Author: Geoff Crawford

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Title: Web Based Application Tiering Author: Geoff Crawford It s not often you get a chance to look back on a project, come to a new understanding of what you could have done better, and then go back

1 Title: Web Based Application Tiering Author: Geoff Crawford It s not often you get a chance to look back on a project, come to a new understanding of what you could have done better, and then go back and actually make the improvements. But such was the case while creating a WebSpeed application for a major client. We had done some training and worked through the code created by the WebSpeed Workshop Wizards. We felt kind of confident and took a small project that would build on an existing application, creating a web front end for quick queries about inventory levels. Having a strong software engineering background, I had been taught modularity and the interfaces between modules were key elements of software design. Eager to apply that conventional wisdom to our web programming, I began by sketching out a couple of web pages and the flow from one page to another. As part of good engineering practice, I encouraged definition of the inter-page parameters using the three methods possible - the URL, cookies, and hidden fields. As we began to actually program these, there were no major problems encountered and so we moved on. After what seemed like some reasonable success, we decided to create a small help desk system for internal usage. While designing these screens and looking at the page to page interaction, it dawned on me two interface styles evolved. One method was continuously submitting the same web page over and over again. This seemed natural enough for a browser type screen that would display 10 lines of information with next page and previous page buttons. Those Figure 1 A typical page generated by WebSpeed Workshop for updating the State Table. When this page is submitted, the exact same page is returned except for the Add button. This confuses the user and violates proper Web based tiering Innov8 Computer Solutions, LLC. 1

2 buttons would then call the same program over again, passing in parameters of where the query was positioned during the previous page, and what the next action would be. The program could then reopen the query, position to where the query had left before, then perform the requested next or previous function. WebSpeed Wizard generated code works this way. When we began to write Embedded Speed Script (ESS) pages from scratch, some programs still came out this way, but a second type of interface developed. Instead of calling the same program, a string of subsequent pages would be involved. Logically I decided that each page should inform the user what had happened, including any errors, and what the next steps could be for the user. A screen for the End User to enter a Trouble Ticket was developed using the second interface. The user would type their details and then click on the save button to call the next program. The resulting page would tell the user Congratulations, a new ticket with Number: has been created and give a choice of three buttons for navigation. One for going back to entering in another ticket, one for updating the ticket they just created, and another for going to a trouble ticket search screen. Conceptually, this has its advantages because it closely resembles a state diagram between web pages. Most of the application had been built when I began to get the feeling that I was missing something. My realization two methodologies had developed sparked questions such as: what were the advantages and disadvantages of each, what were the best times to employ each, and ultimately how should web based applications be designed. Inclinations came in bit by bit. The first clue occurred during the initial demo of the application to an end user. After updating a Trouble Ticket, the user pressed the save button and was presented with the same screen allowing for modification of the record, only with the words Record Updated at the top. This program had been developed with the wizards so it was a Type 1 screen. After some thought, it dawned on me that the two job functions of saving the data and offering it for modification are vitally different. So different that combining the two violated encapsulation of the program s job function. Thinking about encapsulation and how that leads to violating object tiering lead me to the ultimate revelation web based applications have a different tier structure than traditional Client/Server. Why Tier So what is the big deal about tiering, encapsulation and the other pieces of modern thought on object orientation? Software engineering has taught us for years that modularization allows for easy maintenance and modification of complex source code. As software began to be built with interchangeable, discrete objects, it became even more critical to modularize each object to the level where it would be completely selfsustained, encapsulating all its specific job functions and the interfaces needed (input/output parameters, etc.). Without properly encapsulation, the components we build are no longer reusable and we lose the purpose behind a component based software model Innov8 Computer Solutions, LLC. 2

3 Encapsulation needs to happen not only on a small inter-component level, but also at a higher, inter-module level. Today s computing architectures no longer are confined to single computers. With the popularity of Client/Server we now need to create components that are distributable across the application s possible places of execution. In order to do that, a tier structure of component groups that form interdependencies needs to be developed and adhered to. Without it, a single component that mixes tiers requires both modules to be co-resident on a single execution point and eliminates the possibility of n-tier distribution. By following proper tiering in a web based architecture, we hope to gain these objected oriented benefits of modularity, interoperability, and distributability. Tiering On A Web Basis So how do we apply these principles to the Web, particularly using WebSpeed? HTML Mapped pages, Embedded SpeedScript, and CGI Wrappers all have the same general capabilities of reading the input stream for values passed in, then output a resulting web page. The trick is not to use both for job functions that depend on each other. In our example above of the Trouble Ticket Entry screen, there are in fact two distinct functions. One is to output an HTML entry screen, populated with the current database values in an update mode if need be. The other is to take the modified values presented to the user, and store them back in the database. By combining these two jobs together, we can no longer distribute, or reuse the same code because they are irrevocably tied together. We cannot for example, use a Microsoft Active Server Page (ASP) to pass information to be stored in the database. However, if the two pages were distinct, with a defined interface, such interoperability would be possible. In addition, separating the web pages also allows us to run each one on a different web server. Tiering means the separation of objects specific job functions. In the case of Web applications it dawned on me that generating the HTML for data input is one of the tiers, and accepting the inputs to go to the database is another. My terminology is UI Generator Pages and Data Acceptor Pages. It is not that Data Acceptors do not generate UI or that UI Generators cannot accept data as input. The idea is that each performs specific functions surrounding its job. In the example of the End User screen, the page the user types in their problem is the UI Generator. It creates an HTML screen with all the pieces of information needed to create a new Trouble Ticket. The page will have to do some acceptance of data input, such as the ROWID of the user record in the database, but only in relation to it s job of showing the user their phone number and contact method (i.e. information used in the UI). This UI Generator then passes on the data fields to the Data Acceptor (DA). Because we have properly tiered our application, that Data Acceptor can be written in some completely different language, and can be on a completely different web server. DA s do present a web page back to the user, which might be considered a form of UI. However, the page returned has the purpose of showing confirmation of Innov8 Computer Solutions, LLC. 3

4 the data entry and gives no opportunity to view or manipulate data. The pages DA s create generally offer navigation, another job function needing consideration. As it turns out, navigation buttons and links are associated with neither allowing the user opportunities to change data, nor the programs that actually save the data to the database. Navigational features are by their very definition encapsulated as well as distributable because the button or link contains its own URL. They form a sort of non-intrusive third tier that does not interfere with the purposes of the other two and additionally preserve their own object orientation. After this application was built, it was destined to be turned into a commercial product through a deal with the client. That gave the unusual opportunity of going back and reworking the page architecture to conform to the new tier process. The distributability and interoperability of the application became such that two sets of entirely different looking screens were developed. One was a more traditional, almost text looking interface, and the other with dynamic buttons, tables and a measure JavaScript thrown in. The user may choose to use the fancier interface pages for their menus, but the traditional ones for data entry. Although outside the scope of this application, there is no reason some pages could not be written in another environment such as ASP or Cold Fusion. This mix and match capability was only possible through the proper tiering of the application. Figure 2 A sample Embedded SpeedScript program for Data Acceptor. Notice how the program has a set structure of sections built from a standard template for Data Acceptors. <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> <html> <head> <meta name="wsoptions" content="no-output"> <title>request Received</title> </head> <script language="speedscript"> /* Define Section */ DEFINE VARIABLE Nme AS CHARACTER. DEFINE VARIABLE Abrv AS CHARACTER. DEFINE VARIABLE Terr AS CHARACTER. /* Assign Section */ ASSIGN Nme = get-field( StateNme ) Abrv = get-field( StateAbrv ) Terr = get-field( StateTerr ). /* Processing Section */ FIND State-File WHERE State-File.StateName = Nme NO-LOCK NO-ERROR. IF NOT AVAILABLE State-File THEN DO: CREATE State-File. ASSIGN State-File.StateName = Nme END. /* New State */ ASSIGN State-File.Abbrev = Abrv State-File.Territory = Terr. </script> <body><hr>  <center><font size= +1 >Thank You!<br><br> <font size= 0 >State `Nme` Updated.<br><br>  <a href= index.html >Return To Main Menu</a> <a href= statelist.html >Modify Another State</a> </body> </html> Innov8 Computer Solutions, LLC. 4

After the user enters their data, the page is simply submitted to the Data Acceptor for processing. Figure 4 The resulting Data Acceptor.

5 Figure 3 A UI Generator from a Help Desk application. The user is presented with all of the approriate data items, including drop down lists of Priorites, Operating Systems, Locations and other data fields. After the user enters their data, the page is simply submitted to the Data Acceptor for processing. Figure 4 The resulting Data Acceptor. The SpeedScript program creates the Help Desk Request associated with the data from the UI Generator and then produces the following page. The user is informed of the action performed, and is given a choice of four navigation options. Phone: (973) Fax (973) info@innov8cs.com Web: Innov8 Computer Solutions, LLC. 5

Dynamic File Maintenance using WebSpeed

Dynamic File Maintenance using WebSpeed A FreeFramework Approach Hansdip Singh Bindra Phone: (973) 361-4224 Fax (973) 537-6946 E-Mail: info@innov8cs.com Web: www.innov8cs.com 1999-2005. Innov8 Computer