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1.1.1 Dynamic Structure


The structure of Hyperwave Information Server is dynamic, displaying as a flexible hierarchy of objects represented by folders and icons. The dynamic nature of Hyperwave Information Server is what makes it such an efficient solution for information management.

Hyperwave Information Server eliminates problems of static structure by the introduction of structural elements and an object repository.

1.1.1.1 Structural Elements

The structural elements on the Hyperwave Information Server are called collections. A collection contains a number of other elements, which could be documents or other collections. There are also a number of types of collection, which have particular attributes or behave in a certain way. These are Collection, Sequence, Language Cluster, MultiCluster, and AlternativeCluster. For more information on collection types, see page 116.

Figure 1 shows a simple collection. A collection is very much like a directory or folder in a hierarchical file system. However, on the Hyperwave Information Server, an item may be a member of more than one collection (such as the text item in Figure 1). When you access a collection (with a URL), it is displayed as a menu-like table of contents, i.e. the user is given a choice of sub-elements. Of course the sub-elements could again be collections. This is what is called the collection hierarchy.

Figure 1: The Collection structure element

1.1.1.2 Structural and Referential Hyperlinks

Hyperwave Information Server differentiates between structural and referential hyperlinks, ensuring the structural links are maintained automatically by the server. Authors need only be aware of referential links, giving them more time to concentrate on content.

1.1.1.3 Documents, Objects, Attributes

Unlike many other Web-based systems, Hyperwave Information Server stores its documents not just as plain files in a file system, but in an object-oriented repository (a kind of database). Also stored in the repository are information objects. These objects carry metadata about documents on the server. Metadata is stored in the form of attribute name and value pairs, e.g. Title=Company Report (where Title is the attribute name and Company Report is the value).

Documents on the Hyperwave Information Server can be of any type.

The list of attributes is extensible, in that you can create attributes to suit your particular information management needs. We may classify attributes into the following groups:

TYPES OF ATTRIBUTES

Figure 2: Modify A ttributes dialog box
The ability to define arbitrary attributes (metadata) for all kinds of objects prepares Hyperwave Information Server for many applications, which would otherwise require the functionality of a relational database. For more information on Attributes, see page 139.

EXAMPLE

A typical example, found in almost any intranet, is an employee directory. Every employee in the directory is represented by an object with user-defined attributes such as Lastname, Firstname, Middlename, Phone, Fax, Email, and Department, which are all indexed and thus searchable. The objects are inserted into a collection with a modified search dialog, which lets you search for combinations of the above attributes. For a better implementation, rather than inserting all employees into one large collection, you could have a collection hierarchy representing the company hierarchy, with one collection for every department. In this way, users could browse the directory instead of searching, if they preferred. The employee objects could also be documents or MultiClusters (see page 136), so that you could offer additional information (e.g., pictures, work descriptions) for each employee.

1.1.1.4 Separate Information and Presentation

Another important feature that comes with the use of structural elements in the Hyperwave Information Server is the clear separation of information (content) and its presentation (layout, navigation). The document management community has traditionally separated content and layout (just think of the concepts of SGML and now XML, where the document defines the content and a style sheet defines the layout). This distinction is not possible in static HTML documents, since HTML defines both content and its presentation (including navigation).

Hyperwave Information Server lets authors focus on supplying the content: the presentation (with layout and navigation) is performed by the system, according to the exact specifications of system administrators.

ADVANTAGES

What are the advantages of having content and presentation separated?

More information about customizing the user interface can be found in the Hyperwave Programmer's Guide.

CONSISTENCY

The collection listing is dynamically generated by the system. This means that it is always consistent. When you delete something, the corresponding entry or entries are also removed. When you insert something into a collection, its entry appears in the collection listing. Since information objects inserted into Hyperwave Information Server's repository always have to be put into at least one collection, there can be no orphaned objects.

REDUCED MAINTENANCE EFFORT

All this is done with simple insert and delete operations. There is no need to manually maintain a table of contents, and no opportunity to make a mistake in doing so, such as forgetting to update a link when you move an object.

SECURITY

Unlike in a hypertext model (Figure 3), there is no need to edit other people's documents in order to insert a new document. This allows for a strong security model that supports collaborative authoring.

NAVIGATION

While it is possible to override the collection's automatic table of contents menu with a manually designed page, the majority of a large Web site's collections will use the automatically generated collection listings in order to reduce the overall graphic design work required. For the users this means a consistent way of navigating the hierarchy.

In addition, Hyperwave Information Server also supports a tree-like navigation of the collection hierarchy (similar to the Windows Explorer). This makes it very easy to navigate the collection hierarchy (and also to manipulate it, if you have the appropriate access rights).

MULTIPLE VIEWS

The collection hierarchy can also be seen as a classification of the information in the system. Since a document or collection may be member of a number of collections, such a classification need not be unique. There can be multiple views (classifications) of the same information space. After all, why should a company's top management have the same view as a specialized employee?

SCOPE

The collection hierarchy in Hyperwave Information Server provides the ability to define scope in terms of the logical structure of the information space. For example, we may specify that a certain search operation should be restricted to a certain part of the information space, i.e. only documents in a certain collection. Likewise, we can use the scope to perform arbitrary operations on a certain part of the information space, or to define access permissions.

HIGHLY DYNAMIC

The collection listing is not modified when you insert an element. Instead, the listing is generated dynamically when a user accesses the URL associated with the collection. When the collection listing is dynamically created, such things as the collection sort order, the identity of the user and their preferences, and the validity of the member item are taken into account. Sort order simply refers to how a collection is sorted: by title, creation date, etc. Only items to which the user has rights will be listed; some objects may only be accessible at certain times (otherwise they are invisible). Essentially, this means that for different users the collection listing may look different at any one time.

REUSABLE COMPONENTS

Of course, it now becomes possible to re-use certain parts of the collection hierarchy in many different places. For example, in a Web Based Training application, parts of a lesson may appear in multiple lessons. Still, they are not physical copies, but the very same items.


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