Differences

This shows you the differences between two versions of the page.

--- course_outline [2015/04/08 17:18] – jonathan
+++ course_outline [2015/06/24 17:53] (current) – jonathan
@@ Line 9: / Line 9: @@
 Software designers are experts at developing software products that are correct, robust, efficient and maintainable. Correctness is the ability of software products to perform according to specification. Robustness is the ability of a software system to react appropriately to abnormal conditions. Software is maintainable if it is well-designed according to the principles of abstraction, modularity, and information hiding. At the end of the course, students will be able to:
-. Describe software specifications via Design by Contract, including the use of preconditions, postconditions, class invariants, loop variants and invariants
+. **Specification**: Describe software specifications via Design by Contract, including the use of preconditions, postconditions, class invariants, loop variants and invariants
-. Implement specifications with designs that are correct, efficient and maintainable.
+. **Construction**: Implement specifications with designs that are correct, efficient and maintainable.
-. Develop systematic approaches to organizing, writing, testing and debugging software.
+. **Testing**: Develop systematic approaches to organizing, writing, testing and debugging software.
-. Develop insight into the process of moving from an ambiguous problem statement to a well-designed solution (analysis).
+. **Analysis**: Develop insight into the process of moving from an ambiguous problem statement to a well-designed solution.
-. Design software using appropriate abstractions, modularity, information hiding, and design patterns (design).
+. **Architecture**: Design software using appropriate abstractions, modularity, information hiding, and design patterns.
-. Develop facility in the use of an IDE for editing, organizing, writing, debugging, testing and documenting code including the use of BON/UML diagrams for documenting designs. Also the ability to deploy the software in an executable form.
+. **Tools**: Develop facility in the use of an IDE for editing, organizing, writing, debugging, testing and documenting code including the use of BON/UML diagrams for documenting designs. Also the ability to deploy the software in an executable form.
-. Develop the ability to write precise and concise software documentation that also describes the design decisions and why they were made.
+. **Documentation**: Develop the ability to write precise and concise software documentation that also describes the design decisions and why they were made.
+===Commentary===
+A design for a software product is the combination of its specification (to verify its safety and correctness) and a suitable architecture (for maintainability). A design that is not correct cannot be a good design. A design that does not have a suitable modular architecture is not a good design.
+===Eiffel==
+Why do we use the Eiffel method in this course? The worldview underlying the Eiffel method is to treat the whole process of software development as a continuum; unifying the concepts behind activities such as requirements, specification, design, implementation, verification, maintenance and evolution; and working to resolve the remaining differences, rather than magnifying them. Anyone who has worked in both specification and programming knows how similar the issues are. Formal specification languages look remarkably like programming languages; to be usable for significant applications they must meet the same challenges: defining a coherent type system, supporting abstraction, providing good syntax (clear to human readers and parsable by tools), specifying the semantics, offering modular structures, allowing evolution while ensuring compatibility. The same kinds of ideas, such as an object-oriented structure, help on both sides. Eiffel as a language is the notation that attempts to support this seamless, continuous process, providing tools to express both abstract specifications and detailed implementations. One of the principal arguments for this approach is that it supports change and reuse. If everything could be fixed from the start, maybe it could be acceptable to switch notations between specification and implementation. But in practice specifications change and programs change, and a seamless process relying on a single notation makes it possible to go back and forth between levels of abstraction without having to perform repeated translations between levels. [Quoted from [[https://bertrandmeyer.com/2014/12/07/lampsort|here]]]
 ==== Topics ====
@@ Line 144: / Line 149: @@
 === Slides 16 ===
-Correctness: Design by Contract and loop variants and invariants. Tolerant (involving defensive programming) and strict routines, depend on the strength of the preconditions.
+Correctness: (a) Hoare logic and (b) Design by Contract and loop variants and invariants. %%(c)%% **Tolerant** (involving defensive programming) and **Demanding** routines, depend on the strength of the preconditions. (d) The difference between **abstract algorithms** and their **program implementations**.
 [[https://bertrandmeyer.com/2014/12/07/
 lampsort/|Lampsort]]. Algorithms such as Quicksort are normally presented too close to implementation (e.g. as a recursive routine). But Quicksort is really a divide-and-conquer at the abstract level that can be refined to a recursive, iterative or concurrent implementation. Eiffel (and loop variants/invariants) can describe the more **abstract algorithm** rather than its too **detailed implementation**.
-The Eiffel method is almost the reverse: treating the whole
+The Eiffel method treats the whole
 process of software development as a continuum; unifying
 the concepts behind activities such as requirements,