第 13 章 文档、超文本和 MHEG 标准

1. 第13章 文档、超文本和MHEG标准 Chapter 13 Documents ,Hypertext and MHEG

2. 文档 (Documents) • 多媒体文档至少应包含一种连续（依赖于时间）媒体和一种离散（不依赖于时间）媒体的信息，不同媒体或信息单元通过同步关系集成在一起。 • A multimedia document is a document which is comprised of information coded in at least one continuous (time-dependent) medium and in one discrete (time-independent) medium.

3. 多媒体文档与它的生成工具、数据抽象、基本概念和文档体系结构环境紧密相关。多媒体文档与它的生成工具、数据抽象、基本概念和文档体系结构环境紧密相关。 • A multimedia document is closely related to its environment of tools, data abstractions, basic concepts and document architecture.

4. 文档结构(Document Architecture) • 交换文档需要交换文档的内容和文档结构。这要求两个文档有相同的文档结构。 • Exchanging documents entails exchanging the document content as well as the document structure. This requires that both documents have the same document architecture.

5. 目前已经标准化或正在形成标准的体系结构是标准通用置标语言（SGML）和开放（OAD）。 • The current standardized , respectively in the progress of standardization, architectures are the Standard Generalized Markup Language (SGML) and the Open Document Architecture (ODA).

6. 信息体系结构使用它们的数据抽象和有关概念。信息体系结构使用它们的数据抽象和有关概念。 Information architectures use their data abstractions and concepts. • 文档体系结构描述了以模型的形式表示的不同元素之间（如描述模型、处理模型）的联系。 A document architecture describes the connections among the individual elements represented as models (e.g., presentation model, manipulation model).

7. 文档体系结构中的元素和它们之间的关系如图13.1所示。文档体系结构中的元素和它们之间的关系如图13.1所示。 The elements in the document architecture and their relations are shown in Figure 13.1.

9. 图13.2给予出了包含单个离散媒体单元和连续媒体单元间关系的多媒体文档体系结构。图13.2给予出了包含单个离散媒体单元和连续媒体单元间关系的多媒体文档体系结构。 Figure 13.2 shows a multimedia document architecture including relations between individual discrete media units and continuous media units.

11. 超文本和超媒体 Hypertext and Hypermedia • 超文本、超媒体和多媒体 Hypertext, Hypermedia and Multimedia

12. 1.非线性信息链(Non-linear Information Chain) • 超文本和超媒体有一个主要特征，即非线性的信息连接。不仅存在固定的阅读顺序，读者也可以决定自己的阅读路径，超文本的结构是一个图，由节点和边组成。 • Hypertext and hypermedia have as a major property a non-linear information link. There exists not only a reading sequence, but also the reader decides on his/her reading path. A hypertext structure is a graph ,consisting of notes and edges.

13. 节点是一个真实的信息单元。例如，文本元素、单个图形、声音或视频LDU。信息单元大多显示在用户界面上它们自己的窗口中。节点是一个真实的信息单元。例如，文本元素、单个图形、声音或视频LDU。信息单元大多显示在用户界面上它们自己的窗口中。 • The notes are the actual information units. They are, for example, the text elements, individual graphics, audio or video LDU s. The information units are shown at the user interface mostly in their own windows.

14. 边提供对其他信息单元的链接。这些通常被称为指针或链接。指针大多是一条有向边并且也包含它自己的信息。边提供对其他信息单元的链接。这些通常被称为指针或链接。指针大多是一条有向边并且也包含它自己的信息。 • The edges provide links to other information units. They are usually called pointers or links. A pointer is mostly a directed edge and includes its own information too.

15. 2.锚(Anchor) • 在线性排序过的文档中前移表明对图进行浏览。在用户界面上，指针的原点必须被标出，这样用户可以移到更深的信息单元。指针这个原点称为锚。用户界面有一个主要因素是锚的概念：锚如何能被恰当地表现? • The forward movement in linear sorted documents is called a navigation through the graph. At the user interface, the origin of pointers must be marked, so that the user can move to a further information unit. This origin of a pointer is called an anchor. A main factor of the user interface is the user interface is the concept of the anchor: how can the anchor be represented properly?

16. 与媒体无关的表现可以通过对一般的图形元素（如按钮）的选择来完成。与媒体无关的表现可以通过对一般的图形元素（如按钮）的选择来完成。 A media-independent representation can happen through the selection of general graphical elements, such as buttons.

17. 在文本表示方法中，可以用不同词、段落或不同长度的文本段来表示，鼠标放置在标出的区域，双击这块区域会导致与击打住处相连的目标节点的显示（如图13.11）在文本表示方法中，可以用不同词、段落或不同长度的文本段来表示，鼠标放置在标出的区域，双击这块区域会导致与击打住处相连的目标节点的显示（如图13.11） In a text, individual words, paragraphs or text sections of different length can be used for representation. The positioning of the pointer to the marked area and double clicking in this area leads to a display of the destination node, connected with the clicked information (e.g. see Figure 13.11).

19. 对图像而言，特定的图形目标或是简单区域都可以定义成选择目标。可通过颜色或条纹作标志。对图像而言，特定的图形目标或是简单区域都可以定义成选择目标。可通过颜色或条纹作标志。 In images, specific graphical objects or simply areas are defined as selection objects. A specific marking can occur through a color or stripe. • 对运动视频而言，可使用与媒体无关的表现方法，也可以使用随时间改变的区域图示。 In a motion video, media-independent representations of the anchor are preferred. There can also be time-changing areas used.

20. 对于声音而言，也是使用与媒体无关的方法，在这种情况下宁可显示一段短的、描述性的文字或是图标大小的图像。对于声音而言，也是使用与媒体无关的方法，在这种情况下宁可显示一段短的、描述性的文字或是图标大小的图像。 • With respect to audio, a media-independent solution is used. In this case, a short ,descriptive text or an image of the size of an icon is preferably shown.

21. 3.超文本系统(Hypertext System) • 超文本系统主要通过信息的非线性链接决定。不同节点的数据可以一种或几种媒体类型表现，在纯文本系统中只有文本部分被链起来，我们把超文本理解为包含多种媒体链接的信息实体。 A hypertext system is mainly determined through non-linear links of information. Pointers connect the nodes. The data of different nodes can be represented with one or several media types. In a pure text parts are connected. We understand hypertext as an information object which includes links to several media.

22. 4.多媒体系统(Multimedia System) • 多媒体系统包含至少有连接的和离散的介质表现的信息。 • A multimedia system contains information which is coded at least in a continuous and discrete medium.

23. 5.超媒体系统(Hypermedia System) • 超媒体系统包含了超文本系统的非线性信息和多媒体系统的连续和离散媒体。例如，如果一个非线性连接包含文本和视频数据，那么它就是一个超媒体、多媒体和超文本系统。 • A hypermedia system includes the non-linear information links of hypertext systems and the continuous and discrete media of multimedia systems. For example, if a non-linear link consists of text and video data, then this is a hypermedia, multimedia and hypertext system.

24. 系统：结构、节点和指针 (System: Architecture, Nodes and Pointers) 1.结构(Architecture) • 超文本系统的结构可以被分成带有不同功能的三层[CG87]： The architecture of a hypertext system can be divided into three layers with different functionalities [GG87]:

25. 表现层：在最上面的表现层包含了所有与用户界面有联系的功能。这里，节点和指针被映射到用户界面。表现层：在最上面的表现层包含了所有与用户界面有联系的功能。这里，节点和指针被映射到用户界面。 Presentation Layer: At the upper layer, the presentation layer, all functions connected to the user interface are embedded. Here nodes and pointers are mapped to the user interface.

26. 超大型文本抽象机（HAM）：超文工抽象机处于表现层和存储层之间，它只考虑下层所提供的在分布式环境中存储多媒体数据库功能，而不需要考虑上一层的输入和输出。超大型文本抽象机（HAM）：超文工抽象机处于表现层和存储层之间，它只考虑下层所提供的在分布式环境中存储多媒体数据库功能，而不需要考虑上一层的输入和输出。 • Hypertext Abstract Machine: The Hypertext Machine (HAM) is placed between the presentation and storage layers. It can expect from the underlying layer database functions for storage of multimedia data in a distributed environment. It does not have to consider input and output of the upper layer.

27. 存储层：存储层（也称数据库层）是最低一层，与数据存储联系的所有功能（即辅存管理）都属于这一层，需要考虑不同抽象和连续媒体的特殊性性。存储层：存储层（也称数据库层）是最低一层，与数据存储联系的所有功能（即辅存管理）都属于这一层，需要考虑不同抽象和连续媒体的特殊性性。 • Storage Layer: The storage layer (also called the database layer) is the lowest layer. All functions connected with the storage of data (secondary storage management) belong to this layer. The specific properties of the different discrete and continuous media need to be considered.

28. 2.节点节点是超文本文档中的住处单元（LDU） A node is an information unit (LDU) in a hypertext. 3.指针(Pointers) • 指针是超文本图的边，超文本系统根据边的作用的不同使用不同的标准进行分类。 Pointers are the edges of a hypertext graph. Hypertext systems are classified according to different criteria with respect to edges.

29. 4.工具(Tool) • 超文本系统由几个必需的工具组成。编辑器处理以不同的媒体表现的信息，除此之外还要支持指针的产生、管理、编辑和删除。 • A hypertext system consists of several necessary tools. Editor process information represented in different media. Beside this, the generation, management, editing and deletion of pointers are supported.

30. 捜索工具允许捜索需要的住处当然也必须考虑不同的媒体。捜索工具允许捜索需要的住处当然也必须考虑不同的媒体。 Search tools allow the search of desired information. Also, different media need to be considered. • 浏览器允许简单且清楚地表现节点和边，节点以依赖于媒体的方式描述。 Browser allows a shortened but clear representation of the nodes and edges. The nodes are described media-dependently.

31. 多媒体和超媒体住处编码标准MHEG • 音频、图像、超媒体编码委员会（ISO/IEC/JTC1/SC29）负责多媒体系统的交换格式的标准化工作。实际的国际准由三个工作组负责制定。在制定过程中，工作组与研究机构以及工业界进行了广泛的合作。 • The committee Coding of Audio, Picture, Multimedia and Hypermedia Information (ISO/IEC JTC1/SC29) works on the standardization of the exchange format for multimedia systems. The actual standards are developed at the international level in three working groups cooperating with research and industry.

32. 图13.24表示处理单个媒体的编码和压缩的三个标准.图13.24表示处理单个媒体的编码和压缩的三个标准. • Figure 13.24 shows that the three standards deal with the coding and compression of individual media.

34. 工作组的成果有：JPEG（联合图像专家组）和MPEG（活动图像专家组），这两个标准目前已广泛用于多媒体系统领域中（见第6章所述的压缩标准）。工作组的成果有：JPEG（联合图像专家组）和MPEG（活动图像专家组），这两个标准目前已广泛用于多媒体系统领域中（见第6章所述的压缩标准）。 • The results of the working groups: JPEG (the Joint Photographic Expert Group) and MPEG (the Motion Picture Expert Group) are of special importance in the area of multimedia systems (see Chapter 6 on compression.)

35. 交互多媒体表现的示例 Example of an Interactive Multimedia Presentation • 在给出MHEG对象的细节描述之前，我们将用一个小场景简要说明一个表现的各个元素。图13.25给出一个交互多媒体表现的时间图。 Before a detailed description of the MHEG objects is given, we will briefly examine the individual elements of a presentation using a small scenario. Figure 13.25 presents a time diagram of an interactive multimedia presentation.

37. 表现由某段音乐开始，当音频序列中一出现播音员的声音，一幅图将在屏幕上出现数抄。表现由某段音乐开始，当音频序列中一出现播音员的声音，一幅图将在屏幕上出现数抄。 • The presentation starts with some music. As soon as the voice of a news-speaker is heard in the audio sequence, a graphic should appear on the screen for a couple of seconds.

38. 在图像消失后，观众详细读到一段文字。文字显示结束后，一个“停止”按钮出现在屏幕上。用户可以用该按钮终止音频序列。在图像消失后，观众详细读到一段文字。文字显示结束后，一个“停止”按钮出现在屏幕上。用户可以用该按钮终止音频序列。 • After the graphic disappears, the viewer carefully reads a text. After the text presentation ends, a Stop button appears on the screen. With this button the user can abort the audio sequence.

39. 现在，用户用一个显示出来的框输入提示所需的视频序列的标题。这些视频数据在输入框的个性完成后立即显示出来。现在，用户用一个显示出来的框输入提示所需的视频序列的标题。这些视频数据在输入框的个性完成后立即显示出来。 • Now, using a displayed input field, the user enters the title of a desired video sequence. These video data are displayed immediately after the modification.

40. 1.内容(Content) • 表现由一个信息的序列构成。为表示该信息，要使用不同性性的媒体。为了便于以后的重用，应把每个信息LDU作为单独对象录。本例中，表现的内容包括视频序列音频序列、图像和文本。 • A presentation consists of a sequence of information representations For the representation of this information, media with very different properties are available. Because of later reuse, it is useful to capture each information LDU as an individual object. The contents in our example are: the video sequence, the audio sequence, the graphics and the text.

41. 2.行为(Behavior) • 行为包含了表示内容的所有信息并定义表现过程。前者由“开始”、“设置音量”和“设置位置”等动作控制。后者由单独元素间的时序、空间和条件链的定义决定。 • The notion behavior means all information which specifies the representation of the contents as well as defines the run of the presentation. The first part is controlled by the actions start, set volume, set position, etc. The last part is generated by the definition of timely, spatial and conditional links between individual elements.

42. 如果内容表现的状态变了，这可能导致把某些命令作用其他对象上（例如，图像的删除导致文本的显示）。还有一种可能性，表现的行为可以在外部的程序或函数（脚本）被调用时决定。如果内容表现的状态变了，这可能导致把某些命令作用其他对象上（例如，图像的删除导致文本的显示）。还有一种可能性，表现的行为可以在外部的程序或函数（脚本）被调用时决定。 • If the state of the content is presentation changes, then this may result in further commands on other objects (e.g., the deletion of the graphic causes the display of the text). Another possibility, how the behavior of a presentation can be determined, is when external programs or functions (script) are called.

43. 3.用户交互(User Interaction) • 在上述场景中，动画可由相应的用户交互动作来终止。可以有两用户交互。第一种是“简单选择”，它通过一个特定的选择控制表现的流程（例如，按“停止”按钮）。 • In the discussed scenario, the running animation could be aborted by a corresponding user interaction. There can be two kinds of user interactions. The first one is the simple selection, which controls the run of the presentation through a prespectified choice (e.g., push the stop button).

44. 第二种是较复杂的“修改”，用户可以在表现的过程中输入数据（例如，编辑一个数据输入框）。第二种是较复杂的“修改”，用户可以在表现的过程中输入数据（例如，编辑一个数据输入框）。 • The second kind is the more complex modification, which gives the user the possibility to enter data during the run of the presentation (e.g., editing of a data input field)

45. 4.包容体(Container) • 通过把几种媒体按上述方式合并在一起，就得到了一个随时间进行的表现。为能在所涉及的系统中交换该表现，必须用一个复合元素。该元素类似一个包容体。它把所有元素链接成一个单元。 • Merging together several elements as discussed above, a presentation, which progresses in time ,can be achieved .To be able to exchange this presentation between the involved systems, a composite element is necessary. This element is comparable to a container. It links together all the objects into a unit .

46. 对于超文本/超媒体文档而言，使用超文本措针，这样的包容体可以排列成一个复杂结构。对于超文本/超媒体文档而言，使用超文本措针，这样的包容体可以排列成一个复杂结构。 • With respect to hypertext/hypermedia documents, such containers can be ordered to complex structure, if they are linked together through so- called hypertext pointers.

47. 内容(Contents) 1.内容类 • 内容类和其他不同，因为它提供了到实际内容的链按。通过这个内容类，信息变得更灵活，并在系统中以一种开放的方式链接起来。在一个表现中，每个内容对象都表达一个确切的信息。 • The content class differs from the other chasses because it provides the link to the actual contents. Through this content class, this information becomes flexible and is linked together in an open way in the system. Each content object represents exactly one information within a presentation.

48. 2.虚拟坐标系 • 在虚拟坐标空间中，内容对象可相对于坐标进行定义和排序。有三个轴：X（宽），Y（高）和Z（深）。坐标值范围为一32768到32767。 • The so-called Generic Space defines a virtual coordination system. Content objects can be defined relative in dimension and ordering to each other. There are three axes: X (width), Y (height) and Z (depth). A value from -32768 to 32767 is assigned to each axis.

49. 在运行时，虚拟MHEG坐标要在特定期表现服务（例如，覆盖Motif窗口的像素数）中变换成物理坐标。另外还有一个带有坐标轴T的时间坐标系。该轴的值域是0到无穷的一个间隔，单位是一个微秒。在运行时，虚拟MHEG坐标要在特定期表现服务（例如，覆盖Motif窗口的像素数）中变换成物理坐标。另外还有一个带有坐标轴T的时间坐标系。该轴的值域是0到无穷的一个间隔，单位是一个微秒。 • During the run-time, a translation from the virtual MHEG coordinates to the physical coordinate system is performed in the particular presentation service (e.g., the number of pixels which cover a Motif window). Additionally ,a time coordinate system exists with its axis T. The defined value set for this axis is an interval from 0 to infinity where the scale unit is a millisecond.

50. 3.虚拟视图(Virtual Views) • 到目前为止，我们假设内容的表现和原始产生出来的相同，实际上MHEG提供一套通过适当参数控制内容表现的方法。 • Until now we assumed that the presentation of the contents occurs exactly as originated, Actually, MHEG provides a set of possibilities which can control a presentation of the content objects through proper parameters.