In this paper, a multimedia synchronization model is proposed. The purpose of this model is description for temporal relationships(i.e. time ordering and synchronization for multimedia presentation) among various media. In the model, user interactions, such as conditional branching and menu selection, are also considered. For the description of the temporal relationships, Boolean Expressions are used. The concept of media objects would be a great help to manipulate multimedia data. The functions of the media objects are defined in this paper. A media object is an entity that contains associated data and a media variable representing its presentation state. Various types of media are classified into two types: OUTPUT and INPUT media objects. OUTPUT media objects have data perceived by the user such as graphics, image, drawings, animation, audio and video. INPUT media objects such as buttons and menus can handle input from the user. Temporal relationships among media objects can be represented by a set of presentation expressions consisting of a boolean expression; three logical operators(and, or, and not) and media variables. The value of the media variable indicates the state of media(e.g., in the case of video object, it has two states; playing and not playing.) Furthermore, by describing temporal relationships between input media objects and output media objects, user interaction can be successfully described in our model. A multimedia animal guide system, prototype system base on the model, was implemented. The system can synchronously present the media such as video, audio, image, and text, and can explain the feature and characteristics of animals, and the sequence of the presentation can be controlled by the user.