Net.Data Programming Guide

Web Registry

The Net.Data Web registry is available on some platforms and provides persistent storage for application-related data. A Web registry can be used to store configuration information and other data that can be accessed dynamically at run time by Web-based applications. You can access Web registries only through Net.Data macros using Net.Data and the Web registry built-in support and from CGI programs written for this purpose.

Standard Web page development requires that URLs be placed directly in the HTML source for the page. This makes changing hyperlinks difficult. The static nature also limits the type of hyperlinks that can be easily placed on a Web page. Using a Web registry to store data related to an application, for example URLs, can help in the creation of HTML pages with dynamically set hyperlinks.

Information can be stored and maintained in a registry by application developers and Web administrators having write access to the registry. Applications retrieve the information from their associated registries at run time. This facilitates the design of flexible applications and also allows movement of applications and servers. Net.Data macros can be used to create HTML pages using dynamically set hyperlinks.

Information is stored in a Web registry in the form of registry entries. Each registry entry consists of a pair of character strings: a RegistryVariable string and a corresponding RegistryData string. Any information that can be represented by a pair of strings can be stored as a registry entry. The variable string is used as a search key to locate and retrieve specific entries from a registry.

You can see sample contents of a Web registry in Table 3.

Table 3. Sample Web Registry

CompanyName	WorldConnect
Server	ftp.einet.net
JohnDoe/foreground	Green
CompanyURL/IBM Corp.	http://www.ibm.com
CompanyURL/Sun Microsystems Corp.	http://www.sun.com
CompanyURL/Digital Equipment Corp.	http://www.dec.com
JaneDoe/Home_page	http://jane.info.net

Here are some reasons to consider using a Web registry:

• You can use a Web registry to store aliases for servers and URLs, facilitating the relocation of applications and servers.

• Application developers can ship their Web-based applications with data, such as URLs, predefined in the registry. The end user can modify the registry data to change the behavior of the application.

• A Web registry can be used to perform URL searches based on product name, national language, manufacturer, and so on.

Indexed entries in the Web Registry are entries whose RegistryVariable strings have an additional Index string appended to them, as in "RegistryVariable/Index". The user provides the value of the index string in a separate parameter to a built-in function designed to work with indexed entries. Multiple indexed registry entries can have the same RegistryVariable string value, but can maintain their uniqueness by having different Index string values.

Table 4. Sample Indexed Web Registry

Smith/Company_URL	http://www.ibmlink.ibm.com
Smith/Home_page	http://www.advantis.com

Even though the above two indexed entries have the same RegistryVariable string value "Smith", the index string is different in each case. They are treated as two distinct entries by the Web registry functions.