Current Software Structure and Capabilities

W-KLIC is composed by a collection of KLIC modules which provide powerful high-level programming capabilities to access and manipulate information on the Internet.

The modules in W-KLIC provide a programming layer which allow access to the most important interfaces to fetch and exchange data over the Internet.

The current version of W-KLIC offers the ability to embed in KLIC programs access to the most basic Internet protocols: HyperText Transfer Protocol (HTTP), Common Gateway Interface (CGI), and Common Client Interface (CCI). W-KLIC contains different modules which provide access capabilities to the basic protocols adopted for exchange of data over the Internet as well as communication with existing browsers and other Internet related tools.

• HTTP Interface: W-KLIC offers a module http which allows basic access to communication via HTTP. The module offers predicates to send requests using HTTP protocol and obtain responses---in the format of strings of characters. Auxiliary predicates have been developed which allow interconversion between C strings and KLIC strings---a necessary feature for the implementation of the HTTP module. Implementation of this feature has been necessary since no equivalent capability is reported in the KLIC documentation.

• HTML Access: The modules html and tohtml allow KLIC programs to perform high-level management of HTML documents. These modules supply predicates which allow conversion of string representing (part of) HTML documents into KLIC terms and vice-versa. The term representation of HTML documents allows easy generation of HTML documents within KLIC program, without relying on unnatural string manipulation operations. Viceversa, the predicates in this module allows to convert string-based representations of HTML documents (e.g., obtained from the Internet using the http access) to term representations. Term representations of HTML documents allows incremental construction of HTML documents during program execution.

• CGI Access: The module parse_hidden allows the parsing the string of name-value pairs which are communicated to a Common Gateway Interface (CGI) script. The predicates in this module allow to obtain a list of pairs from a string produced by the HTTP server in reply to a CGI connection. The successive level of the CGI management is currently only partially supported. Execution of communication via CGI requires two components: (i) ability, within the server, to accept data incoming from browsers which are activating a CGI communication; (ii) ability to transfer data from the browser to the server. A sufficiently general gateway script is presented in the module cgi_copy, allowing transfer of data from browser to an existing server. The module server_copy contains a template to realize the server side component of CGI communication. It shows how to receive information from the gateway script, spawn a novel thread of computation to serve the new communication and return an output to the gateway script. It also shows how to allow using a predicate defined in the program as script to serve a program in a dynamically generated document. Embedding of these features in a separate collection of high-level generic constructs is currently in progress.

• CCI Access The module cci allows a KLIC application to communicate to any Common Client Interface compliant application. The current version of the CCI interface has been specifically designed to handle interactions with running sessions of NCSA Mosaic. The CCI interface allows the following activities:
  • connection to a running session of Mosaic;
  • tracking of the activities of such session---each URL visited can be captured and transmitted to the connected computation;
  • access to the data transferred to the Mosaic session;
  • filtering of the data transmitted to Mosaic---e.g., capture all the data belonging to a given MIME format and avoid their direct visualization in Mosaic;
  • forcing the Mosaic session to access and load URLs defined by the connected computation (and not by the user of the browser).