Tower object

In a hyperdocument an object can function multi-dimentionally, and hence a complete description of an object within a hyperdocument usually consist of several levels.

"A tower object is an object with a tower value. A tower value is a mapping from a set of labels to a set of objects. Each label is a description level, corresponding to a separate level of the hyperdocument functionality. The domain for the function is fixed for each class of tower objects. If the levels are always given in a specific order, one may represent a tower as a tuple of objects." [P. De Bra, G.J. Houben and Y. Kornatzky., An Extensible Data Model for Hyperdocuments, 4th ACM Conference on Hypertext, Milan, Dec 1992.]

An example figuring of a tower for a text node as follow:

Source: De Bra, P., Houben, G.J., Kornatzky, Y., An Extensible Data Model for Hyperdocuments, 4th ACM Conference on Hypertext, Milan, Dec 1992.

All kinds of objects are modeled by towers. The number and nature of the levels of different kinds of towers is completely arbitrary. It is possible to have a tower with only one level. This tailor ability of the tower structure permits the integration of information from outside the hypermedia system.

Composite tower is a tower which packages together the multiple levels of description of a composite object. As a composite object is a collection of objects which would be themselves towers, a level of the composite tower is built from the corresponding levels of the elements of the composite.

City object

"A city object is an object with a city value. A city value is a mapping from a parameter space into a set of tower objects." [P. De Bra, G.J. Houben and Y. Kornatzky., An Extensible Data Model for Hyperdocuments, 4th ACM Conference on Hypertext, Milan, Dec 1992.]

Different elements of a city deal with a different use of an object. Hence, this makes the difference between the city concept and the tower concept. However, the information is styled differently for separate users in order to create separate user views.

The city constructor packages together the different views of a basic or composite object. The elements (in the range) of a city are called views. Each such view is a tower describing the object from a particular (user) perspective. These views modularize the information according to the different ways in which it may be accessed by different reader groups.