Remote Application Platform (RAP, formerly "Rich Ajax Platform") Project is an open-source software project under the Eclipse Technology Project which aims to enable software developers to build Ajax-enabled rich Internet applications by using the Eclipse development model, plugins and a Java-only application programming interface (API).
 It can be considered a counterpart for web development to the Rich Client Platform (RCP).
 The API is very similar to RCP so developers who know RCP can reuse extant knowledge.
 RAP encourages sharing source code between RCP and RAP applications to reduce the development effort for business applications that need both desktop-based and web-based front ends.
ProcessWire is a free and open source content management system (CMS), content management framework (CMF) and web application framework (WAF) written in the PHP programming language.
 It is distributed under the Mozilla Public License 2.0.
 ProcessWire is built around an API with usage and naming conventions similar to the JavaScript framework jQuery.
 The stated goal behind the API is to provide the level of accessibility and control to pages in a website that jQuery provides to the DOM.
 Content is managed either via the API or the web-based admin control panel.
 ProcessWire is largely used for development of web sites, web applications, services, content feeds and related applications.
Visual Basic is a third-generation event-driven programming language and integrated development environment (IDE) from Microsoft for its Component Object Model (COM) programming model first released in 1991 and declared legacy during 2008.
 Microsoft intended Visual Basic to be relatively easy to learn and use.
 Visual Basic was derived from BASIC, a user-friendly programming language designed for beginners, and it enables the rapid application development (RAD) of graphical user interface (GUI) applications, access to databases using Data Access Objects, Remote Data Objects, or ActiveX Data Objects, and creation of ActiveX controls and objects.
OPOS, full name OLE for Retail POS, a platform specific implementation of UnifiedPOS, is a point of sale device standard for Microsoft Windows operating systems that was initiated by Microsoft, NCR, Epson, and Fujitsu-ICL and is managed by the Association for Retail Technology Standards.
 The OPOS API was first published in January 1996.
 The standard uses component object model and, because of that, all languages that support COM controls (i.e. Visual C++, Visual Basic, and C#) can be used to write applications.
Global Address Space Programming Interface (GPI) is an application programming interface (API) for the development of scalable, asynchronous and fault tolerant parallel applications.
 It is an implementation of the partitioned global address space programming model.
The Linux kernel provides several interfaces to user-space applications that are used for different purposes and that have different properties by design.
 There are two types of application programming interface (API) in the Linux kernel that are not to be confused: the "kernel–user space" API and the "kernel internal" API.
Visual DialogScript (VDS) is an interpreted programming language for Microsoft Windows.
 It can be used to create small, fast programs.
 VDS has a large number of dialog and graphical elements available to create professional looking programs.
 VDS programs have access to the Windows API; therefore, it is possible to write applications that can perform the same advanced tasks as other programming languages such as Visual Basic, C++, or Delphi.
The Native API (with capitalized N) is a lightweight application programming interface (API) used by Windows NT and user mode applications.
 This API is used in the early stages of Windows NT startup process, when other components and APIs are still unavailable.
 Therefore, a few Windows components, such as the Client/Server Runtime Subsystem (CSRSS), are implemented using the Native API.
 The Native API is also used by subroutines such as those in kernel32.dll that implement the Windows API, the API based on which most of the Windows components are created.
MillWheel is a framework for building low-latency data-processing applications that is widely used at Google.
 Users specify a directed computation graph and application code for individual nodes, and the system manages persistent state and the continuous flow of records, all within the envelope of the framework's fault-tolerance guarantees.
 This paper describes MillWheel's programming model as well as its implementation.
 The case study of a continuous anomaly detector in use at Google serves to motivate how many of MillWheel's features are used.
 MillWheel's programming model provides a notion of logical time, making it simple to write time-based aggregations.
 MillWheel was designed from the outset with fault tolerance and scalability in mind.
 In practice, we find that MillWheel's unique combination of scalability, fault tolerance, and a versatile programming model lends itself to a wide variety of problems at Google.
JWt (pronounced "jay-witty") is an open source widget-centric web application framework for the Java programming language developed by Emweb.
 It has an API that uses established GUI application development patterns.
 The programming model is component-based and event-driven, similar to Swing.

Question: What programming model first released in 1991 can be used to write applications for the OPOS API?
Answer: Visual Basic