Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Multitier programming
Multitier programming (or tierless programming) is a programming paradigm for distributed software, which typically follows a multitier architecture, physically separating different functional aspects of the software into different tiers (e.g., the client, the server and the database in a Web application). Multitier programming allows functionalities that span multiple of such tiers to be developed in a single compilation unit using a single programming language. Without multitier programming, tiers are developed using different languages, e.g., JavaScript for the Web client, PHP for the Web server and SQL for the database. Multitier programming is often integrated into general-purpose languages by extending them with support for distribution.
Concepts from multitier programming were pioneered by the Hop and Links languages and have found industrial adoption in solutions such as Ocsigen, Opa, WebSharper, Meteor or GWT.
Multitier programming provides a global view on the distributed system. This aspect has been shown similar to other programming paradigms such as choreographic programming, macroprogramming, and aggregate computing.
The code of the different tiers can be executed in a distributed manner on different networked computers. For instance, in a three-tier architecture, a system is divided into three main layers – typically the presentation, business, and data tiers. This approach has the benefit that by dividing a system into layers, the functionality implemented in one of the layers can be changed independently of the other layers. On the other hand, this architectural decision scatters a cross-cutting functionality belonging to several tiers over several compilation units.
In multitier programming, the different tiers are implemented using a single programming language. Different compilation backends take into account the destination tier (e.g., Java for a server and JavaScript for a web browser). Consequently, a functionality that is spread over tiers can be implemented in a single compilation unit of a multitier program.
At their core, multitier languages allow developers to define for different pieces of code the tiers to which the code belongs. The language features that enable this definition are quite diverse between different multitier languages, ranging from staging to annotations to types. The following example shows an Echo client–server application that illustrates different approaches. In the example, the client sends a message to the server and the server returns the same message to the client, where it is appended to a list of received messages.
Hop uses staging to embed code that is to be run on the client into a server-side program: Using the ~{…} notation, the code for the onload (Line 4) and onclick (Line 10) handlers is not immediately executed but the server generates the code for later execution on the client. On the other hand, the ${…} notation escapes one level of program generation. The expressions hop.port (Line 5), event.data (Line 6) and input (Line 9 and 10) are evaluated by the outer server program and the values to which they evaluate are injected into the generated client program. Hop supports full stage programming, i.e., ~{…} expressions can be arbitrarily nested such that not only server-side programs can generate client-side programs but also client-side programs are able to generate other client-side programs.
HTML can be embedded directly in Hop code. HTML generated on the server (Line 2–14) is passed to the client. HTML generated on the client can be added to the page using the standard DOM API (Line 6). Hop supports bidirectional communication between a running server and a running client instance through its standard library. The client connects to the WebSocket server through the standard HTML5 API (Line 5) and sends the current input value (Line 10). The server opens a WebSocket server (Line 17) that returns the value back to the client (Line 20). So-called services, which are executed on the server and produce a value that is returned to the client that invoked the service. For example, the echo service (Line 1) produces the HTML page served to the web client of the Echo application. Thus, the code in a service block is executed on the server.
Hub AI
Multitier programming AI simulator
(@Multitier programming_simulator)
Multitier programming
Multitier programming (or tierless programming) is a programming paradigm for distributed software, which typically follows a multitier architecture, physically separating different functional aspects of the software into different tiers (e.g., the client, the server and the database in a Web application). Multitier programming allows functionalities that span multiple of such tiers to be developed in a single compilation unit using a single programming language. Without multitier programming, tiers are developed using different languages, e.g., JavaScript for the Web client, PHP for the Web server and SQL for the database. Multitier programming is often integrated into general-purpose languages by extending them with support for distribution.
Concepts from multitier programming were pioneered by the Hop and Links languages and have found industrial adoption in solutions such as Ocsigen, Opa, WebSharper, Meteor or GWT.
Multitier programming provides a global view on the distributed system. This aspect has been shown similar to other programming paradigms such as choreographic programming, macroprogramming, and aggregate computing.
The code of the different tiers can be executed in a distributed manner on different networked computers. For instance, in a three-tier architecture, a system is divided into three main layers – typically the presentation, business, and data tiers. This approach has the benefit that by dividing a system into layers, the functionality implemented in one of the layers can be changed independently of the other layers. On the other hand, this architectural decision scatters a cross-cutting functionality belonging to several tiers over several compilation units.
In multitier programming, the different tiers are implemented using a single programming language. Different compilation backends take into account the destination tier (e.g., Java for a server and JavaScript for a web browser). Consequently, a functionality that is spread over tiers can be implemented in a single compilation unit of a multitier program.
At their core, multitier languages allow developers to define for different pieces of code the tiers to which the code belongs. The language features that enable this definition are quite diverse between different multitier languages, ranging from staging to annotations to types. The following example shows an Echo client–server application that illustrates different approaches. In the example, the client sends a message to the server and the server returns the same message to the client, where it is appended to a list of received messages.
Hop uses staging to embed code that is to be run on the client into a server-side program: Using the ~{…} notation, the code for the onload (Line 4) and onclick (Line 10) handlers is not immediately executed but the server generates the code for later execution on the client. On the other hand, the ${…} notation escapes one level of program generation. The expressions hop.port (Line 5), event.data (Line 6) and input (Line 9 and 10) are evaluated by the outer server program and the values to which they evaluate are injected into the generated client program. Hop supports full stage programming, i.e., ~{…} expressions can be arbitrarily nested such that not only server-side programs can generate client-side programs but also client-side programs are able to generate other client-side programs.
HTML can be embedded directly in Hop code. HTML generated on the server (Line 2–14) is passed to the client. HTML generated on the client can be added to the page using the standard DOM API (Line 6). Hop supports bidirectional communication between a running server and a running client instance through its standard library. The client connects to the WebSocket server through the standard HTML5 API (Line 5) and sends the current input value (Line 10). The server opens a WebSocket server (Line 17) that returns the value back to the client (Line 20). So-called services, which are executed on the server and produce a value that is returned to the client that invoked the service. For example, the echo service (Line 1) produces the HTML page served to the web client of the Echo application. Thus, the code in a service block is executed on the server.