UML Model Hierarchy

· Model Hierarchy

For different purposes, the model can take various forms and different abstract layers. The amount of information contained in the model must correspond to the following purposes:

The high-level model established in the early stage of the project is used to focus on stakeholder ideas and emphasize some important options. These models describe the requirements of the system and represent the starting point of the system design. Early models help project initiators study possible project selection schemes before focusing on system details. As design progresses, early models are replaced by more precise models. There is no need to detail the various options and rework situations in the early research process. Early models aim to help you get ideas. However, the final "Train of Thought Model" should be recorded before detailed design. Early models do not need to be accurate in the implementation phase, and do not need to involve a set of concepts related to system implementation. This model only uses a subset of the components defined by UML, which is much less than the components used by the model in later stages of design.

When an early model develops to a complete view model with a certain degree of accuracy-for example, a model that analyzes system requirements-it should be saved when the development process enters the next stage. Incremental development that constantly adds information to the model (in this case, the development reasoning process should also be saved and recorded) there is an important difference between it and general loose development that studies "Dead ends" until the right solution is obtained. In the latter case, people do not know how to proceed, and there is no need to record the entire development process unless the development process needs to be traced back in special circumstances.

The abstraction of the basic structure of the system indicates that the models established in the analysis and preliminary design phases are centered on key concepts and various final system mechanisms. These models match the final system in some way. However, the detailed information is lost in the model and must be explicitly supplemented during the design process. Abstract models are used to correct common high-level system problems before handling local details. Through a careful development process, these models can be developed into the final model, which ensures that the final model can correctly implement the design intent of the initial model. You must have the tracking capability to track the process from the basic model to the complete model. Otherwise, it cannot be ensured that the final system correctly contains the key features to be expressed by the basic model. The basic model emphasizes semantics and does not need to involve system implementation details. Sometimes it is true that the difference in the lower-layer implementation will obscure the logical semantics. The path from the basic model to the final implementation model must be clear and concise, regardless of whether the process is automatically implemented by the code generator or manually implemented by the designer.

The detailed specifications of the final system indicate that the system implementation model contains sufficient information to build the system, it should not only include the logical meanings and syntaxes, algorithms, data structures of the system, but also ensure that the system functions can be correctly completed, but also include the organizational decisions of system products, these products are essential for individuals to collaborate with each other and to use auxiliary tools. This model must include components that package model elements for easy understanding and automatic processing by computers. This is not a feature of the target application system, but a feature of the system construction process.

A well-selected example of a typical or possible system can improve people's observation capabilities and make the system description and actual results available. However, even if there are a lot of examples, there is no detailed definition of the effect. In the end, we hope that the model can be used to illustrate the general situation, which is also what the program code needs to do. However, examples of typical data structures, InterAction sequences, or object lifecycles are helpful for understanding complex systems. Be careful when using the example. Logically speaking, it is impossible to sum up the most common situations from a large number of special cases, however, most people always consider some carefully selected examples of a problem. The sample model only describes the model without a general description. Therefore, people may think there is a difference between the two models. The sample model generally only uses a subset of the components defined by UML. Both the descriptive model and the sample model are useful in modeling.

A full or partial system description model can completely describe an independent system without reference to external information. More often, models are organized by different and discontinuous descriptive units. Each unit can be stored and manipulated separately as part of the overall description. This model carries a part that must be associated with other models of the system. Because of their relevance and meaning, they can be combined with other parts to construct different systems. Obtaining reuse is an important goal of a good modeling method.

The model needs to develop and change over time. In-depth and refined models are derived from abstract models, and specific models are derived from logical models. For example, the model created in the initial stage is a high-level view of the entire system. As time went on, the model added some details and introduced some changes. As time goes on, the core focus of the model changes from a user-centric front-end logic view to an implementation-centric back-end physical view. With the development process and in-depth understanding of the system, we must repeatedly describe the model at various levels for a better understanding, it is impossible to understand a large system from a single perspective or linear process. There is no difference between "correct" and "wrong" for the model form.