Contents in Current Page:

1. Canto - Introduction (P0049)
2. Canto - Data model
3. Canto - Nodes
4. Canto - Hierarchical structure
5. Canto - Links

Canto - Introduction (P0049)

The Canto hypertext data model is characterized by a hierarchical schema mechanism that allows a predetermined, open-ended schema to be embedded in the hyperdocument. Canto uses two types of nodes: Concept nodes which provide  organizational structure, and information nodes which contain test and other data. The operations provided by Canto data model are defined formally using Z. The  Canto schema Language gives the hypertext designer access to these operations.

Canto - Data model

 The Canto Hypertext data model was designed to serve as a basis for a hypertext system into which data can easily be placed, located or removed without the user becoming disoriented. The key idea in Canto is an integrated hypertext schema. The schema is a decsription of the data and a specification of of the attributes and the relationships among the data types. In Canto a Hypertext application consistsof three entities. HT = Nc is a set of concept nodes representing the structures. Ni is a set of Information nodes containing information. L is a set of implicit and explicit links. Concept nodes contain a key phrase that identifies the information stored in the corresponding portion of the structure. A subtree of related ideas can be aggregated under a single concept node. Concept nodes also contain explicit links to other nodes. Data is contained in linear linked lists of information nodes, where each list is owned by a specific concept node. Information nodes hold the data in an application specific format. A concpet node may or may not not have information nodes associated with it. Information nodes associated with concept  nodes expected to contain data relating to the topic implied by the concept node's key phrase.

Canto - Nodes

 There are two type of nodes in Canto: concept nodes to contain the ideas and subideas and provide organizational structure , and information nodes to contain the data. Concept nodes contain a key phrase that identifies the information stored in the corresponding portion of the structure. A subtree of related ideas can be  aggregated under a single concept node. Concept nodes also contain explicit links to other nodes. Data is contained in linear linked lists of information nodes, where each list is owned by a specific concept node. Information nodes hold the data in an application specific format. A concpet node may or may not not have information nodes associated with it. Information nodes associated with concept nodes expected to contain data relating to the topic implied by the concept node's key phrase. Concept nodes can be embedded in a Canto Hyperdocument in two ways: 1. they can be installed in the most basic hypertext model, i.e, nodes and links. Additional hypertext features , such as node aggregates can be simulated with concept nodes, or adde to the model as a new type of object. 2. They can also ne  installed in more elaborate models like Dexter or Trellis applying the schema on top of existing models.

Canto - Hierarchical structure

In Canto's hierarchical structure, users access information much like they would in an outline progressing through the main ideas until the desired concept is found. This is a familiar process to most people and translates well into a hypertext system. The hierarchical structure is maintained through a system of implicit links between concept nodes.

Canto - Links

In Canto Links may be either implicit or explicit. Implicit Links are derived from the structure and order of the nodes. Implicit links connect nodes to other concept nodes, or to information nodes. Explicit links may connect any two nodes and are used to represent non-hierarchical relationships.