![18
Functional Decomposition Technique
Dates back to “structured programming”
[now (non-OO) Web apps with PHP tool].
Start with: main (task/requirements) --> module.
Refine into sub-modules.
There are alternative decompositions.
19
Possible Decomposition of
(Student-Course Management App)
20
“Alternative” Decomposition/Composition
21
Relational Database Design
Most databases use relational technology.
Relations (tables):](https://image.slidesharecdn.com/thirdassignmentdescribein100200wordsanapplicationwith-221115171714-0f44e51a/85/Third-AssignmentDescribe-in-100-200-words-an-application-with-docx-10-320.jpg)
Third AssignmentDescribe in 100 – 200 words an application with .docx
- 1. Third Assignment Describe in 100 – 200 words an application with which you are familiar. This should be an application with which other students and the course instructor are likely to be familiar. An example would be Microsoft Word. Then, select one of the architectural design styles given in the presentation on Architectural Design. Explain why this style is appropriate for the application you described. Then apply this style to the application and explain the result in enough detail that your fellow students are likely to understand. Organization of your submission Third Assignment Your name Submission Date Application Description Style you have selected Why this style is appropriate for this application The application’s architecture using this style Explanation of this architecture (show how some common tasks for this application might be performed using this architecture) Grading Rubric Criterion Points Application description is well-organized 5 Style choice is one of the styles described 2 Style choice is effectively justified 8 Presented architecture uses the selected style 3
- 2. Presented architecture is complete 4 Architecture is described clearly 8 Chapter 7: Design: Architecture and Methodology 1 Design Topics Covered Architectural vs. detailed design “Common” architectural styles, tactics, and reference architectures Basic techniques for detailed design Basic issues with user-interface design 2 Design Starts mostly from/with requirements (evolving mostly from functionalities and other non-functional characteristics). How is the software solution going to be structured? What are the main components—(functional comp)? Often directly from requirements’ functionalities (use cases).
- 3. How are these components related? Possibly re-organize the components (composition/decomposition). Two main levels of design: Architectural (high level) Detailed design How should we depict design—notation/language? 3 Relationship between Architecture and Design Detailed Design Comes from Requirements & Architecture 4 Software Architecture Structure(s) of the solution, comprising: Major software elements Their externally visible properties Relationships among elements Every software system has an architecture. May have multiple structures! Multiple ways of organizing elements, depending on the perspective
- 4. External properties of components (and modules) Component (module) interfaces Component (module) interactions, rather than internals of components and modules 5 Views and Viewpoints View – representation of a system structure 4+1 views (by Krutchen) Logical (OO decomposition – key abstractions) Process (run-time, concurrency/distribution of functions) Subsystem decomposition Physical architecture +1: use cases Other classification (Bass, Clements, Kazman) Module Run-time Allocation (mapping to development environment) Different views for different people 6 Architectural Styles/Patterns Pipes and filters
- 5. Event driven Client-server Model-view-controller (MVC) Layered Database centric Three tier We discuss architectural styles/patterns as “reusable” starting point for design activities. 7 Pipe-Filter Architecture Style The high-level design solution is decomposed into two “generic” parts (filters and pipes): Filter is a service that transforms a stream of input data into a stream of output data. Pipe is a mechanism or conduit through which the data flows from one filter to another. Input time cards Prepare for check processing Process checks Problems that require batch file processing seem to fit this architecture: e.g., payroll, compilers, month-end accounting. ** Reminds one of DFD without the data store or source sink.** 8
- 6. Event Driven (Real Time) The high-level design solution is based on an event dispatcher, which manages events and the functionalities that depend on those events. These have the following characteristics: Events may be a simple notification or may include associated data. Events may be prioritized or be based on constraints such as time. Events may require synchronous or asynchronous processing. Events may be “registered” or “unregistered” by components. Personal (device) dispatcher voice call text msg Image keypad Phone processing Text processing Image processing
- 7. Problems that fit this architecture include real-time systems such as: airplane control, medical equipment monitor, home monitor, embedded device controller, game, etc. - - - Try a commercial flight control system - - - 9 Basic Client-Server Style Application split into client component and server component. 10 Client-Server Style Client may connect to more than one server (servers are usually independent). 11 Separates model (data) from view. Controller often integrated with view nowadays. Model-View-Control (MVC) Style Most internet web applications fall under this style.
- 8. 12 The “outer” layer can only ask for service from the “inner” layer; the “upper” layer can only ask for service from the “lower” layer. − Strict layering: only directly inside or below layers − Relaxed layering: any inside or below layers Layered Style 13 Shared Data (DB)-Centric Style Very popular within the business applications community 14 Three-Tier Style (Mixture) Clients do not access DB directly. Better flexibility, integrity. (Why?) Reminds one of client server or MVC. 15 Architectural Tactics Tactics (in contrast to architectural style) are for solving
- 9. “smaller, specific” problems. Do not affect overall structure of system. Example: we add specific functionalities or component (e.g., to increase reliability) in the design for fault detection—especially for distributed systems: Heartbeat Ping/echo 16 Reference Architectures Full-fledged architectures. Serve as “templates” or as “a reference” for a class of systems. Example: J2EE reference architecture (MVC2). There also are “application domain−specific” reference architectures. 17 Detailed Design Further refine architecture and match with requirements. How detailed? How formal? Maybe of different levels of detail for different views.
- 10. 18 Functional Decomposition Technique Dates back to “structured programming” [now (non-OO) Web apps with PHP tool]. Start with: main (task/requirements) --> module. Refine into sub-modules. There are alternative decompositions. 19 Possible Decomposition of (Student-Course Management App) 20 “Alternative” Decomposition/Composition 21 Relational Database Design Most databases use relational technology. Relations (tables):
- 11. Two-dimensional sets Rows (tuples), columns (attributes) A row may be an entity; columns may be relationships or attributes. Primary key (unique identifier) – for search Foreign keys (connects tables) 22 Database Design Conceptual modeling (done during analysis/requirement phase) produces ER diagram. Logical design (to relational). Physical design (decide data types, etc.). Deployment/maintenance: Low-level physical (which hard drive, etc.) Adjustment of indexes 23 Entity-Relationship Diagrams Entities (rectangles) Weak: double lines Relationships (diamonds) Attributes (ovals) Multi-valued: double lines Identifying: underlined
- 12. 24 ER Diagram Example 25 Logical DB Design – Entities Table per entity. Flatten composite attributes. For weak entities, add the primary key of the strong entity. 26 Logical DB Design – Multi-Valued New table needed for multi-valued attributes. 27 Logical DB Design – Relationships If one side related to just one entity, add foreign key to that side. For many to many, need new table. For ternary, need new table.
- 13. 28 Physical DB Design Data types for each attribute. Check which ones your DBMS support. Encoding. Decide on indexes. Searches are faster, updates are slower. Indexes consume space. Can always adjust during deployment. Denormalization done sometimes (avoid). 29 OO Design First step: review and refine use cases. Decide: Which classes to create How are the classes related Use UML as the design language. 30 Use Case Diagram
- 14. 31 Class Design Classes represent real-world entities or system concepts. Organized into classes: objects in a class have similar characteristics. Classes have properties (attributes or data). Classes also have methods (perform functions). 32 UML Class Diagrams Association Composition Use “no-fill” diamond for aggregation. 33
- 15. UML Class Diagrams – Inheritance 34 UML State Diagram depicting a student’s “status” in school 35 UML “Sequence Diagram” used to depict a flow of interactions 36 User Interface Design Most apparent to the user Two main issues: Flow of interactions ii) Look and feel Types of interfaces Command-line Text menus Graphical (GUI)
- 16. 37 Flow of Interactions Prototype screens Registration: Select term. Registration: shows term. Select first course. Registration: shows term, course(s) with schedule and cost. Select *Additional course; *Delete course; *Finish registration. Registration: shows final schedule. Select Confirm or Cancel. 38 High Fidelity Prototype 39 User: Screens: Process: User Interaction Added to the Sequence Diagram
- 17. 41 Norman’s 7 Stage Model 42 The GOMS Model (an “advanced” topic for UI) Consider different kinds of users. Four factors (for the kind of user) Goals of the user Operations provided by the system Methods or the sequence of operations Selection rules for the methods 43 Other UI Issues Kinds of users Heuristics UI guidelines Multicultural issues Metaphors Multiplatform software Accessibility Multimedia interfaces
- 18. 44 HTML Script Simple Example 45 Model-View-Controller (MVC) Software Project Model SQL database View HTML Controller PHP 46 Object-Relational Impedance Mismatch (an “advanced” topic) How do we handle mismatches between object-oriented concepts and relational DB such as: Typing Private and public Inheritance and polymorphism Nested structure versus table structure 47