Apply modeling Standards This is the am version of XPs Coding Standards practice. Apply patterns Gently This practice reflects the yagni principle to the effective application of patterns within your system, in conformance to xps practice of Simple design. Apply the right Artifact(s) This practice is not explicitly described by xp principles and practices although is very much aligned with xp philosophies of if you need it do it and using the most appropriate tool or technique for the job at hand. Collective ownership am has adopted XPs Collective ownership practice. Create several Models in Parallel This is a modeling-specific practice. Xp developers can clearly work on several models such as crc cards, acceptance test cases, and sketches if they choose to. Create simple content This is complementary xps Simple design practice that advises to keep your models as simple as possible. Depict Models Simply This is complementary xps Simple design practice that suggests that your models do not need to be fancy to be effective, perfect examples of which are crc cards and user stories.
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Because modeling is clearly a part of xp, see above, the potential exists for am to add value to an xp project. This assumes of course that there is possible to tailor am into xp, i believe it is and argue so below, and that you can do so without detracting from what currently exists within. In particular, xps practices of refactoring and test-first development clearly do a very good job of filling in for two critical goals promoting clean design and thinking through your design before writing code that are typically the associated with traditional modeling processes. My experience is that both refactoring and test-first development are complementary to am and arguably enablers of several am practices, as i argue below. In this section i explore the following issues:.1 The potential Fit Between am and xp a critical issue that must be addressed is how well am fits with. Table 1 lists the practices of am and either maps them to existing principles or practices of xp or discusses the potential fit of the am practice when it is not explicitly a part. Because xp was used as a foundation for am many of the practices map straight. However, because ams focus is on modeling several practices are clearly new, hence the potential for am to bring value to an xp project. Applicability of am practices on an xp project. Am practice fit With xp active stakeholder Participation This practice is simply a new take on XPs On-Site customer practice. Am uses the term project stakeholder in place of customer and focuses on the concept of their active participation, hence Active stakeholder Participation and not On-Site Stakeholder.
As I suggest in Agile documentation online a good rule of thumb to ensure that youre traveling light is that you shouldnt create a model or document until you actually need it creating either thing too early puts you at risk of wasting your time working. An important thing to understand about documentation on an xp project is that it is a business decision, not a technical one. This is consistent with AMs philosophy regarding documentation, discussed in Agile documentation. Jeffries says it best: If there is a need for a document, the customer should request the document in the same way that she would request a feature: with a story card. The team will estimate the cost of the document, and the customer may schedule it in any iteration she wishes. 1.3 xp and The uml see the article xp and the uml? Clearly the Wrong question to be Asking. Am should be tailored into an existing, full lifecycle methodology, in order to improve its approach to modeling.
What confuses many people regarding xp and documentation is that xp doesnt specify potential documents to create during development. This is unlike the reviews rup which suggests a slew of potential project artifacts. Instead, the year suggestion is to work together with your project stakeholders in an environment of rapid feedback and trust them to determine the things that they need, not just documents but any type of project enhancements. Once again, you need to have the courage to trust the people involved with the project. In the article Agile documentation I discuss a collection of documents that you may choose to create and provide advice for when to consider creating them. One of the greatest misunderstandings people have about xp regards concept of traveling light many people believe that it means you dont create any documentation, but nothing could be further from the truth. What traveling light actually means is that you create just enough models and documentation, too little or too much puts you at risk.
When you think about it, this makes a lot of sense. When you are learning something new do you prefer to read a bunch of documentation or do you look for source code samples? Many developers prefer to start at source code samples, and the test suite provides these samples. Second, xps focus on simplicity and practice of refactoring result in very clean and clear code. If the code is already easy to understand, why invest a lot of time writing documentation to help you to understand it? This applies to both internal and external documentation why add comments to code that is already clear and unambiguous? If the code isnt so, then refactor it to improve its quality or as a last resort write documentation. Even though some development environments make it easy to include documentation in your code, javas javadoc utility is such an example, you only want to invest in documentation when it makes sense to do so and not just because it is easy.
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Fifth, it implies that tunnel you should trust the team and give them control over their own destiny. This can be hard in many organizations. If the team is untrustworthy then you have a serious problem that needs to be dealt with, this is true regardless of whether they are following xp, or if they are trustworthy but your organizational culture doesnt allow you to act based on that trust. Another problem is that when you are an outsider to an xp team, when you havent been actively involved in the conversations and interactions that have replaced the need for documentation, that it appears that there isnt enough documentation. When this is the case, instead of forcing the team to write documentation instead invest the time to determine if they need the documentation that you believe is missing suggest the documentation to the team, and if there is an actual need for it then.
As Ron Jeffries likes to say, its called Extreme Programming not stupid programming. Finally, the most important implication for xp teams is that if you need documentation then write. The need for documentation on an xp project is reduced by several of its practices. First, because of test-first development and a focus on acceptance testing there is always a working test suite that shows that your system works and fulfills the requirements implemented to that point. For the developers, these tests act as significant documentation because it shows how the code actually works.
In fact, in the second edition he includes a mind map in the inside cover overviewing. The bottom line is that modeling is a fundamental aspect of xp, something that i explore in detail in this article. 1.2, documentation, happens, documentation is also an important part. Ron Jeffries offers the following advice: Outside your extreme programming project, you will probably need documentation: by all means, write. Inside your project, there is so much verbal communication that you may need very little else. Trust yourselves to know the difference.
There are several interesting implications of that statement. First and foremost, the xp community recognizes that documentation should be produced for people external to your team, people that am would term project stakeholders. Second, it points out that verbal communication between team members reduces the need for documentation within the team. This is the result of project team members being co-located, making communication easier, as well as aspects of xp such as pair Programming and Collective ownership that promote communication between developers. As I discuss in the article on Communication documentation is only one form of communication, one that is typically the least effective, that can be easily replaced by more effective techniques such as face-to-face communication. Third, it recognizes that sometimes you do in fact need internal documentation for your team. This is consistent with the advice presented in Extreme Programming Installed where the authors point out that information resulting from conversations with your project stakeholders regarding user stories are captured as additional documentation attached to the card. More on this in the section a closer look at the xp lifecycle. Fourth, it suggests that xp team members should know when documentation is required and be allowed to act accordingly.
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In this section I will set the record straight regarding the three most common issues concerning modeling and XP:.1, modeling is Part of xp, user stories are a fundamental aspect of xp and artifacts such as Class Responsibility collaborator (CRC) cards are common. User stories provide a high-level overview of the requirements for a system - they are reminders to have a conversation with your project stakeholders regarding their requirements - and are used to as a primary input into estimating and scheduling, and drive the development. Crc cards are used to explore structure, perhaps for conceptual modeling to understand the problem domain or for design to work through the structure of your software. User stories and crc cards are both models, see the. Artifacts for am article, so therefore modeling is clearly a part. Xp developers will also create sketches, often on a whiteboard or a piece of paper, whenever user stories and crc cards arent the best option. Extreme Programming Explained, the first book written about xp, kent Beck includes hand-drawn friend sketches of class diagrams and other free-form diagrams.
Many developers find themselves in less-than-ideal environments. Xp requires you to adopt practices that are often foreign to your current environment, pair programming and test-first development are new to most organizations, and sometimes these practices simply arent feasible to adopt. If you cannot adopt the practice of pair programming then xp isnt going to work for you, but instead of proclaiming that xp doesnt work in their environment many people will instead proclaim that xp doesnt work at all. The reality is that xp does in fact work in the right situations, it is just that your situation may not be one of the right ones. Too much focus on the word extreme. XPs name is both baisakhi one of its greatest strengths its greatest weaknesses. Because of the name when some people hear XPs advice to travel light, to reduce the amount of documentation that you create and maintain, that they instead translate it to create no documentation at all. Or theyll hear XPs advice to use simple modeling techniques such as user stories and, cRC cards and somehow translate that advice to you dont model at all.
the group/list. Someone will post something, which may not be accurate, and many people will accept it as official, particularly when they havent had an opportunity yet to try it out for themselves. Dont believe everything that you hear. Questionable sources of information regarding. Its often hard to determine the quality of published material, be it electronic or printed form. Sometimes honest mistakes are made, thats happened to me more than once, and sometimes people publish misleading information on purpose. When youre just learning a new subject you often cannot distinguish between high-quality sources of information and questionable ones. If you base your understanding on questionable sources it is very easy to get the wrong idea about. Difficulty seeing beyond their current environment.
Rational Unified Process (RUP) the topic of gps the article, agile modeling and the Unified Process. Table of Contents, setting the record straight. Am throughout the xp lifecycle, how do you make this work? Setting The record Straight, there are several common misconceptions that people seem to have regarding modeling on an xp project. The three most common misconceptions are that you dont model on an xp project, that you dont document on an xp project, or that if you do model your only options are the modeling artifacts of the uml. Ill address these misconceptions in turn in this section, but first I want to explore why they occur so that you can recognize other misconceptions when they arise. From what I can gather based on the conversations on the. Am mailing list the source of these misconceptions is often the result of one or more of the following: Second-hand knowledge.
Recommended reading: Robert Kirk, relativism and resume reality: a contemporary Introduction (Routledge, 1999 larry laudan, Science and Relativism: Some key controversies in the Philosophy of Science (Chicago, 1990 Ernest Gellner, relativism and the social Sciences (Cambridge, 1987 moral Relativism: a reader,. Moser and Thomas. Carson (Oxford, 2000 james Kellenberger, moral Relativism, moral diversity, and Human Relations (Penn State, 2001 richard Rorty, objectivity, relativism, and Truth (Cambridge, 1991 and Christopher Norris, Against Relativism: Philosophy of Science, deconstruction, and Critical Theory (Blackwell, 1997). Agile modeling (AM) is a practices-based software process whose scope is to describe how to model and document in an effective and agile manner. Am home page, i state that one of the goals of am is to address the issue of how to apply modeling techniques on software projects taking an agile approach such as eXtreme Programming (XP), dynamic Systems development Method (dsdm), and, scrum to name. Because the scope of xp is much greater than that of am, xp covers the full development lifecycle, it is a candidate "base process" into which the techniques of am may be tailored. Furthermore, although xp clearly includes modeling as part of its process it is not as explicit about how to do so as many developers would prefer. Hence an opportunity for. Luckily xp, like am, is also an agile practices-based methodology which makes the conceptual fit between the two methods much easier than between am and a process such as the.