Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville1 CSC-3324: Chapter 6 Software Design Section 10.3 (except )

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville2 The Typical Waterfall model embeds the following steps: Feasibility study Conceptual Analysis Design Implementation Maintenance. The Design Phase...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville3 Adapting the conceptual solution identified during the analysis step to the technology enablers (Platforms, Programming languages, DBMS, OS, Devices, etc.) that can/will be used for the project… Client constraints, Organizational constraints, the requirements, the software engineer profile, etc; The Design Phase...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville4 During the Design, we must perform the following tasks and produce their corresponding deliverables: Choose appropriate technology enablers... Set the functional architecture… Set the system architecture… Set the functions interactions (call, messages, events, etc.)… Building the DFDs… Building a logical data model... Set the functions interface… Write the algorithms... Design the user interfaces... The task to be performed...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville5 Choose appropriate technology enablers.. Programming language, Web tools, DBMS, Network protocol, Operating system, User Interface development tool, Platforms Etc.

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville6 Set the functional architecture… A Functional architecture contains, in a tree like hierarchy, all modules (nodes) and functions (leafs) of your system with the exact names as they will appear in the code… Directly derived from the conceptual architecture… Given the tools that have been selected for the development, we must adjust the leafs of the conceptual architecture... This can lead to changing leafs names, adding/dropping some hierarchical levels...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville7 Set the system architecture… (web oriented architecture…)

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville8 Set the system architecture… (web oriented architecture…) The client presentation layer: In web applications the user most often accesses this tier through a web browser, but other entry points are possible, such as desktop applications or entirely different devices using e.g. web services. The Server-Side Presentation Layer: contains the logic that allows the user to navigate the application. In this layer the presentation of the content to the user is determined. This Server-Side Business Logic layer: contains the business logic of the application. The functionality is divided into modular components, called EJBs (Enterprise Java Beans), and each bean is responsible for a defined area of the business logic, e.g. price calculation or customer data. Enterprise Information System layer: is the database server, containing the raw data

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville9 Protocols of Web architecture ODBC/ JDBC Web tier JSPs under Apache/Tomcat Windows/Linux Application server (Business tier) Business Rules/Logic J2EE platform Windows/Linux Primary Server Oracle/MySQL Replication Server Oracle/SQL Server Replication Data tier Main Data tier RPC/ RMI PC Internet Windows Touch Screen Windows PDAs JAVA VM HTTPSHTTPS Via GSM /GPRS or an access Point (using IEEE ) BROWSERSBROWSERS

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville10 Set the functions interactions How the different functions of the architecture are linked to each other… Interactions/dynamic model… Focus on: Time… When is it called? Sequence… Who calls? To whom the output is destined? Inputs/Outputs; Entrance/exit Conditions...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville11 Set the functions interactions Control models… Sequential (Centralized as called by Somerville) control: The call/return model; The manager Model; Event driven programming… Messages based (OO) interaction…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville12 Set the functions interactions… DFDs Data Flow Diagrams (DFDs) are a good way to graphically represent the functions interactions... A DFD shows the processing steps as data flows through a system... We may need separated DFDs and different levels of abstractions to model all processes… Based on the CPMs and the functional architecture…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville13 Set the functions interaction… DFDs A good DFD, must specify for each function: The Input data, The Input data, The entrance conditions (if ever), The entrance conditions (if ever), The output data, The output data, The exit conditions (if ever). The exit conditions (if ever).

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville14 Set the functions Interaction… DFDs

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville15 Set Functions Interface... Parameters (type, number, source); Local/Global Variables; Central/shared Database; Data structure…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville16 Building your logical data Model... Database (Relational: E/R- Objects: UML…) Files... Arrays... Record… Files/Queues...

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville17 Writing algorithms... What is an algorithm? What is the link with programming languages? What is the link with software engineering? Basic algorithmic constructs… How to write a good algorithms? Strategies…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville18 Writing algorithms... Basic algorithmic constructs… Alternatives: If Condition Then Sequence1 Else Sequence2… Case Condition Switch Sequence Break… Iterations: For IntervalValues Do Sequence… Repeat Sequence Until Condition… While Condition Do… Sequences: Begin Inst1, Inst2, …, Inst n End.

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville19 Programming your system… Coding different modules of your system with respect to the Technology Enablers… Component oriented programming… Structured/Quality programming… Documented/traceable programming…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville20 Structured/Quality Programming… All variables used in the program must be: Assigned: must be given a value before being used; Initialized: must be given a value before being used in a loop; Precise: must be given sufficient physical space in accordance with their type; Documented: commented at declaration and at use Auto-descriptive: significant name…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville21 Structured/Quality Programming… All functions/Modules must be: Parametrable: all inputs must be given as parameters; Encapsulated: does not use global variables; Generic /Abstract : perform a precise task that is understandable outside the technical context. Documented… minimum 10% ratio Code/Comment

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville22 Structured/Quality Programming… General rules: Indention… Alignment… One instruction per line… Avoid spaghetti expressions… No transtyping/Casting… No more than 2 nested Ifs… Use appropriate Iterative/alternative structures…

Soft. Eng. I, Fall 2006Dr Driss Kettani, from I. Sommerville23 Design the user interfaces... See User Interface chapter slides...