many Anecdotal customer to evaluate the framework in order to achieve cost savings. After a large company conducting the assessment, found the company to be purchased framework of a global information system does not provide the desired system of Li, thus avoiding millions of dollars in procurement. After the electronic funds transfer system for early architecture analysis found that the system can only transfer $ 50 billion per night, which is only half the capacity of the plastic. After a retail system early assessment found that there are performance issues orders. Peak period of the system, but how much hardware use all Wufajiejue, thus preventing the emergence of a major business failure, there are many like Shi love.
There are supposed to be, but not for event architecture assessment. To rewrite customer billing system is expected to play two-year period, but seven years later, the system has been re-achieved three times. The system has never had to meet the performance and computing power of the latest version of the CPU used was 60 times the original prototype version. In another large-scale project on relational database systems, the performance problems that occur mainly because of the development of the design decisions made it impossible for integration testing. After the investment of $ 20 million, the project was canceled.
(2) forced to prepare for the review. Description focused framework to assess the reviewers and asked them to express before the assessment framework, which means that the reviewers must be compiled documentation system architecture. Many systems do not - all a developer can understand architecture. Existing architecture description either too simple: either too complicated (and more common), there may be thousands of pages. And, for the assumption of certain elements, developers often misleading. In preparation for the assessment process will reveal a lot of problems.
(3) the basic principles of capture. Architecture assessment is usually focused on a few specific aspects of some specific issues need to be answered. Answering these questions usually 耑 to explain the basic principles and design choices. In the late period of life, basic design principles of a compiled document is very important, because it can be modified accordingly assessed the meaning of. In software development, system development after the completion of the basic principles of the capture is one of the tasks difficult to complete. Capture the basic principles (provided in the framework of evaluation) so as to have the valuable information for future use.
(4) found in the framework of the existing problems in the early detection, identify problems and more drought, less the cost of fixing these problems during the lifetime. Problems can include a reasonable assessment found that the framework (or costly) demands, as well as potential performance problems downstream problems associated with the modification. E.g. application evaluation system architecture modified scene may reveal portability and scalability problems. Assessment framework in this way can provide soap product capabilities and limitations of insight.
(5) validation requirements. Check the framework of the discussions and meet their needs can discuss on demand. The result is more understanding of the needs of Qing Chu, usually able to know the priority needs. When not considering early design decisions, create demand usually leads to system properties conflicting. We usually play seeking to achieve high performance, security, fault tolerance, and low cost, but these properties are difficult to achieve, and usually can not be achieved at the same time. Architecture assessment reveals the conflicts and trade-offs, we can negotiate the solution in the framework of its assessment.
(6) improved framework. Organization reports assess the framework of the development process, said the quality of its evaluation framework has been improved. Development organizations are expected to be proposed by the issue, the arguments will be presented and prepared a document assessing the demand of playing. They wanted very much to have the best performance in the assessment. After evaluating framework to assess not only get a better framework, but also before the full assessment of the case. With the passage of time the ceremony, the organization will cultivate a culture to promote good architecture design.
All in all, the quality can be improved by the framework to assess, control costs and reduce risk budget, the framework is a framework for all technology decisions, and therefore the cost and quality of its products has a very large eagle ring. Architecture assessments do not guarantee high quality or low-cost wood, but it points out the area at risk "test or quality documentation and coding system these factors also affect the final cost and quality.
skill
ATAM and CBAM next two chapters discuss methods of questioning techniques are examples of. Both methods use scenarios on how to ask questions in the assessment framework to respond to various situations. Other questioning techniques include a checklist or questionnaire. When evaluating the department repeatedly encountering the same kind of system, these are effective, and each time the same kind of probe is appropriate. All questioning techniques are basically dependent on thinking tests to discover the extent of the framework for its mandate.
Supplementary questioning techniques is a measure of skill, it relies on a quantitative measure for certain categories. The skills - one example is the architecture metrics. Metric coupling frame which its cohesion and depth of inheritance hierarchy module can be draw some of the obtained results for the system of the modification. Similarly, construct, or analog prototype, and then subjected to measurement in order to know the quality attribute of interest (here means running quality attributes, such as performance or availability) also. Kinds metric techniques. In a sense, the answer to the answer than questioning techniques measure skills given given more specific DA is applied to the work products of these techniques can only issue we had in Jian. In other words, use when the measurement technique, there must already exist, it can be a measure of the work product. For questioning techniques, on a hypothetical framework can be well applied it, and can be applied early in the life cycle.
Planned or unplanned
Assessment can be zoned or juice in the unplanned. Planned assessment is considered to be the project development cycle - a normal part. It has been arranged in advance. Is an integral part of the work program and budget of the project and the expected follow-up. Assessment of unplanned is unanticipated, usually because there is a serious problem projects, need to take extreme measures to remedy previous work.
In the ideal case, within the program evaluation is considered an asset of the project. In the worst case, it is considered a departure from their project can not be seen as a technical assessment of the project members of the authority of the peach war, but rather as a validation of the project was originally direction. Planned assessment is forward-looking, accomplished by the assessment team.
For the project participants, the foreign program evaluation is more like - kind of torture, resources and time projects already very nervous but also out of resources and time to evaluate. Only when management believes that the project is likely to fail and need to be corrected with concurrency process, will conduct unscheduled assessments. Unplanned assessment is reactive, project members will feel very nervous, the person in charge of the Panel's important to note, do not make the event into mutual accusations between the team members.
Needless to say, within the planned assessment it is more desirable.
Pre-conditions
Successful assessment should deposit with the following attributes:
(1) expressed a clear framework goals and needs. Only for the specific quality of Li, it can be said that architecture is suitable or unsuitable. For applications may require a modification of it. Provide exceptional performance framework may be completely wrong ,, do not know the specific "good framework" standard framework to analyze if it is to begin a trip without a purpose. Sometimes (but in our experience, it is almost impossible), the standard is in the requirements specification Che established. More likely, come standard before the actual assessment or determine the actual assessment. Target defines the purpose of the assessment, it should be explicitly evaluated as part of the contract, which will be discussed subsequently.
(2) ,, controllable range in order to focus on assessment, should list a few clear goals. The target number should be a minimum of three to five months, you can not define a small number of high priority targets may mean that expectations for the assessment (and possibly system) is unrealistic.
(3) cost-effective. The initiator of the assessment should ensure that the assessment of benefits outweigh the costs. Assess the type we have described is suitable for medium-sized projects for small-scale projects may not cost-effective the.
(4) the availability of key personnel. Always make sure the designer or at least be able to talk authoritatively system architecture and design staff time involved in accounting for comment. This person (or who) should be able to quickly mainly Qing Xi told about motivation as well as some of architecture decisions related to architecture. For large systems. Each of the main components of designers playing to be involved in evaluation to ensure that the designer of system design idea indeed be reflected in more detail and reflected out. The designer should also be able to tell the behavior and properties of the component quality. For ATAM, the identification of stakeholders in the framework of the assessment and expressed them. Determine the assessment of clients and understand their evaluation and expectations is a fundamental activity.
(5) a competent assessment team,, in the ideal case, the software architecture assessment team within the company • separate entities. They must be notarized, objective and respected. The team must be evaluated by the people for the composition, in order to make the project staff will not assess the dishes as a waste of time, and the evaluation results are valued and recognized. It must include the well-known architecture and framework elements of people, by people with extensive experience in architecture-level design and evaluation of projects to lead different.
(6) to manage expectations. The success of the appraisal is essential that both sides expect to support the assessment of the organization are - to understand a consumer Chu. Qing Chu assessment should target, as a result, will review again and again (not reviewed) region, will take up much time and resources projects and the assessment results submitted to whom.
result
The assessment should produce a report describing issues of concern and support data. After the initial preparation of the report should be
In its assessment among all participants circulated to identify and correct any misunderstandings and deviations. Each part of the report associated to form the final report. In the ideal case, if the problem is not resolved, it should prioritize issues based on their potential impact on the project.
It should also be gathering information on the assessment process itself. According to the results of the assessment can be repeated instruction, training, systems development and architecture and improve the evaluation process. Costs and benefits should assess the information gathered. The best development managers from the where to get information about estimated earnings. Review the organization should keep information about the assessment. And use this information to improve future assessments, provide a cost / benefit summary for managers to review the organization.
This part of the total chapter 3 "ATAM (Chapter 11 covers) is a kind of structured method • architecture assessment. Risk List .CBAM can draw a frame does not meet its business objectives (Chapter 12 tells) by using this method is determine which method the risk of first address the most likely to be very large number of risk in a large system, found in. determine which risk Emirates to resolve is to eliminate the risk of income and modified architecture to reduce the cost of the risk will be Compare .CBAM provides the structure of a deal with the organizational and economic problems. Chapter 13 gives a case study. it describes a system to support the World Wide Web, as well as its evolution constitutes an example of how several cycles of ABC.
See further literature
These introductory content draws on "best industry practices recommended by the assessment framework" [Abowd96], according to the authors of the report is a series of seminars and other staff organizations working in SEI written. Nuisance eight companies and consulting organizations represented at these seminars.
Architecture assessment is based on a checklist or questionnaire design review is an active form, [Pamas 85b] This is described. Orange pole design review means that all parties involved in the assessment of the use of pre-prepared documents to answer specific questions thus play a role in orange pole. Assess the opposition or unstructured such assessments and the Jikuaizhuyi. In assessing Jihuizhuyi or unstructured, only asked to assess the people involved to report any unusual circumstances they may be found.
[Cusumano 95] using metrics to uncover likely to change places. [AT & T 93] recorded a wealth of experience in AT & T carried out the assessment framework.