The third part of object-oriented design
3.1 Object-Oriented Design (OOD) of the definition?
In object-oriented analysis phase, system analysis model with object-oriented concepts described has been established for the user's needs. At the design stage, to consider computer equipment for the realization of the system and the use of relevant factors operating systems, network, database management systems and programming languages used to further the use of object-oriented approach to system design, finally forming an achievable design model, that is, object-oriented design model.
3.2 Object-Oriented Design (OOD) object analysis (OOA) oriented relationship with?
In object-oriented analysis phase, for the real world, the conversion of demand for the model object-oriented concepts created for ease of understanding of the problem domain and system responsibility, the eventual establishment of a problem domain mapping to meet the needs of users, independent of the OOA model implementation , object-oriented design is the use of object-oriented method based on object-oriented analysis and implementation of the major issues to resolve related ,, OOD goal is to generate a model to achieve compliance with specific conditions. Because based OOA to OOD, OOA and OOD consistent with the representation, so that there is transition from OOA to OOD, only necessary corrections and adjustments. The gap between the traditional methods in the analysis and design exists between OOA and OOD, both can be closely co-ordinated. Stage does not emphasize the division between OOA and OOD, OOA and OOD but has a different focus and a different division of labor, and therefore have different development processes and specific strategies. "Analysis" for only the problem domain and system responsibility, do not consider implementing relevant factors, to establish an independent in OOA model implementation; design is to consider the issue and implementation of related, such as the selection of programming languages, database systems and graphical user interfaces, OOD model for the establishment of a specific implementation.
3.3 Object-Oriented Design (OOD) features?
- In object-oriented analysis is based, it is generally not dependent on the structure analysis
- OOA and corresponding methods constitute OOA & D methodology, OOA and OOD consistent concepts and principles, but belong to different phases of the software life cycle, have different goals and strategies
- More fully embodies the concepts and principles of object-oriented approach
- Most OOD method is independent of programming language, but OOD specific application, will have to consider the particular programming language, it is because the system model is obtained by the object-oriented design, is determined to be implemented by a programming language
3.4 Object-Oriented Design (OOD) process and the process model?
In OOA stage only consider the problem domain and system responsibilities, will have to consider implementation-related issues in OOD stage, the aim is to
- The general framework of the problem domain and organizational nature of the long-term stability, and variable details
- The stabilizing portion (part of the problem domain) and the variable portion (the portion related to implement) apart, so that the system can comfortably accommodate changes
- In favor of the same model for different design and realization
- Analysis and Design of family support systems and similar systems
- Make a success of the system has exceeded its lifetime scalability
To achieve the above object, object-oriented design follows the design model
OOD model from a side view, comprising a central portion, i.e., part of the problem domain; further comprises four peripheral portions, i.e., human-computer interaction, the drive control section, and the data management section member and deployment section. The initial part of the problem is the domain model OOA, to be adjusted in accordance with the supplementary conditions achieved; interactive human-machine interface that is part of the design portion; i.e., controls the driving section to define and control various coordinated concurrent flow; data management section modeling for accessing persistent objects; model deployment member and the member section describes the relationship between the member and the member, the deployment model is used to describe the nodes, the nodes and the relationship between the junction member Distribution.
OOD process
- Part of the problem domain design
- Human-computer interaction design
- Design of the drive control section
- Data management part of the design
3.4.1 Design of the domain part of the problem
Part of the problem domain is made and problems related to the object, and part of the user to provide the desired function on the specific implementation platform. It is make the necessary changes, adjustments and details as required to achieve the OOA model on the basis of supplementary obtained.
The problem domain is part of the design process:
- Enter OOA model and make the necessary changes
- Condition implemented individually investigate the influence of the field part of the design, the model is adjusted accordingly and supplement
- Mapping relationship between the analysis of documents and design documents
Design and content strategy
(1) adjusted for programming language support capabilities: including inheritance and polymorphism adjustment adjustment
(2) increasing the general class, there is provided a common protocol
(3) In order to achieve design reuse strategy adopted: Direct reuse; remove the extra information like reusable; remove the extra information, through inheritance and the multiplex; reuse through inheritance
(4) to improve performance: the data transmission time, data access time and data processing time is three viewpoints
(5) In order to achieve the object changes made persistent storage
(6) details of the perfect object: to make up for lack of OOA model; problem solving OOA node postpone consideration; operational design objects; design representations associated attributes (one to one, one to many); Design represents a whole - part relationship Attributes
(7) define an object instance
(8) to modify or supplement aid models and the Statute
3.4.2 human-computer interaction design
How to human-computer interaction prominent people command system and how the system to submit information to the user. Interactive design is to design the input and output objects contained therein (called interface object) and the relation therebetween constitutes a model of human-computer interaction systems.
OO design man-machine interface: General is of the elected interface support system based on the use of its support structure interface components, a design can meet the needs of human-computer interaction, human-computer interface design features of the model fit the user.
- Interface support system include: Window System, a graphical user interface, visual programming environment
- Interface elements: windows, menus, dialog boxes, scroll bars, Other
The design process and strategy:
Object-oriented man-machine interface design is based on man-machine interaction needs analysis to the selected interface support system as the background, select required to achieve human-computer interaction interface elements to construct man-machine interface, and object-oriented concepts and representation to represent the relationship of these elements and an interface therebetween, thereby forming the human-computer interaction model of the entire system OOD
- Select and control interface support system: consider the hardware, operating system and programming language; support level interface implementation; interface style and visual sense; the other (software price, which operating system familiar)
- According to human-machine interaction needs to choose interface elements: system startup; to achieve high-level organizational structure of the command; execute basic commands; abnormal input command; input and output detailed interaction process
- OO concepts represented by interface elements: classes and objects; attributes and operations; Overall - partial structure; Fair - special structure; association; message
- Design principles: minimize user input; validity check (such as the format of check for);
Human-computer interaction design guidelines
- Easy to learn, easy to use, easy to operate
- Try to keep consistency
- Timely provide meaningful feedback
- Try to reduce the user's memory
- Reduce duplication operation input and
- Providing a context-sensitive functions
- Prevent catastrophic error
ps: command
Basic commands: using an independent command system function
Step order: an input step of performing a specific basic commands contained in the interaction
Senior command: a command is done under the guidance of another command
3.4.3 Design of the driving control portion
Driven by the system control section composed of all active class, which describes a system for active class of all the active objects, each active object is a drive control system stream. A flow control is a process (both resource allocation unit processor unit is allocated to other resources) or thread (just the processor resource allocation unit)
The design process and strategy:
- Select Software Architecture Style: All things considered, to make a reasonable trade-off
- Distribution scheme determination system: the data distribution function and the distribution of considerations, including distributed objects, distribution class, and in the distribution class diagram showing classes of the statute
- Control flow identification: identifying units of the node to the control flow; the user needs to know the flow of control use cases; parallel computing, controlling the flow of communication between the node; coordinating control other control flow stream
- A control flow by the active object
- The control of the drive as a package
3.4.4 Data Management part of the design
Data management component is responsible for the application of objects in the selected data storage management system, and stores the result back to the application system, for data storage, retrieval, management and maintenance of the system is called a data management system, including file systems and database systems into two categories.
Due to the current object-oriented database it is not widely used, so we were still based relational database, storage and retrieval of data.
Database (DB): long-term database is stored in the computer, organized, sharable data collection
Database management system (DBMS): DBMS is used to create, use and maintenance of database software. It unified database management and control, in order to ensure the security and integrity of the database
Relational databases and object-oriented approach does not match, because: a relational database is not fully support all of the concepts in object-oriented, such as the relations between classes (inheritance, polymorphism)
Non-relational databases: the advantage of storing any object, disadvantage is non-relational database structures difficult operation
Object-oriented database: using object-oriented data model database called the basic concepts of object-oriented database, object-oriented support
The basic database design process:
- Conceptual design phase: the user information requirements into a unified whole logical structure, this structure can express the user's requirements, and independent of any DBMS software and hardware
- Logical design phase: the results obtained in the conceptual design phase transformation logic and data model structure supported by the DBMS chosen to conform
- Physical design: given a logical data model to select the most suitable physical structure requirements of the application. The physical structure of the database comprises a database stored in a recording format, recording schedule storage access method, which is entirely dependent on the given hardware environment and database products
3.4.5 deployment member and part of the design
Members, respectively, and Deployment for system design and deployment member design.
FIG member design: using a member of the physical implementation of object-oriented modeling system, modeling elements is one of the main products, the products can be divided into work product article (product development process, such as source code and data files, etc.) may be deployed products (such as dynamic link library dll or exe executable file). Member of the specific physical modeling, until the deployment member can be produced.
FIG deployment design : a network topological structure of the system, it can also be used to show the deployment member at the nodes. Mainly used for embedded systems and distributed systems modeling
Specific reference member design and Deployment
Reference books
"Object-Oriented Jitongfenxi" (2nd edition) Shao Weizhong Yang Fuqing the
"UML object-oriented technology tutorial" edited by Wang Shaofeng