|
The DASL Programming Language (Distributed Application Specification Language) is a high-level, strongly typed programming language originally developed at Sun Microsystems Laboratories between 1999 and 2003 as part of the (Ace Project ). The goals of the project were to enable rapid development of web-based applications based on Sun's J2EE architecture, and to eliminate the steep learning curve of platform-specific details. DASL defines an application as a domain model with one or more logical presentation models, where a logical presentation model consists of a choreography of the domain model objects described in a set of forms with attached actions. DASL generates the graphical user interface directly from the logical presentation. DASL is unique among modern application programming languages in its ability to generate a modern graphic user interface for an application without requiring the programmer to define the user interface explicitly, while allowing the programmer to control the look and feel of the generated graphic user interface. The DASL language is partially declarative and partially procedural. Description of object/data structures and persistence, and the description of the logical presentation, are declarative. Basic object constraints and behavior are declarative, while additional object behaviors are specified procedurally as methods. Queries can be defined either declaratively or by writing methods. The language and development environment are a practical realization of the model-driven architecture (MDA) approach. The programmer uses DASL to produce the platform-independent model or PIM, and the language code generators automatically produce and deploy the platform-specific model or PSM. New PSMs may be introduced by writing new code generators. ==Benefits of the approach== A key benefit of the DASL language approach over 3rd generation (3GL) programming languages is that enterprise applications can be specified in a very concise and precise way that expresses the application logic clearly. A small enterprise application in DASL can typically be implemented in 8-10K lines of DASL code, which the DASL compiler then typically translates into 200K lines of Java, XML, SQL, and other implementation artifacts. The 200K line figure is typical of equivalent applications written using 3GLs. The conciseness of DASL can be seen also in terms of the content of the two representations (DASL vs. the generated application code in Java/XML/SQL etc.). Most of the DASL code describes business logic and business processes specific to the application, independent of the deployment middleware, frameworks, and presentation mechanisms. This core business logic typically represents only 2-5% of the generated application code. Thus, writing, understanding, and maintaining the application code is much easier at the DASL level than it is at the level of the generated code, in which the business logic is scattered within various implementation artifacts. Another advantage of using DASL to write applications, rather than conventional 3rd generation languages and IDEs is that the DASL code is independent of middleware, GUI presentation frameworks, network topology, and other implementation technologies. As new middleware and frameworks are developed and evolve, existing DASL programs can be migrated to them without the need to re-implement them. For example, the original DASL code generators produced traditional HTML screens. Later, DASL code generators were written to use frameworks such as Apache Struts, and technologies such as JavaScript in the browser, to produce a more interactive experience. Today, new DASL generators being written that produce Rich Internet applications. Existing DASL applications can thus be converted to rich internet applications by recompiling them with the latest code generators. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Distributed Application Specification Language」の詳細全文を読む スポンサード リンク
|