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Software Engineering – The Software Process

Software Engineering – The Software Process. PRESCRIPTIVE MODELS Every software engineering organization should describe a unique set of framework activities for the software process(es) it adopts.

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Software Engineering – The Software Process

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  1. Software Engineering – The Software Process PRESCRIPTIVE MODELS Every software engineering organization should describe a unique set of framework activities for the software process(es) it adopts. It should populate each framework activity with a set of software engineering actions, and define ach action in terms of a task set that identifies the work (and work products) to be accomplished to meet the development goals. It should then ADAPT the resultant process model to accommodate the specific nature of each project, the people who will do the work, the environment. Regardless of the model, all models contain the following components: communication planning modeling construction deployment Which of these phases do you think is most difficult and in what situations?

  2. Software Engineering – The Software Process PROCESS MODELS What do you think the most popular process model is? Waterfall Incremental Evolutionary Component Based Formal

  3. Software Engineering – The Software Process PROCESS MODELS What do you think the most popular process model is? I would say that the “no process model” is the most popular.

  4. Software Engineering – The Software Process PROCESS MODELS – WATERFALL The “Classic Life Cycle”, The “Textbook Cycle” A systematic, sequential approach with the following steps: Customer Specification of Requirements (Communication) Planning (Estimating, Scheduling, Tracking) Modeling (Analysis and Design) Construction (Code and Test) Deployment (Delivery, Support, and Feedback) The book calls the first phase communication. I do not like this definition as communication must occur at all stages.

  5. Software Engineering – The Software Process PROCESS MODELS – WATERFALL When is the waterfall process model appropriate? In a purest sense, probably never. I have never worked on a project that follows a completely linear progression. However, the waterfall process is appropriate if followed in spirit if not the letter of the model in some situations: Well defined projects Projects with no technology risks Well defined domains Stable requirements

  6. Software Engineering – The Software Process PROCESS MODELS – WATERFALL Why is it difficult to follow? Hard to follow a strictly sequential path. Customers have difficulty stating ALL the requirements explicitly Customers business model changes during the course of developing the application Customers are required to have patience, since a working program is not available until very late in the process.

  7. Software Engineering – The Software Process PROCESS MODELS – INCREMENTAL PROCESS MODEL Even with well defined projects, a linear approach is often difficult. Additionally, sometimes a portion of the software needs to be delivered early. The incremental model combines elements of the waterfall model applied in an iterative fashion. Incremental model delivers an operational product with each increment. Works well for project resource management (staffing).

  8. Software Engineering – The Software Process PROCESS MODELS – INCREMENTAL PROCESS MODEL

  9. Software Engineering – The Software Process PROCESS MODELS – RAD MODEL RAPID APPLICATION DEVELOPMENT (RAD) Incremental software process that emphasizes a short development cycle. Highly efficient waterfall model in which rapid development is achieved by using component based construction. Requires well understood project scope. Same framework as waterfall: Customer Specification of Requirements (Communication) Planning (Estimating, Scheduling, Tracking) Modeling (Analysis and Design) Construction (Code and Test) Deployment (Integration, Delivery, Support, and Feedback Key difference is parallel development during Modeling and Construction. Also added to Deployment is an INTEGRATION phase.

  10. Software Engineering – The Software Process PROCESS MODELS – RAD MODEL

  11. Software Engineering – The Software Process PROCESS MODELS – RAD MODEL Usual development time is less than three months. Drawbacks: Large scalable projects, requires sufficient human resources Everyone must buy in to short term delivery Some systems can not be modularized easily Difficult when there are high technology risks Integration Risk (Not in the book, to me this is the largest concern.)

  12. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING Customers define general objectives , but does not identify the details. Often, the customer doesn’t know what they want the system to look like. Can be a stand alone process or integrated into other models. I prefer it to be integrated. A repeating cycle of the following steps include: Communication Quick Plan Modeling Quick Design Construction of Prototype Deployment & Feedback

  13. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING Depending upon the complexity I recommend a first pass with “Paper Prototypes”. “Paper” can be virtual with mockups of the application being developed in either a development environment like Visual Studio or even HTML. Second pass could be a semi functional application with no data connectivity. Third pass for the developers to try any unknown technical issues. Often good for these prototypes to be used for requirements gathering and to reduce technology risks. Best if the prototype is a throw-away. One good reason to develop your prototype in a different language/system than the final project

  14. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING Drawbacks: Customers like the prototype and want to place it in production. Developers forget the design decisions and their mistakes leak into the production system.

  15. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL – SPRIAL MODEL An evolutionary software model that couples the iterative nature of prototyping with the controlled and systematic aspects of the waterfall model. This is true, but with one addition: risk analysis. At each cycle through the spiral, milestones are achieved and risk is reevaluated.

  16. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL – SPRIAL MODEL

  17. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL Most developers lean towards evolutionary process models. They have inherent problems: Prototyping and similar evolutionary models are hard to plan, thus hard to estimate, thus hard to contract. How many cycles will there be? Speed of evolution is difficult to dictate Software processes should be focused on flexibility and extensibility rather than on high quality. Is the third statement true? Why is this a goal?

  18. Software Engineering – The Software Process PROCESS MODELS – EVOLUTIONARY PROCESS MODEL Most developers lean towards evolutionary process models. They have inherent problems: Prototyping and similar evolutionary models are hard to plan, thus hard to estimate, thus hard to contract. How many cycles will there be? Speed of evolution is difficult to dictate Software processes should be focused on flexibility and extensibility rather than on high quality. Is the third statement true? Why is this a goal? The concept behind it is that if software is late, the opportunity of it is lost.

  19. Software Engineering – The Software Process PROCESS MODELS – SPECIALIZED PROCESS MODEL COMPONENT-BASED DEVELOPMENT Commercial off-the-shelf software components, can be used when software is built. Process includes: Identification of candidate components Either object-oriented or procedural Consider integration issues Design a software architecture Integrate components Comprehensive testing Does anyone do this as a pure process model? More likely as part of another model. We all use pre-built components. i.e. Borland text editor, advanced data grid, Date/Time pickers, etc

  20. Software Engineering – The Software Process PROCESS MODELS – SPECIALIZED PROCESS MODEL FORMAL METHODS MODEL The Formal Methods Model encompasses a set of activities that leads to formal mathematical specification of computer software. In theory, the following is reduced when using formal methods: Ambiguity Incompleteness Inconsistency Do you agree?

  21. Software Engineering – The Software Process PROCESS MODELS – SPECIALIZED PROCESS MODEL FORMAL METHODS MODEL Drawbacks: The development of formal models is currently quite time consuming and expensive Few software developers have the background, thus extensive training is required. (is training viable? COBOL -> OOP) Difficult to use formal model to communicate with a non-technical customer. Forest and Trees. Useful for safety critical application or anywhere failure is highly costly.

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