vì vậy childNodes thực sự là một danh sách các nút có chứa tất cả các trẻ em của phần tử, để nguồn. Một khi chúng ta có một tham chiếu đến các yếu tố neo, chúng ta có thể nhận được một tham chiếu đến đoạn cha mẹ của nó | 14 2 An object-oriented design process 327 locations such as offices organisational units such as companies and so on Shlaer and Mellor 1988 Coad and Yourdon 1990 Wirfs-Brock et al. 1990 . Support this by identifying storage structures abstract data structures in the solution domain that might be required to support these objects. 3. Use a behavioural approach where the designer first understands the overall behaviour of the system. The various behaviours are assigned to different parts of the system and an understanding is derived of who initiates and participates in these behaviours. Participants who play significant roles are recognised as objects Rubin and Goldberg 1992 . 4. Use a scenario-based analysis where various scenarios of system use are identified and analysed in tum. As each scenario is analysed the team responsible for the analysis must identify the required objects attributes and operations. A method of analysis called CRC cards where analysts and designers take on the role of objects is effective in supporting this scenario-based approach Beck and Cunningham 1989 . These approaches help you get started with object identification. In practice you may have to use several knowledge sources to discover object classes. Object classes attributes and operations that are initially identified from the informal system description can be a starting point for the design. Further information from application domain knowledge or scenario analysis may then be used to refine and extend the initial objects. This information may be collected from requirements documents from disc ussions with users and from an analysis of existing systems. I have used a hybrid approach here to identify the weather station objects. I don t have space to describe all the objects but I have shown five object classes in Figure . Ground thermometer Anemometer and Barometer represent application domain objects and Weatherstation and WeatherData have been identified from the system .
