iTask as a New Paradigm for Building GUI Applications

Abstract

The iTask system is a combinator library written in Clean offering a declarative, domain-specific language for defining workflows. From a declarative specification, a complete multi-user, web-enabled, workflow management system (WFMS) is generated. In the iTask paradigm, a workflow is a definition in which interactive elements are defined by editors on model values (abstracting from concrete GUI implementation details). The order of their appearance is calculated dynamically using combinator functions (abstracting from concrete synchronisation details). Defining interactive elements and the order of their appearance are also major concerns when programming GUI applications. For this reason, the iTask paradigm is potentially suited to program GUI applications as well. However, the iTask system was designed for a different application domain and lacks a number of key features to make it suited for programming GUI applications. In this paper, we identify these key features and show how they can be added to the iTask system in an orthogonal way, thus creating a new paradigm for programming GUI applications.

Typelets — A Rule-Based Evaluation Model for Dynamic, Statically Typed User Interfaces

“…One strand of related work includes work on providing type-safe language bindings for constructing graphical user type leg = {legno: int; underlying: string option; fixedrate: float option; currency: currency} type tradedata = {tdata1: string; tdata2: string} type tlet = {tradeid: string; nominal: float; receiveleg: leg; payleg: leg; tradedata: tradedata} open Layout let leg = pick(.underlying) @@ pick(.fixedrate) @@ pick(.currency) let l2 : tlet t = pick(.tradeid) % pick(.nominal) @@ grp(box "Receive" (lift(.receiveleg)leg) % box "Pay" (lift(.payleg)leg)) @@ pick (.tradedata) interfaces in functional languages [3,19,14] either using monads or by using the effectful features of a language for controlling the behavior of a GUI. A specific monadic combinator library for constructing GUI's is the Clean iTask library [17,20], which primarily focuses on allowing the programmer to generate a workflow GUI from a declarative specification of the GUI and the workflow. Compared to the iTask framework, typelets do not address how windows are opened and closed, but rather on how fields, grids, and controls change upon changes in a field.…”

Defining Multi-user Web Applications with iTasks

“…In the parallel (line 5-6) the content is stored in the shared editor state, and initially just one task is created, the editor itself. With ActionSave, she can choose to save the current text (line 3), after which the text is stored to file and the editor is recursively called to allow to continue editing (line [14][15][16]. The update of the browser page is optimized such that such recursive calls are not visually noticeable to the end user.…”

“…-Tasks can become web applications including GUI elements like buttons, dialogues, windows and menus [15]. -The semantics of iTask combinators has been formally described [11,17].…”

Bridging the GUI gap with reactive values and relations

“…GuiTV [11], a Haskell implementation for type-based GUI generation, can construct widget compositions for functions, to provide the arguments and show A similar idea is used in iTask [31], a client-server, taskoriented, state-transforming web programming framework for Clean. iTasks seeks to address large-scale architectural GUI concerns, generating user interfaces automatically from types [2] and then rendering these to a browser.…”

“…There are some similarities between RVs and iTask's [31] Uniform Data Sources (UDS) [30], but UDS has no support for subscription to change notification. Further, a central aspect of iTask is automatic generation of GUIs from types with a particular focus on Web applications, whereas RVs and RRs provide generic, re-usable infrastructure for GUI programming and more.…”