As mentioned previously, many early screen-scraping products supported the HLLAPI or EHLLAPI specification.
While tedious, using an HLLAPI-based tool kit made it possible to achieve quick results, and many HLLAPI applications have been deployed to integrate legacy processes.
Unfortunately, HLLAPI applications require more effort to maintain than to develop and, over time, tend to devolve to a less maintainable state.
The rigid binding of the HLLAPI client to the legacy terminal session server can lead to instability when the application is deployed in a production environment.
It is desirable, however, to replace the procedural HLLAPI code with a layer that isolates and uncouples the legacy application specific component from the client application .