外文翻譯----高級數(shù)據(jù)庫應(yīng)用(文件)
【正文】 and progress monitoring. Network management systems Network management systems coordinate the delivery of munication services across a 信息與計算科學(xué)畢業(yè)設(shè)計 3 puter work. These systems perform such tasks as work path management, problem management, and work planning. As with the chemical manufacturing example we discussed earlier, these systems also handle plex data and require realtime performance and continuous operation. For examples, a telephone call might involve a chain of work switching devices that route a message from sender to receiver, such as: Node? Link? Node? Link? Node? Link? Node Where each Node represents a port on a work device and each Link represents a slice of bandwidth reserved for that connection. However, a node may participate in several different connections and any database that is created has to manage a plex graph of relationships. To route connections, diagnose problems, and balance loadings, the work management systems have to be capable of moving through this plex graph in real time. Office information systems (OIS) and multimedia systems An OIS database stores data relating to the puter control of information in a business, including electronic mail, documents, invoices, and so on. To provide better support for this area, we need to handle a wider range of data types other than names, addresses, dates, and money. Modern systems now handle freeform text, photographs, diagrams, and audio and video sequences. For example, a multimedia document may handle text, photographs, spreadsheets, and voice mentary. The documents may have a specific structure imposed on them, perhaps described using a markup language such as SGML (Standardized Generalized Markup Language), HTML (HyperText Markup Language), or XML (eXtended Markup Language), as we discuss in Chapter 29. Documents may be shared among many users using systems such as electronic mail and bulletinboards based on Inter technology. Again ,such applications need to store data that has a much richer structure than tuples consisting of numbers and text strings. There is also an increasing need to capture handwritten notes using electronic devices. Although many notes can be transcribed into ASCⅡ text using handwriting analysis techniques, most such data cannot. In addition to words, handwritten data can include sketches, diagrams and so on. In the DreamHome case study, we may find the following requirements for handling multimedia. ■ Image data A client may query an image data base of properties for rent. Some queries may simply use a textual description to identify images of desirable properties. In other cases it may 4 be useful for the client to query using graphical images of features that may be found in desirable properties (such as bay windows, internal cornicing, or roof gardens). ■ Video data A client may query a video database of properties for rent. Some queries may simply use a textual description to identify the video images of desirable properties. In other cases it may be useful for the client to query using video features of the desired properties (such as views of the sea or surrounding hills). ■ Audio data A client may query an audio database that describes the features of properties for rent. Some queries may simply use a textual description to identify the desired property. In other cases it may be useful for the client to use audio features of the desired properties (such as the noise level
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