public interface PlatformDependencies
Barring ActiveX being disabled, the XMLHttpRequest object is available to Smart GWT on all supported browsers and an XML parser is available on all supported browsers except Safari versions prior to 3.0.3.
 Smart GWT client-server communication is not affected by the lack of an XML parser or the
 XMLHttpRequest object, but the xmlHttpRequest transport will not be available if
 the XMLHttpRequest object is not available.  Instead, the hiddenFrame or the
 scriptInclude transports are used for client-server communication. 
XML Parser
 If an XML Parser is not available to Smart GWT, all client-side web service
 bindings and related methods will be unavailable.  Turning off ActiveX disables integration
 paths 2 and 3 in the diagram below.  If you want to bind to web services and require deployment
 to IE without ActiveX (or you need to support Safari pre 3.0.3), you'll need to do all XML
 processing on the server and use either the Smart GWT DSRequest or JSON operation pathways
 (integration paths 1 and 4 in the diagram below).  See the discussion in ClientServerIntegration for more information on the integration paths
 shown in the diagram below. 
 You call XMLTools.nativeXMLAvailable() to check
 for the availability of a native XML parser at runtime. 
  
 
XMLHttpRequest
 The XMLHttpRequest object is used
 for the xmlHttpRequest RPCTransport. Safari,
 Mozilla, Firefox, and IE 7 provide a native XMLHttpRequest implementation that is not affected
 by ActiveX being disabled (although the native IE 7 implementation can still be explicitly
 disabled by the end user).  IE 5.5 and IE 6.0 rely on the ActiveX bridge to support
 XMLHttpRequest, so if ActiveX is disabled in these browsers, XMLHttpRequest will not be
 available. 
 The lack of the XMLHttpRequest objects affects UI loading features like ViewLoader, and HTMLFlow when
 used in remote loading mode (via HTMLFlow.contentsURL, HTMLFlow.setContentsURL(), but does not affect the typical client/server communication
 pathways (integration paths 1 and 5 in the diagram above). 
 Also affected are low level
 features RPCRequest.serverOutputAsString, RPCRequest.evalResult, and RPCResponse.httpResponseCode. 
 In all of the above cases, it is possible to use the
 hiddenFrame transport to support these features when XMLHttpRequest is not
 available.  Smart GWT will automatically send the request using the hiddenFrame
 transport when it detects that XMLHttpRequest is unavailable.  To support the above features,
 you'll need to use the RPCManager APIs on the server to send back the data that would normally
 be returned by XMLHttpRequest.  Since XMLHttpRequest cannot target URLs outside of the current
 domain, this strategy applies also to using the above features with cross-domain URLs. 
 You
 can call RPCManager.xmlHttpRequestAvailable() to check for the availability of XMLHttpRequest at
 runtime.