CML Web Page Technologies

The CML application uses the following Web page technologies:

• Active Server Pages (ASP) is the foundation of the CML Web application. ASP is an interpreted application environment for generating HTML pages using scripts. An ASP document can contain HTML and script. ASP provides a set of objects we can manipulate using VBScript or JScript.

  As described in the preceding section, the CML application uses an ASP page for each discrete task. An ASP page can correspond to a page the user sees, but more frequently each page the user sees is the result of executing the script in several ASP files, using server-side includes and IFrames.

  The appearances of the Web pages are altered and the pages are redisplayed using multiple divisions (HTML <DIV> tags) on the ASP page. This process is transparent to the user. Using <DIV> Tags in the CML describes how DIV sections are used in the library application.

  Intrinsic Objects and Active Server Pages in the CML describe the use of built-in ASP objects and the scripting of the CML ASP pages.

• Server-side include (SSI) directives are used to leverage the use of code modules that are repeated throughout the application. The CML application makes extensive use of the SSI directive (#include). An example of an ASP file used with #include is Navigation.asp. This page is called from all the CML Web pages that display the orange navigation bar. The advantage of SSI is that a change to the code module is easy to implement throughout the application. Starting the CML Application and Searching for Library Materials describe the use of server-side includes in the CML application.
• Cascading style sheets (CSS) are used extensively by the CML site. Defining and using styles for elements that are used repeatedly in the application Web pages will ensure a consistent look throughout the application. For example, when property names and their values, such as BACKGROUND: steelblue, COLOR: white, and FONT-SIZE: xx-small, are defined for the BUTTON element then the BUTTON is white with a steel-blue background and uses the xx-small font throughout the application. The cascading style sheet for the CML application is named theme.css. The Library ASP page uses theme.css.

  About Sub_menu.asp describes how the CML application uses cascading style sheets.

• IFRAME is an HTML tag that delimits a floating or inline frame (hence the name IFrame). IFrames are used on many CML pages. Think of the IFrame as a window to another ASP page; it is a way to execute an additional piece of code. Using IFrames in the CML describes how IFrames are used in the CML application. The advantage of the IFrame is the ability to conditionally execute the code of the ASP page specified in the IFrame. The use of an IFrame allows the application to spawn a new request to the server.
• Dynamic HTML (DHTML) allows a Web page to change in appearance and functionality without a roundtrip to the server to refresh the page. DHTML enables data binding on a Web page and makes possible animation and movement of any element on a Web page.
• Remote Data Service (RDS) is a high-performance client-side data caching technology that brings database connectivity to Web-based applications. RDS is implemented on the client in the Search and Checkout modules of the CML application to facilitate client-side sorting. Some pages have multiple RDS controls, each control hosting a recordset. The recordsets are assembled into a table that is displayed on the Web page. Overview of RDS and Using RDS ActiveX Controls describe how RDS is used in the CML application.

Before DHTML and RDS, it was not possible to sort information on a Web page. To display information in a different sort order the database was requeried, specifying a different sort. Each new sort necessitated another roundtrip to the server.

The alternative to RDS is static HTML pages and XML.