Background
Active Server Pages (ASP) is a scripting technology developed by Microsoft Corporation and is based on the server side, contrary to other scripting approaches that are integrated on web-based applications that are based on the client side. Scripting is one of integral technologies used in the development of web services. An example is Java script, which is client based (Francis, 1998). The ASP facilitates the creation of web -based applications and services that are dynamic and incorporates some interactive elements. A basic structure of an ASP page comprises of a Hyper Text Mark-up Language (HTML) page that has server-side page scripts, which run on a web server before it is sent to a web browser application.
ASP is combined with other platforms such as the Component Object Model (COM), HTML, and Extensible Mark-up Language to develop web services that are more user-interactive compared to other scripting technologies (Francis, 1998). Scripts that are based on the server are usually executed when a web browser application requests for an .asp file from the web server. The web server usually responds to the requests through executing the commands in the script. The web server then transforms into a standard format for a web page, after which it sends it to the user (Shaw, 2003).
ASP scripts used in the development of web services can be extended using COM and XML components. COM components provide a platform through which the scripts can be reused and made compact. In addition, they provide a secure means through which information can be accessed. Automation is a significant concept during the implementation of a scripting technology (Mitchell, 2000). On the other hand, ASP scripts that have been extended using XML deploy the use of a mark-up language that formats the data in a structured manner, through the use of tags. ASP was originally developed as an add-on that functioned under the Windows NT 4.0 platform through the Internet Information Services.
Later developments saw its integration into the server operating systems of Microsoft Corporation as a free component (Francis, 1998). The ASP used the .asp file extension. Active Server Pages under the ASP.NET platform use the .aspx file extension. ASP.NET is supported only on the.NET framework of Microsoft (Strahl, 2002). The.NET framework is faster and can robust scripting commands compared to the classic ASP. The development of ASP.NET was based on the frameworks of the classic ASP (Francis, 1998).
Introduction
This research paper attempts to provide an insight into understanding of the ASP scripting technology and its relationship with the development of web services. It provides an outline of the history of the ASP technology, the basics of the ASP technology, the functions of the ASP technology, ASP versions and their applications, strengths and limitations of the ASP technology, and finally providing a summary concerning the use of ASP as a scripting technology.
History of the ASP Technology
The development of the ASP was during the mid 90’s and was aimed at the creation of web services that are subject to change according to the users’ demands and interactions (Francis, 1998). This is helpful during the storage of information that is specific to a particular user. The underlying concept during the development of the ASP was to facilitate what was is called the dynamic web content (Mitchell, 2000); implying that a web service and its respective application is intelligent enough to learn data such as the frequent visitors of a web page, and their matching credentials after which it could store and retrieve them when needed.
For instance, in a business context, such an approach is effective in the management of passwords and login information such as user names. It is also important in applications that require updating after very short periods such as news events (Mitchell, 2000).
The original ASP was developed using the concepts of the dbWeb and iBasic tools (Mitchell, 2000), which were developed by the Aspect Software Engineering (Strahl, 2002). ASP can therefore be said to be one of the first web-based application environments that executed directly on the server, rather than on the client side. This was during 1996, nine months after Apple (which called NeXT by the time) released its web development application called WebObjects (Morneau & Batistick, 2000).
The main objective behind the development of WebObjects was to develop a high performance scripting technology approach compared to the CGI scripts that were being used during the time. The calling of external applications was also not effective and did not exhibit high performance. As a result, this led to the development of classic ASP (Shaw, 2003).
The Internet Information Server 3.0 and other applications that were used for hosting web servers on a windows framework installed the need to develop a web page that could change as per user commands and had the ability to incorporate the concept of dynamic web content. The first approach towards the solution of this problem was the development of the ASP (Strahl, 2002). The original ASP used the Virtual Basic (VB) programming language to execute scripting commands. This was ASP version 1.0, and was created during December 1996 by Microsoft Corporation. Prior to the development of ASP version.01, web developers relied on integrating programming languages and scripts in developing web applications that had to be loaded for them to be able to implement web services that were dynamic and interactive.
This was slow on a significant number of windows based servers, and caused performance issues on the servers. As a result, Microsoft Corporation saw the need to develop a scripting technology that facilitated the creation dynamic web services with little performance constraints on their servers. In order to implement this, Microsoft had to develop a scripting technology that could be executed directly via the server, without having the need to load external programs that are client based (Morneau & Batistick, 2000). The ASP provided an effective solution to these server constraints that were associated with performance issues. The execution of components in ASP was done directly in the website, via a web browser through the ActiveX technology, which was used to build single components (Francis, 1998).
ASP and the development of web services
A web service is one of the elements of a web server, which an end-user on the client side can call using http requests. A web service can be defined as an application that can be accessed using standard web communication protocols such as HTTP, Simple Object Access Protocol (SOAP) and SNMP. The various protocols are majorly used for transport while the backend code is used in the development of ASP web services.
ASP provides a framework through which the web developer can develop web services that are custom that the user can request using various client applications. ASP can support the development of XML web services, WCF services and Web references developed in Visual Studio. An XML web service is used to offer a specific functionality element to web content developed using internet standards that bases on HTTP and XML. A significant characteristic of ASP that makes it suitable for development of web services is its ability to offer frameworks for authentication and state management. It is also important to note that web services developed using ASP is interoperable across all messaging platforms on the client side.
Web services developed using ASP has features that can be used to implement the various types of authentication, user roles and properties of their profiles. ASP web services form an integral fragment of the Service Oriented Architecture, whereby the server provides access to different web services. An essential characteristic of the web services developed using ASP is that they can support different client applications and services. The various client applications that can support ASP web services are AJAX clients,.NET Framework clients and SOAP clients.
There are several approaches for consuming web services implemented using the ASP framework. It is important to note that any platform that can communicate with SOAP clients have the capability of communication with web services implemented in ASP. Most web services implemented in the same server use the same xml document with different back end code for the web service. Some of the ways in which web services are consumed include the use of Visual Studio.NET, command line tools and specific web browser features that facilitate remote scripting. The next section outlines the basics of web services development using the ASP framework.
Basics of the ASP technology
The ASP technology is basically a scripting strategy that aims at the development of more dynamic and interactive web services. There are two major components that are needed in the creation of an ASP; an HTML component and the Code Behind Page (Mitchell, 2000). The HTML component is primarily used in the development of visual representation of the web service (Francis, 1998).
There are diverse scripting languages that can be used in the development of ASP. The most commonly used scripting languages in the development of ASP include the VBScript and Jscript in its scripting engine. The scripting languages form an essential component of the ASP technologies. The scripting code can either be implemented using Jscript or VBScript (Morneau & Batistick, 2000).
The Microsoft Corporation uses the ASP as a basic framework for the development of Web backend logic. The scripting metaphor is an important concept in the development of the ASP that allows web developers and users to integrate HTML and code that has been scripted in order in a single document in order to create web content that is dynamic (Mitchell, 2000). The idea of scripting is not new to Microsoft and has been in existence for a long period of time. Development tools such as Cold Fusion had been implemented long before the scripting technology came to be implemented.
The VBScript is one of the active scripting languages that was created by Microsoft and implemented on a Visual Basic environment (Strahl, 2002). Its advantage for use in scripting is that it is lightweight and therefore offers a fast interpreter in Microsoft environments. Every desktop release of Microsoft comes with an in-built VBScript. An important aspect of the VBScript is that it uses the COM objects to access data in the environment that it is being run. VBScript is used to code functions that are executable and embedded in HTML web services (Francis, 1998). In addition, the scripting language is used for web page processing on the server side, in which case it is implemented using the <% and %> context switch statements (Strahl, 2002).
Jscript on the hand is implemented on the server side through the use of Windows Scrip engine. With development of the.NET framework, a new version of Jscript was developed, it was called Jscript.NET. Jscript is different from Java Script in the sense that it has additional features for conditional compilation. Just like VBScript, Jscript is implemented on a COM platform and it has the abilities to host web based applications on the server side.
With the dawn of ASP, Microsoft took the concept of scripting to another level through the creation of a scripting environment that could be integrated into the Windows operating system architecture and other extensions such as the COM. It is important to note that ASP is the development of the ISAPI, but in a more specific sense and eliminating the complexities associated with the early scripting platforms. The ASP serves to hide the complexity associated with the implementation of system interfaces and the protocols that are used in the client server communication (Mitchell, 2000). The implementation of an ASP engine is uses a server extension that is script mapped, with the driving engine being associated with dynamic linked libraries (dll), this result into ASP-dll, which is an extension of the ISAPI (Shaw, 2003).
The ISAPI extension is an important component of the ASP and is called every time a user tries to gain access to a web page having an .asp file extension. Script maps are stored on the server database, and they are used for redirecting the ASP scripts in the DLL. Script maps primarily serve as an avenue through which the ASP can execute automatically. The underlying principle is that the ASP.dll is usually besought for every .asp file in the server database.
The ASP.dll therefore hosts the two most important components of the ASP: the HTML parser and the scripting language interpreter, which can either be VBScript or Jscript interpreter (Morneau & Batistick, 2000). The HTML parser is responsible for the parsing of the HTML pages, evaluating the code and transforming it into a form that is HTTP compliant, which can be returned to a web browser via a user request (Mitchell, 2000). The diagram below indicates the architecture of the ASP and its significant components.
The script code used should be able to support the features that available in the scripting language. One significant aspect of the ASP engine is its capability to handle COM objects. COM objects are one of the built-in components of the ASP that are usually available in web services scripted with ASP. Other important components that are available in the ASP include the Request Objects and the Response Objects which are used for handling the input and output respectively for a given web page that has been scripted with ASP (Morneau & Batistick, 2000).
The Session Object is also an important component of the ASP that is used in the management of data that a user manipulates over the web browser in a given duration of time. The Application object is used in the management of a user’s session (Morneau & Batistick, 2000).
The Active Data Objects (ADO) does not form part of an inherent component of the ASP, it is a must that it is created and implemented in the web server through the use of the command line CreateObject(). Components development in ASP is a complex process because the components that are run in the IIS are prone to crashing (Mitchell, 2000). In addition, they can cause the web server to hang or completely fail on some cases. The complexity of component development is also experienced because during run time, they are almost impossible to debug.
The functioning of the ASP technology
The functioning of the ASP can be said to be primarily based on the server side scripting approach. This means that the web server loads, executes and returns the output with limited involved of the client except in cases whereby the script execution requires input from the user (Morneau & Batistick, 2000).
The execution of a server side script begins when a web browser invokes a request for an .asp file that is stored in the web server. It is the responsibility of the web server to call the ASP, which is duly responsible for the processing of the requested file in a top to bottom manner. This process is called HTML parsing. The scripts are not accessible to the users under any circumstances (Morneau & Batistick, 2000).
The creation of the ASP web applications varies according to the scripting language used. The ASP provides a framework for the creation of server side scripts that can be used in any scripting language and programming language that is COM compliant. Basically, an ASP file of any scripting language should have an extension of .asp. The three basic components of an ASP file include the Text, the HTML tags and the server side scripts (Francis, 1998).
A basic way creating an .asp file is to rename an.html file with an .asp file extension. It is important that the file should contain the ASP functionality in order for the web server to process the asp file and send the output to the client via a web browser. A virtual directory is required in order to save the .asp files on the web site. It is also important that the virtual directory should be script enabled and has the permission to execute scripts. HTML parsing is used in transforming the .asp files into the normal HTTP files in the client’s browser. Any text editor can be used in the creation of .asp files, provided they are saved with the required file extension.
The addition of the server script commands is also another significant step in the creation of ASP applications. In this context, the scripts are distinguished from ordinary HTML tags and Text by use of delimiters. When embedding scripts in HTML, the delimiter symbols used are < and >, which are used to enfold tags written in html. The ASP deploys <% and %> to nest the script commands (Shaw, 2003). Any scripting command can be placed anywhere within the enclosure of the HTML tags. An example of script command that can be used to develop a web service enclosed in HTML is shown below.
This web page was last viewed on <%=Now () %>
The Now () function is a VBScript command that returns the current date and time to the web based application or browser. Script commands that are nested in the delimiters are referred to as primary script commands. ASP delimiters can accommodate any statement or expression within them, provided they are valid in the primary scripting language that the developer is using (Mitchell, 2000). Procedures and operators can also be embedded within the script delimiters in order to enhance the interaction within the ASP web application that is being developed.
Security is an important aspect of any web based application and the implementation of security in an ASP web application is not an exception. There are various methods that the ASP technology uses to enhance security during the development of web services. One of the first approaches that the ASP uses in ensuring security is through the use of membership management accounts. The ASP.NET framework provides an avenue through which security information such as login names and their matching credentials can be stored and only retrieved once a user provides the necessary credentials needed for access (Shaw, 2003). This is achieved through the identification of users who log into a web site and storing the necessary information concerning their credentials.
The ASP technology is somewhat intelligent in the sense that it can associate particular users within specified role. This is a security strategy that attempts assign specific user accounts to performing specific tasks in the application. The ASP technology can also be used to limit the number of users who access a given web page and the embedded web based application. Access limitation in ASP can be realised in two basic forms: File authorization and the Uniform Resource Locator (URL) authorization (Mitchell, 2000).
ASP versions and their applications
There are three major releases of the ASP since it was first developed: the ASP version 1.0, ASP version 2.0, and ASP version 3.0. The ASP version 1.0 was distributed with Internet Information Services 3.0 during December 1996. This first version of the ASP was compatible with Windows NT option pack. The ASP version 1.0 had serious performance issues that caused server slowness, the web applications that were implemented under the ASP version 1.0 caused the web server to hang or sometimes cause complete failure during the cases of non-responsive scripts (Francis, 1998).
The ASP version 2.0 was implemented using Information Internet Service 4.0 during 1997. The second release of ASP served to provide a solution to the performance issues that were associated with the first release. The second release had six significant objects that were built: Application, a platform for request, a platform for Response, Server and the session. This release incorporated the concept of active scripting using COM, which provided functionality that allowed web services developed in ASP to access compiled libraries (Mitchell, 2000). An example is the DLLs.
The ASP version 3.0 was released during was released during November 2000. The third version was distributed with Information Internet Services 5.0 and served as an improvement to the previous version. In addition to the five objects available in ASP version 2.0, ASP version 3.0 had an additional object called ObjectContext and ASPError (Strahl, 2002). This means that the third release had additional error handling features that were more effective compared to the earlier releases of the ASP. The error handling object was an intrinsic object that was developed in the ASP version 3.0, meaning that there was no need to load external programs to handle errors in the server side (Morneau & Batistick, 2000).
In addition, the development of ASP version 3.0 reported reduced cases of non-responsive scripts and performance related issues on the server. The third release provided an avenue for the development of effective web applications. There were particular enhancements in the ASP version 3.0 that made it revolutionize the development of web based applications. One such enhancement was the Server Transfer, which was used to transfer the controls of an ASP web page to another page. This new enhance served to eliminate the slowness associated with the Response Redirect of the earlier releases of the ASP (Strahl, 2002).
Another significant enhancement under the ASP version 3.0 was the Server Execute, which was used to redirect the controls of ASP web page content to another ASP web page. The only difference is that the redirection takes place after the Completion of execution.
The latest release of the ASP has significant features that can make it easy to create interactive web services. Apart from the Flow control capabilities and error handling, there are other various approaches that are implemented in the ASP version 3.0 that facilitates the development of web applications. An example is the Script-less ASP, performance enhancing objects that are achieved through the use of components that can be installed in the ASP. XML integration is also another significant feature that was incorporated into the ASP version 3.0 (Shaw, 2003).
Strengths and limitations of the ASP technology
Any computing technology is susceptible to a number of strengths and weakness. The ASP technology is not an exception is such a context. The strengths and weakness of ASP are determined by the number of functions that the ASP supports.
The first basic strength of the ASP is the ability to add script commands on the server side, which consists of a sequence of instructions that are used issue scripting commands to the web server. This is achieved through the use of primary script commands that are embedded in the scripting language (Morneau & Batistick, 2000).
The second significant strength of the ASP is its ability to integrate HTML tags and script commands. This helps in determining how dynamic and interactive an application is. It also provides an avenue through which multiple procedures can be defines in a scripting language under the ASP. Script commands can be used output the HTML text to the browser. To reverse the process, the ASP has an in-built Response Object (Mitchell, 2000).
Another significant strength of the ASP is web developers can use it create scripts that are executable on a server irrespective of the scripting language. It is also worth noting that a single .asp file can contain a number of different scripting languages. This eliminates the need for the client web browser to support scripting since all the scripts are processed by the web server. The effectiveness of the ASP can be used to manipulate scripts that are running on the client side. Another significant strength of the ASP is that it can be integrated with HTML forms to make database access more efficient and secure through the use of database connections (Mitchell, 2000).
The ASP provides a platform for the development of transactional applications that are web based. This is one of the significant strengths of the ASP in the development of web applications. In addition the ASP provides a platform for the development of web based applications that are scalable, and the resources required can be manipulated in accordance with the client’s needs (Shaw, 2003).
There are also drawbacks associated with the use of ASP. One such significant weakness of the ASP is that the client has no control or the ability to manipulate the server-side scripting. This means in cases where the scripts become non-responsive or stops functioning, the client has no control and suffers the ineffectiveness associated with web server breakdown. Another significant weakness of the ASP is that it only functions effectively within the windows environment on the server side (Francis, 1998).
Conclusion
The ASP was one of the significant inventions that played a significant role revolutionizing the development of web based applications. Almost every website in the current internet requires an element of dynamism and interaction that is automated. It is in such scenarios that the use of ASP is of great significance. Therefore, ASP forms one of the most effective platforms for the development of web services.
References
Francis, B. (1998). Beginning Active server pages 2.0. New York: Wrox Press.
Mitchell, S. (2000). Designing Active Server pages. New York: O’Reilly Media, Inc.
Morneau, K., & Batistick, K. (2000). Active server pages. New York: Course Technology.
Shaw, J. (2003). Adding Member services in ASP. Technology, 5-40.
Strahl, R. (2002). Using VFP COM Objects with Active Server Pages. West Wind Technologies, 90-122.