The page-level web functions focus on Web pages rather than on single documents. A high-speed HTML parser enables the Web replay engine to access hyperlinks, forms and other load-relevant elements while downloading HTML documents. The functions also download embedded documents like images, applets and frames automatically.
One of the most important benefits of parsing HTML is direct access to session IDs that may reside in query strings of URLs or in hidden fields of forms. However, for sake of speed and memory overhead, HTML elements that are not relevant for navigation or data entry are ignored by the parser. This means that you can query the HTML document for hyperlinks, but in order to access HTML tables you still need to use the WebParseResponseData function.
When to use the page-level web functions :
When your Web pages contain dynamically embedded documents, for example, ad banner rotators.
When you do not want to care about session handling or when pages contain lots of session information that would require many WebParseResponseData function calls to maintain the session during replay.
When your server requires the “referrer” header to be set dynamically.
When your load balancer redirects the client to different servers dynamically.
When you want to use automatic verification for a page that checks whether the context between pages can be maintained.
For shorter, easy-to-read scripts.
When to use the low-level web functions instead:
When you need to generate the highest possible load on your server (number of virtual users, throughput)
When your Web pages use lots of client-side scripting, for example, JavaScript, VBScript, in order to download further documents or cause page transitions.
When your application is not Web-browser-based, for example, multimedia clients that use HTTP for communication but do not use HTML.
When maintaining context between pages is not relevant.
The Web page context is the link used to navigate from one page to another. The context can be maintained if there is enough HTML hyperlink information in page A to navigate to page B. Thus the context-less page-level web functions use an absolute URL to request a Web document, whereas the contextual functions try to retrieve the URL from the prior Web page. If a contextual function fails to find the necessary hyperlink information, the context is lost and all subsequent page download requests may also fail.