Detect Windows Version with VB Script
May 13, 2008
This post as most of my other posts is dedicated to windows developers 
Many times you are in the scenario where you want to detect the Operating System Version on the client machine. I had this when i developed a windows application and wanted to deploy it on different platforms including Windows 2000 XP or whatever NT hahaha this works for all .
So i wanna share just in case anyone has the same scenario :
I have shown the message boxes for debug purposes . Feel free to use or modify it : D happy development
‘ Muhammad Asad Siddiqi
‘ This can be run by executing cscript and passing the file name in the command prompt
‘ Purpose = “To detect the current version of the windows and execute files for XP or NT
‘ This would be made a part of Fail Safe to decide on PULIST or TaskList commands
‘ Variables used in the script
DIM szTempFileName
DIM szCommand
DIM wShell , FileObject
DIM nErrorCode
DIM remoteAppFile
DIM szLine
DIM ResultNT,ResultXP1,ResultXP2
‘ Create the temporary file as C:\TEMP\WindowsVersion_CT.txt
szTempFileName=”C:\TEMP\WindowsVersion_CT.txt”
‘ Initialize the Windows Scripting Shell instance
Set WShell = CreateObject(“Wscript.Shell”)
‘ Initialize the Windows Scripting File instance
Set FileObject = Wscript.CreateObject(“Scripting.FileSystemObject”)
‘ DEBUG # 1 TODO – Remove This
MsgBox (“Starting”)
‘ Check if the file already exists delete it
if FileObject.FileExists(szTempFileName) then
FileObject.DeleteFile(szTempFileName)
End if
‘ DEBUG # 1 TODO – Remove This
MsgBox (“File System Checked”)
MsgBox (szTempFileName)
‘ Execute the ver command to get the windows info detail
szCommand = “%comspec% /c ver >”& szTempFileName
‘ DEBUG # 1 TODO – Remove This
MsgBox (szCommand)
‘ Execute the command and get the error code
nErrorCode = wShell.Run (szCommand , 0, TRUE)
‘ Check if the command is ran successfully
if nErrorCode = 0 then
‘Get a handle to the file where result of ver command is written
Set remoteAppFile = FileObject.OpenTextFile( szTempFileName , 1 , TRUE )
‘ Loop through the file till end of file character is not encountered
do while not remoteAppFile.AtEndOfStream
‘ Read the line from the file
szLine = remoteAppFile.ReadLine
‘ If the line we have read is not an empty line then check
if szLine <> “” then
ResultNT = InStr(szLine, “4.0″)
ResultXP1 = InStr(szLine, “XP”)
ResultXP2 = InStr(szLine, “5.1″)
if ( ResultNT <> 0) then
MsgBox(“Win_NT”)
elseif (ResultXP1 <> 0) then
MsgBox(“Win_XP”)
elseif (ResultXp2 <> 0) then
MsgBox(“Win_XP”)
else
MsgBox(“Unknown Windows”)
end if
End If
loop
remoteAppFile.Close()
if FileObject.FileExists(szTempFileName) then
FileObject.DeleteFile(szTempFileName)
End if
End if
Designing Web services with REST
March 27, 2008
REST is an acronym for Representational State Transfer. REST can be described as an architectural style (not a standard) of networked systems. This architecture is vastly becoming popular with Web services. The underlying protocol which is used with web services is http and the distributed systems are connected through the web (internet). REST is an alternative architectural style to SOAP (Simple Object Access Protocol) which instantly gained popularity with the advent of web services and is the widely used standard for web services data transfer. In this essay I would highlight on the working of REST, the implementation style, characteristics, and principles and compare the architecture with SOAP and try to conclude which one might be better and under what circumstances. In the end I would explain how to use REST with web services by designing a dummy web service which follows the REST architectural style.
So what does Representational State Transfer mean?
As we all know Internet is a collection of various resources. All the resources on the internet (including the web services with a published wsdl) can be accessed through a uniform resource locator (URL) e.g. http://www.mywebsite.com/mywebservice.With Web 2.0 in action static websites are loosing visitor’s interest and we see more and more dynamic web applications like forums, interactive blogs, websites which are regularly updated by users. Example of these applications are wikipedia where the user can moderate the content instantly , youtube where users can update their videos and they immediately become available to potentially everywhere the web application could be accessed with a browser and EBAY where there is real time bidding by the users of the web applications. With REST as the underlying protocol is Hyper Text Transfer Protocol (HTTP) the application changes or transfers its state after each http request / response for each requested resource.
“So REST can be considered as an architectural style where a web application changes its state constantly and it is named as Representational State Transfer”.
Roy fielding (A researcher of this architectural style, defined the key characteristics, motivations, benefits and the circumstances where its implementation might be beneficial) explains REST as:
“Representational State Transfer is intended to evoke an image of how a well-designed Web application behaves: a network of web pages (a virtual state-machine), where the user progresses through an application by selecting links (state transitions), resulting in the next page (representing the next state of the application) being transferred to the user and rendered for their use.”
The motivation for REST was to capture the characteristics of the Web which made the Web successful. Subsequently these characteristics are being used to guide the evolution of the Web.In the beginning of the essay I emphasized on REST being an architectural style and not a standard. REST is a way in which web services can be configured to deliver data streams or we can say that client accesses a resource on the World Wide Web and is certainly not a standard like HTTP or XML. The concept is much similar to what Web 2.0 is, you want see W3C putting out a specification on the working details on REST. Same is true for the vendors of software development technology, the software giants like Microsoft, sun and other platforms manufacturers won’t come out with a REST development toolkit simply because it’s an architectural style. By architectural style I mean a way of implementing things or we can say that defining a framework using the existing technology and using it in a way which is more efficient and effective for us. Although REST is itself not an industry standard but as it works with the Web and the distributed world of internet it works in parallel with many industry renowned standards. These include HTTP, XML, HTML, URLs and various file formats like gif, jpeg, text/xml, text/html and other MIME types. Many of the services especially the web services that we use as out day to day routine for our usage and software development services are based on REST and we are even not aware that we are using it. This is because REST does not work with minor implementation details it has more to do with the overall integration of the components that make a web application or a web service work.
So what are some of the key characteristics of REST?
As we know that the model that http follows a Client Server paradigm (as it works on the internet) where the client is the consumer or requests a resource identified by a URL and located on the World Wide Web and the server is a web server which has the required resource and delivers it using HTTP. The Client Server paradigm is further classified into a pull or push based implementation Style. REST is essentially a pull-based implementation style of http where the consumer (consuming services, applications e.g. browser) or client pulls various representations (resources). Another Key characteristic that rest follows and is due to the http being the underlying protocol is it’s stateless. As we know that http is a stateless protocol so each request from client to the server in this http pull-based implementation style should contain all the information which is necessary for the server to understand the request. In other words the client cannot take advantage of any information that is stored in the server’s context and has to send the client’s info with every representation transfer. An optimization and a key characteristic that REST utilizes to overcome performance limitations and overheads is CACHING. When the web server responds to any of its clients with the requested resource the responses should have the ability to be marked as either cacheable or non-cacheable depending on the capability of client which might be an application or a service. So if the client if Caching enabled the performance can be optimized as the implementation architecture supports caching. What it means essentially is if the same resource is requested by the client again and again or for instance the same parameter or argument is passed to a method exposed by a web service the client should know what the service will return and it should directly get the desired result without going through the whole request/response process. Another key characteristic of REST is all REST implementation should follow a uniform interface .This means that all the resources located on the web server can be accessed by using a generic interface such as HTTP Get, Post, Put or delete. In a REST based implementation, each resource that is requested from a web server can be identified with a unique URL. This is pretty much how internet works, the critical components here are the Client and Server Applications, HTTP as the request/ response based protocol, and the Domain Name System (DNS) which resolves the host names to IP Addresses to exactly know where the requested resources are physically located. So it is essential to use named resources while implementing REST. Another key characteristic of REST is interconnected resource representations. This essentially means that the representations of the resources are interconnected using URLs, thereby enabling a client to progress from one state to another. REST uses Layered components which imply that intermediaries, such as proxy servers, cache servers, gateways, etc, can be inserted between clients and resources to support performance, security, or in other words using intermediary devices between the client and the server does not restrict the client from accessing the server. Etc Designing web services using REST:
What are some of the key design principles that we have to keep in mind while designing web services that makes use of REST? Primarily all the conceptual entities that the designers or developers wish to expose as services need to be identified. The design principle is not only limited to REST but it’s a general rule of thumb for good web service design. As we know, one of the characteristics of REST is using named resources. Recall that resources are named as URLs .REST uses a particular naming convention to access resources on the web server. REST proposes to use nouns as resource name instead of verbs.
E.g. URL such as http://www.bookstore.com/books/getBook?id=11234 should not be used instead the resource should be named as http://www.bookstore.com/books/11234 REST follows the phenomenon of categorization of resources. The resources should be categorized in terms of whether they can only be accessed and not changed by the client. Such resources are called Read Only Resources. With Read only resources clients can just receive a representation of the resource. In addition to this the clients can add new resources or modify existing ones. REST suggests categorizing the resources based on resource types. If they are read only resources which the client can access but not modify, only HTTP Get should be specified as an access method whereas if the clients can update the resources then HTTP POST, PUT, and/or DELETE can be used. In this context all resources accessible via HTTP GET should not have any side effects. That is, the resource should just return a representation of the resource. Invoking/calling or requesting the resource should not result in modifying the resource in any way. As from the above description it is evident that REST (Representational State Transfer) follows a state based implementation, it supports how we can drill down further into the application. REST supports navigation by supporting navigational links so the state of the request changes and recorded. For designing a REST style web service some performance optimizations are provided as the design guidelines. REST proposes not to present the whole data in one single response simultaneously to the user (client). Instead present a portion of the data with the ability to drill down information by providing navigational links so the user can drill down by again requesting a resource identified the navigational link and thus the state of the client application changes. If a web service is to be designed that uses REST as the architectural model, the format of the response data has to be defined using a standardized schema such as the Data Type Definition (DTD) or W3c schema or Schematron e.t.c For those services that require a POST or PUT to it, also provide a schema to specify the format of the response. The SOAP and REST comparison: Having discussed the working of REST, characteristics and principles of a typical application that follows a REST based architecture and knowing that it is a design alternative to SOAP (Simple Object Access Protocol) the question that comes to our mind is when to use REST and when to use SOAP , what is the key factor that answers this question ? What are the benefits of REST over SOAP and vice versa? Although there are plenty of overheads which can be immediately noticed with implementing SOAP, writing a wrapper class that puts a SOAP envelope on every request response that goes to and from the web service on the client side and configuring the service itself to parse those request may sound like a lot of work. But primarily we now have tools to do it; I have worked with Microsoft Visual Studio where if a wsdl file hosted on the internet is given as an input all the wrappers required for the web service and initializing SOAP are generated automatically, same is true for many DELPHI environments. The advantage of using SOAP is “sending complex data structures to the web service”. Development tools like Visual Studio or Delphi can read the WSDL from the web service and that gives you the "INTELLISENSE" auto completion functionality that can save a lot of coding time. The drawback with SOAP is that there is more overhead in the construction of the method request and with the parsing of the request on the web service end. When you have a web service that is serving thousands of requests a minute or second, that overheard may not be needed. This is in contrast with REST where simple HTTP Get and PUT commands are used to interact with the web service. You compose a URL for your web method request and the service sends back a response. The response is usually in XML, but that is dependant on the functionality of the web service. For web services that have relatively simple data types, using REST can provide the functionality that is needed. You also get the advantage of testing individual method requests from a browser as the method request is basic URL. Another big advantage of using REST over SOAP is by sticking to simple semantics (especially if you limit yourself to GET as much as possible); it scales much better as it can take advantage of all levels of caching between you and the server. REST takes advantage of the existing scaling mechanisms the internet has grown on top of HTTP - something SOAP cannot do. The complex data types can still be used with REST by including them as payloads - you just have to manage interpreting it yourself instead of relying on a rich library layer to make it feel like some native type in your program. So if we compare the contrasting architectural styles, REST is the way to go if you are looking for better performance and the web service consists of simple data types where as SOAP would be better if the client application has to be developed fairly quickly and Complex data structures are to be used. A REST example – An Online Library Catalogue exposing library data as a service ( A self created dummy service to demonstrate REST) : Here I would describe the whole process of how REST works and some of the common practices that are followed by developing a simple Library Catalogue Service which would define a couple methods of displaying a list of books and listing a particular book’s details. The functionality that is exposed by the service is: Generating a list of books Generating details of a particular book
Generating a list of books:
The web service presents a URL to a “Book listing” resource. For example, a client would use this URL to get the parts list:
The client does not know anything about how the listing is generated by the service. All the client knows is that if he/she submits the above URL then a document containing the list of books is returned. Since the implementation is transparent to clients, the Book’s catalogue is free to modify the underlying implementation of this resource without impacting clients. This follows two major principles or concepts of Software Design, loose coupling and encapsulation.Here’s the document that the client receives whenever the above URL is accessed:
http://www.books-online.com/books/00001
Here’s the document that the client receives:
ADO.Net Explained step by Step
March 14, 2008
In this tutorial I would be talking about integrating databases in your .Net Applications specifically C# applications. ADO.Net is a .Net framework’s library which is essentially the same for ASP.Net for web development and other desktop applications using C#.Net or VB.Net. In my experience the database that was used most frequently was Ms-SQL Server, off course because both are Microsoft products. .Net seems to integrate with SQL Server very easily and gives better performance. (ADO.Net provides a Namespace specifically for SQL Server which might result in better performance with SQL Server. It is prescribed to use System.Data.SqlClient when using SQL Server as your back end instead of System.Data.OLEDB) Having said that .Net can connect to all the major databases systems. The ones I have worked with include Oracle, Sybase SQL Anywhere, MySQL and MS-Access. For the sake of discussion I would be connecting to SQL Server Database here to show how to connect to databases using ADO.Net and do the routine operations.In many books I have seen hard coding of ADO.Net objects and configuring the data sources and some properties of ADO.Net objects which pisses me off. Simply ask yourself the question How are you going to deploy such software? Is it easy to replicate your development environment on the Target client machine? NO !! Not at all!! It’s a nightmare. So setting all the properties in code and all the configurations in a configuration file is the mostly used conventional way of doing things.
Prerequisites for this are some knowledge of C# and I would assume that you have a DBMS available that you wish to use for your practice or running sample code against.
Connecting to Database:
The easiest way to ensure database connection is through a UDL (universal data link) file. Simply create a new text file on your desktop, open it and from the file menu choose the “Save As” Option. In the “Save As” dialogue for file type select “All files” and for file name specify “abc.udl” and save the file. When you close the file you should have a new file called abc.udl. UDL FILES are a Microsoft proprietary file format that is used to configure data sources.
Simply enter your Database info and select the “Test Connection” Button. Once you see the message box that says “Test Connection Succeeded” close the dialogue by clicking “OK” and close the “Data Link File”. Open the file with notepad or any text editor and the third line in the file is the connection string.
An Alternative approach to connection:
If the above mentioned process sounded too complicated which it is not the following connection strings can be used:
For SQL Server use:
Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
For MS-Access use:
Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\myFolder\myAccess2007file.accdb;Persist Security Info=False;
For Oracle use:
Provider=msdaora;Data Source=MyOracleDB;User Id=myUsername;Password=myPassword;
For MySQL use
Provider=MySQLProv;Data Source=mydb;User Id=myUsername;Password=myPassword;
The first step to talk to databases is to include a reference to ADO.Net library in your code. You don’t need to do it explicitly. Simply use the following statements in the beginning of your code.
using System.Data;
using System.Data.OleDb;
Once you have decided what database you want to connect and what connection string you have to use then your C# code starts. I would make a small method that returns an instance of System.Data.Oledb.OLEDBConnection if a successful connection is established else returns a null.
/// <summary>/// Open the Database Connection/// There should be an entry for “Database” in the app.config
/// </summary>///
<returns></returns>
public System.Data.OleDb.OleDbConnection OpenConnection()
{
OleDbConnection conn;
string connectionString = ConfigurationSettings.AppSettings["Database"];
try
{
conn = new OleDbConnection(connectionString);
conn.Open();
return conn;
}
catch (Exception ex)
{
return null;
}
}
Executing an SQL Statement:Whenever you are designing or developing a database centric application, you have to perform database operations ( Select , Insert , Delete , Update) from various places within your application. Here we would discuss about the most common scenarios like there is a dropdown list from where the user selects one or more items. How to populate the Combo box? . We want to show the user search results in a datagrid or a datagridView in a windows forms or a web form. ? We want to add new records in the database How to do it ? Below you will find answers to all such questions. For the sake of discussion let us consider we have a table in our database called Student and the columns/attributes of the table are Name,ID,Date_Of_Birth,Address,Email , Phone and SSN. I will show you how to manipulate the table from our application using ADO objects and give you some example code to play around.
Executing a Select Statement for a dropdown list:
Suppose you have a form where you want to update the students record.You have a dropdown where you will display all the SSN of the existing student. When the user selects the SSN the form gets filled automatically by selected students information. The user can then make changes and click a button and the changes are saved to the database.
OK, the easiest way to load a combo box or a drop down list is by using an OLEDBDataReader object. The method with the code is shown below:
public OleDbDataReader ExecuteDataReader(string query)
{
try
{
OleDbDataReader reader;
OleDbConnection conn = OpenConnection();
OleDbCommand cmd = new OleDbCommand(query, conn);
reader = cmd.ExecuteReader();
return reader;
}
catch (Exception ex)
{
return null;
}
}
You can call the method , get the data reader and then loop through all the items this would be something like on the form_load event of your form: // This is how you call the ExecuteDataReader Method
OleDbDataReader dr;
dr = ExecuteDataReader(“Select SSN from student”);
cmbStudents.Items.Clear();
while (dr.Read())
{
comboBox1.Items.Add(dr[0].ToString().ToString());
}
Executing a Select Statement to show in a datagrid or DataGridView:
The process of showing some rows of the database on a datagrid or a datagridview is essentially the same process with slightly different objects and the ways you use them.I am really pretty much against hardcoding stuff in the datagrid , the conventions you find in your first C# Book probably.I learned the fact, the hard way and believe me its no good at all. Probably good to make u understand what are the properties and what objects are closely connected or work together in the architecture.Always try to set the properties from your code instead of the designer view when it comes to ADO.Net objects like DataSet,DataReader,DataAdapter,DataGrid,Connection,Command e.t.c. Whenever you want to use Datagrids or DataGridView , the essential property is the “datasource”.This requires an instance of the dataset which has the results of the query passed in. The essential ADO.Net objects here are DataSet,DataAdapter and the DataGridView itself and that is it !!Following is the example of how to use:
/// <summary>/// Given a query executes a dataset and returns the dataset
/// Ideal when to be shown on a Grid View for searching or display
/// </summary>
/// <param name=”query”>The Select query that returns a dataset when executed</param>
/// <returns></returns>
public DataSet ExecuteDataSet(string query)
{
DataSet ds = new DataSet();
try
{
OleDbConnection conn = OpenConnection();
OleDbDataAdapter da = new OleDbDataAdapter(query, conn);
da.Fill(ds);
conn.Close();
return ds;
}
catch (Exception ex)
{
return null;
}
}
This is the calling code from where this method would be called:
DataSet ds = ExecuteDataSet(“Select * from Student”);
dataGridView1.DataSource = ds.Tables[0];
Note: You would also have to use dataGridView1.DataBind() if you are programming in ASP.Net
Executing an SQL statement that updates a table:
Here we are not selecting any rows from the database rather we want to run an insert , delete or update sql statement so we don’t want anything back from the database.So the OLEDBCommand instance is treated in a slightly different way. Below is a sample method which might be used to execute and update a database table:
/// <summary>
/// executes a given insert query and returns true if query is executed ok/// </summary>
/// <param name=”query”>The insert query which does not return any dataset</param>
/// <returns></returns>
public bool ExecuteInsertUpdateQuery(string query)
{
bool toReturn = false;
try
{
OleDbConnection conn = OpenConnection();
OleDbCommand cmd = new OleDbCommand(query, conn);
cmd.ExecuteNonQuery();
toReturn = true;
conn.Close();
return toReturn;
}
catch (OleDbException dx)
{
throw dx;
}
catch (Exception ex)
{
return false;
}
}
This method can be used as: string insertQuery = “insert into student values(‘1’,’2’,’3’);
bool status = ExecuteInsertUpdateQuery(insertQuery); In a similar way delete and update queries can be passed in and the method would return a true or a false indicating whether the statement was executed properly or not. So this was a brief brief introduction and a short tutorial, I would say “ADO.Net Crash Course” and I think there is much more to ADO than what I showed. Keeping in mind these are the essentials which you should know if you want to enter the database applications world with Microsoft.Net. If you make any additions to this article or simply provide feedback so I can make the required changes, or you want free consultation with your design, leave your comments as feedback.All your feedback is warmly welcomed and I would try my best to address your issues.
Aankhon mein teri Guitar chords
March 13, 2008
This is an indian movie song from the movie called Om Shanti Om . I haven’t seen the movie but I listened to this song and thought it was really impressive . I experimented a bit with my acoustic and came up with the chords which are I guess pretty much close . I play the barre chords in the E maj shape and the chords sound very much close to the real thing. Here are the tabulature for the chords just in case
A = 577655
F = 133211
F#m = 244022
G = 355433
Bm = 799077
E = 022100 (Open)
A A
Aankhon mein teri ajab si ajab si adaain hain
F G A
dil ko bana dein ju patang saansein teri ye hawain hain
A F#m F A
Tere Saath Saath Aisa , koi noor aaya hai
A F#m F A
Chand teri roshni ka , halka sa ek saaya hai
A Bm E A
Tujhay dekh k dil ka hua ju hashr asar ye hua
Bm E
ab in mein hi doob k ho jaon paar yehi hai dua
A A
Aankhon mein teri ajab si ajab si adaain hain
F G A
dil ko bana dein ju patang saansein teri ye hawain hain
A F#m F A
Ayee aisi raat hai ju buhat khush naseeb hai
A F#m F A
chahay jissay duur se duniya wo mere kareeb hai
Bm E A
Kitna kuch kehna hai phir bhi hai dil mein sawal wohi
Bm E
sapnoon mein ju roz kaha hai wo phir se kahoon ya nahi
A A
Aankhon mein teri ajab si ajab si adaain hain
F G A
dil ko bana dein ju patang saansein teri ye hawain hain
If you find any corrections , irregularities or suggestions do make sure to correct me by leaving a comment.Recording coming up soon 
stay tuned
Concept of Services Oriented Architecture
March 7, 2008
There are many different styles of applications that are written today. But lately we have seen a paradigm shift where the concept of “Software as a Service” is really been taken seriously. If you are an IT professional chances are 9 times out of 10 you must have heard of the term “Services Oriented Architecture”. What the heck? And you are like “Yeah, I know what that is and you go on … You make an application that consumes a web service!! Bingo!! ” No that’s not what SOA means’s is a new software development model or “An architectural style” where the business layer instead of integrated in the code is rather orchestrated :S . Confused already?? What I have realized over a period of time in the Software Market, whenever a new technology comes don’t jump into that technology and just know the couple POWER Words to horrify your bosses. I bet you 10 to 1 that Mr. John Doe or whatever!! Standing by the coffee machine and boosting about that “New technology” knows little about it.The key idea is to write software as a service ( It may be a web service or a windows service , a service within the enterprise accessible to you from your browser or a service that is published on the internet with a valid WSDL).If you notice the companies that have made it really big during the past year e.g. Google , Amazon and EBay I think the primary reason of their success lies with adopting the new software development paradigms and quickly able to deliver business rules with their service orientation.
So ok!! You want to know what exactly a Services oriented Architecture is. It’s a new software development paradigm which is suitable for applications with distributed processing capabilities .How it helps business?
Information technology is the backbone of nearly all major businesses. Nearly all major businesses today are Information technology driven. Any change in the business rules or business process (ways in which business is conducted) implies a change in the legacy system infrastructure. This change is sometimes difficult to implement as business logic or business rules are implemented as software code. The legacy systems lack the interfaces and are not designed to integrate / interpolate with newer systems, thus the company looses profitable business and a huge factor is the extent to which the legacy systems can be made scalable. We need a new paradigm of Agile Software development where we need to extract the business logic from the actual implementation and expose the data to other applications for quick integration. The idea is to design software architecture around a set of services which are loosely coupled, scalable, reusable and easily integrated. The architecture is called “Services Oriented Architecture” where software can be implemented as a set of loosely coupled and highly cohesive services that may be used by a number of internal / external applications.However, with its advantages there are upfront development costs (time and money) associated with changing the architecture of the software infrastructure and it depends on the nature of the business, the role of IT in the business and the different costs that are required to change the legacy systems whether the company want to adopt the new applications paradigm or not. With that said, it does provide lots of incentives once implemented properly including higher integration options, existence of business process as configurations, higher reusability, a higher degree of compliance with standards , increased cohesion within the sub system and decreased dependencies between subsystems Common misunderstandings:Certain level of misinterpretations and misconceptions about Service Oriented Architecture prevail .The primary misconception of this software architecture building methodology is due to a key technology the Web services. The service oriented architecture and the applications that follow SOA are often confused with just the Web services. Some of the common misconceptions are listed below:
Any application that uses Web services follows a Service Oriented Architecture.
An application that uses a Web service might follow a Service Oriented Architecture or it might not. It depends on the application’s own design, architecture and design considerations that determine its architecture.
SOA is same a re – branding Web services:Many people think that Services Oriented Architecture is nothing more than a marketing term which might be interchanged with Web services. The important concept they are missing over here is SOA is another Software Architecture that results in the functionality being distributed to many independent Services to better process Business processes.
Adopting a Services Oriented Architecture Ensures everything can interoperate:It is not necessary that any application that is developed as per the SOA artifacts would be able to interoperate or integrate necessarily with any other component / application or legacy systems. However SOA gives a high emphasis to increase the degree to interoperability by standardizing the Services produced using SOA.
If you can use a web service with your application you can easily develop applications based on SOA. SOA is the same as distributed computing with Web services. Pitfalls: If there were no potential hazards, problems and everything was ideal with implementing SOA perhaps all the enterprise software today would have been based on Services Oriented Architecture. It depends on the type of functionality, nature of components, exposed interfaces, degree of reusability and working of an application that determines it architecture. Some of the common pitfalls are mentioned below:
Designing and implementing an application like traditional distributed architectures:SOA is a relatively newer agile application development paradigm. Many of the new Services that implement SOA are designed just like a legacy application that followed a distributed architecture. This would involve Remote Procedure Calls, non standardized definition of services and an improper definition of the function boundary resulting in an increased degree of dependency and lowering the functionality contained in the Service.
Not making XML the foundation of application architecture:This also has something to do partly with standardization. All applications that follow SOA should conform to certain standards, the foundation of which is XML.Contemporary SOA cannot be achieved if the internal and external interfaces of the Service don’t use XML as a basis. e.g. A key enabling technology in the Services Oriented Architecture are the Web services. Web services are described using a WSDL (Web Services Description Language) which is XML based. Other than that the BPEL (Business Process Execution Language) and some other key components are also XML based.
Ignoring the Performance Requirements of a Service:Usually due to the communications overhead performance of applications or Services following contemporary SOA can be below the required level of performance. The message processing time for the service should be reduced by optimizing the code , reducing the number of request / response and it should be made sure that the Service meets the required response times and performance criteria. This can be done by extensive testing (Stress testing) for various input / output conditions. Not making the services secure:
SOA is most likely to be used as architecture for distributed applications. SSL (Secure Socket Layers) is not the security consideration here. The application designers should also consider the WS-Extensions and security frameworks provided by other vendors in order to provide a standardized software design that follows SOA principles.
Now you would ask hey hey hey!! Wait a second: S!! How BPEL, ESB, grid computing and the Business Intelligence do fits in? What the heck are these J I would be happy to explain if you have that in mind.For now just like John Doe who is standing by the coke machine hehehehe understands that BPEL is the Business Process Execution Language, ESB is the Enterprise Service bus and Grid Computing hmmm has many concepts for virtualization? Technically speaking these all are layers of the Architecture we discussed about called SOA and how these are written , mainly in XML yes business rules with xml is BPEL. ESB is where the services are available on one on many services. It can be taken as the medium where the services reside on the www. If you have any questions / suggestions / queries / ideas in your mind do post your comments. Thanks Note: I have taken the concepts of these pitfalls and disadvantages from a book on Services Oriented Architecture(Concept Technology and Design) by Thomas Erl
Object Oriented Design – A Class Diagram Walkthrough
February 21, 2008
Making a Class Diagram with UML Notation – Explained Step by Step:
Note: Your feedback , issues are warmly welcomed and I would be happy to assist you with any problem you might be having .Class diagrams are often used in object oriented analysis and design to show the various identified objects , their types (classes) , their data and operations and how the relate , or communicate with other objects or classes. Here are some of the standard UML conventions and a sample class diagram to get you started:
Identify the classes in the problem domain:
This is the first and most important step for creating the class diagram. What classes should you include and how to identify them given a problem statement or a scenario? The solution is simple and some time should be spent with the client / system engineers /your teacher in case you are making an academic project or any concerned authority having the required business knowledge.The first step however is creating a problem statement or establishing a set of requirements that the software should fulfill. E.g. you need to create a small library management system. What are some of the requirements for the system? Let’s try to make a problem statement or the scenario for your design. For the sake of simplicity considers the following simple problem Statement. “The library management system would be used by the librarian to keep track of books, library members and the borrowing activity. Not all books can be borrowed by the members. Some books may only be available to review in the library; all such books are termed as Reference books. There are 2 types of library members students and college faculty members. Faculty members can also check out research papers and magazines where as students can only checkout books. The system need to send alerts whenever a book that has to be returned within a specific date is not returned. An email is sent to the librarian and the borrower. The system maintains a catalogue having a description of each book that is available in the library”
Ways to identify Classes:
Do the Noun Analysis: Go through the problem statement again and again and try to figure out all the nouns that you come across. In our case some strong contenders for the classes of the library management system would be: Librarian,Book,Member,Catalogue,Student_Member,Faculty_Member,Reference_Book,Issueable_Book,Alert
Perhaps there might be some nouns that I skipped but why?? I did that intentionally because of either of the two reasons. Either there is no data associated with them. They have no role to play in the system i.e. they don’t have any functions or actions associated with them. So by this we mean that “In order for a noun to be an object or a class it should have some attributes or member data and some actions or member functions.
Resolving the relationships between classes:
Object oriented analysis and design is all about relationships between objects. Look for a certain type of relationships. These include generalization/inheritance/specialization, composition / containership, aggregation/ collections and associations. All of these are explained briefly below and discussed in terms of our scenario. There are some key questions associated with object oriented design over here. How data is passed between the classes? What classes should have the objects of another class?What classes create the objects of other classes?What are some of the utility classes that the application requires? All these questions play an important role in the design. Think in terms of hierarchy for generalizations/inheritence:First of all check for hierarchy that may exist between the classes or the objects.This would model the inheritance or generaliztion or the superclass/subclass relationship.In natural language this might resolve to “type of” or “can be”. If you find such words in a problem statement there might be a case of generalization. E.g. In our scenario take the three classes BOOK , REFERENCE_BOOK and ISSUEABLE_BOOK . So a book can be a reference book or an issue able book or you can say that reference books and issue able books are the type of books. They all should ideally share many characteristics which are common to all the three classes.What I mean to say is, whether it is any book (reference or issue able) they all have ISBN number, author a language, a topic e.t.c so what is the difference. The difference is implied by the business rule that reference books cannot be issued but only reviewed. So for reference books we might add a Boolean data member called m_bReference and set it to true or something. Same is the case with Member, Student_Member and Faculty_Member. Inheritance is indicated in the class diagram with a filled black triangle pointing towards the base class and connecters connecting it to all the derived classes. In our scenario the inheritance could be shown as the figure below:
Think of the Part-Whole Relationships:
Ok so now you know what might be the possible hierarchies in your system and what might be the common data members and the common functions. What are the differences and how the qualify to be another class. Another important type of relationship in terms of Object Oriented Analysis and Design is the “Part of” or “Part Whole” relationship. In Natural language, you might come across “has a” words to quickly identify these kind of relationships. In the list of candidate classes observe which of the objects the part of other objects is. This can also be taken as collection.To give you some examples for common scenarios. A Windows form is a collection of many controls.An automobile is composed of many parts.A shopping cart has many itemsA university is comprised of many campuses Here you want to ask a simple question to resolve the type of relationship and to know whether it is an aggregation or a composition. “Is the whole destroyed when the part is destroyed” or “It doesn’t make a difference to the Whole if the part is destroyed”. Now going through this example list. A form would still exist if any of the control is destroyed; the form serves it purpose properly. This implies an aggregation .An automobile wont function properly if any of its parts are destroyed e.g. it cannot function if the tires, steering, battery is taken out so this implies composition. A university will still exist if a campus is destroyed. So it depends upon the scenario and the business rules.
Returning to our depicted scenario the only part whole relationship noticeable is perhaps the catalogue. A catalogue has list of books available in the system with a short description of each. The catalogue is not destroyed if a book is destroyed so I would use aggregation in the design. In UML aggregation is shown with an empty diamond where as composition is shown with a solid black diamond.
The Uses relationship – Association:
Many objects use the methods/functions of other classes for utility. The objects are somehow related might be statically or dynamically but there is not a hierarchy or a part whole relationship. Such relationships are called association and can be mostly identified with “makes use of” or “uses” in the problem statement. E.g. There is a class called “Pen” which exposes a method called “Draw ()”. There is also a “Shape” class having a method called“drawShape ( )” . In the implementation of “drawShape( )” it internally calls / invokes the “Draw ()” method exposed by Pen. In our scenario A librarian uses the book and student information to issue a book.The catalogue needs a reference of the book to add or update itselfAnd probably some more:
Here is the sample design which I created with Visio just for the sake of discussion and show how relationships can be expressed in UML in terms of object oriented design.The business rules that I assumed for this discussion were really simple just to make the understanding better.If it helped you in any way or you require some discussion in any area do supply your feedback by leaving comments for this post. Thanks.
Database Design Tutorial
February 12, 2008
There are several different kinds of database representations. An Entity Relationship Diagram or a ER model, an Enhanced Entity Relationship Diagram EER model, Object Relational Model etc. ER Model is the most universally followed database convention at least in my experience with software application development. Any enterprise application today would surely have a database connected to it, so I think that understanding database design and to be able to design databases is a “must have” for Software developers personnel. In this article I would walk through some of the essentials to give you the basic idea by giving you an example. Once you know how it’s done in a “Non Textbook” way I guess reading the text book or some advanced tutorial would be very easy and interesting.
The First Step in ER modeling:
The first step in designing the database is to know what are the business objects or so called “Entities”. How to determine what the entities are? The textbook says Read the problem statement or the scenario and try to identify nouns. From a collection of nouns it would be much clearer to determine what the entities are in your system. No doubt it’s a text book approach. I have had very few instances where I had a problem statement and I could do a noun analysis for an object oriented or the database design. So try to think in terms of the business and ask yourself why? This is called the “ROOT CAUSE ANALYSIS”. Ask yourself the question Why the customer wants to develop this system, who would be using the system, what features should be provided and most importantly what data needs to be stored?.
E.g. If someone wants to develop an online forum and you have to design the database for them, try to think what a forum does and generate a problem statement. The requirement would be vaguely “A discussion forum has many categories. In each category there are many topics and each topic may have many messages by different users. Old messages (let’s say 10 days old) are deleted automatically by the system. User can post new messages and edit their message” what would the database design be?It is evident with the problem statement that you need to keep track of categories, messages (post) and user. An entity in the system might be a strong or a weak entity. A Weak entity is one which cannot exist on its own in a system and requires a relationship with a strong entity (the one with a primary key) to identify its records. Such an entity is described by a double lined rectangle in the model. What attributes to store? What is a primary key? What is a partial Key? What are candidate keys? What is a super key? How to select them: Simply ask yourself what is the information that the system should store for a particular entity, importantly how that information would be identified at a later time? Is there a way, an attribute which uniquely identifies any record/row/ tuple in the table? What are some of the other important attributes the system has to store?
The answer to these questions would be very important to you in terms of database design. Primarily while resolving the ER model you would be converting all your entities to tables so what are the columns of that table. They are the characteristics of the entity. e.g. In our scenario what are the important attributes of a User (in this example we only require a loginid and a password but in a slightly complex scenario like a university registration system there might be many attributes like address , phone number , date of birth , previous college , social security etc Similarly what is the data about the categories we want to store (I guess the category name , Description , we would like to know the number of messages in the category and the topic with maximum posts and stuff like that but lets not talk about that here)The set of attributes which can together uniquely identify an entity instance constitute the Super key. The minimum set of attributes (subset of super key) which can uniquely identify a record in the database is called the candidate key. There can be more than one candidate key for the entity e.g. A Student number and the Social security number we use only one as the primary key of the table and the candidate key which we use to uniquely identify any record in the system is called the Primary Key ( The programmer assigned candidate key). Note in case of weak entities the identifying attribute is called the partial key instead of the primary key.
Step 2 : What are relationships and why? What is cardinality and multiplicity?
Once you have identified the entities, all of them think of the relationships and the cardinalities or multiplicity of the relationship. For the sake of simplicity check each of the entity against all others in order to clarify the design. Start with the User. How is the user related to Categories? A user can create a new category? If yes then we have a relationship. Then there are 2 things that need to be answered.1. Can a Single User create more than 1 category2. Can a Single Category be created by more than one user These two questions are the key to determine the cardinalities which would indicate how we resolve the database design in terms of tables.The relationship can have the following cardinalities:
· 1 to 1· 1 to Many· Many to 1· Many to Many
Similarly then compare if the user and topic has a relationship. That would be pretty similar to the first one. Now also compare the user with all the other entities.Note that relationship may also have attributes like the date/time when the message was posted etc.Relationships are indicated as diamonds in the design. A relationship with one of the participating entities is weak is called a weak relationship and is indicated with a double lined diamond. Resolving Relationship in the form of physical Database design:It’s a Science not an art J So you can generate the database physical design by pushing a button given the logical design , but the logical design is not a science its an art , thankfully otherwise we would be out of business JJ.
For 1 to 1 and many to many relationships create a new table for the relationship. Include the primary key of each participating entry. The union of all the primary keys which are referenced as foreign keys can uniquely identify any record in the table. So if the cardinality of both the participating entries is the same make a separate table. However if it is not take the primary key of the entity where cardinality is 1 and include it in the table where it is many as a foreign key. This is also called an identifying relationship sometimes. I would talk a bit about the enhanced ER in my next article; hope this would help you in learning the basics of database design.Some good database design tools are Dezign for databases by datanamic, Microsoft Visio, ERWin, Rational Rose and perhaps some other free design tool. If you have any queries, suggestions or feedback I would really appreciate it.This is a sample DB Design for a STUDENT GRADING SYSTEM which is a solved exercise from “Fundamentals of Database Systems” from ELmasri/ Navathe Question 16 and Question 18 
Here is Question 18 where a new structure is to be designed that holds the previous college info , degrees and courses taken at another college:
Note: If I missed an important design concept you were looking for or is there anything you might wanna discuss ? Was this helpful to you ? I would appreciate your comments . Thanks
Remote Software Update Techniques ?
February 11, 2008
I have worked on various Self Service terminal applications so far . Kiosks for bill payment , Mini statement and balance inquiries and permit printing to self checkout solutions . One requirement that I always come across and I am not absolutely sure how and what would be the better way of solving it is remotely updating software . I want my exes and dlls to be updated and who does it ? Well it can be a windows service or any other application or perhaps a separate thread watching for the updates .
I have some experience with Microsft BITS and i wrote a wrapper for BITS in C# but all i could use the wrapper for was basically file transfer . The object didnt expose some of the core methodologies that Micrsoft uses to update windows or to install windows updates …..
So if you have worked with any such scenario where software can remotely update itself or u have a design in mind do feel free to discuss . I can provide the code whatever i have experimented , but i would really appreciate any ideas / logics or implementation that could help me make a better design for these kind of problems that i often run into … The Software/Configurations Remote update !! If u have the idea and not the time or patience to develope it feel free !! I will develope it for u !! 
If you have any experience with making installation patches without hurting the installe application . I have tried Orca editor and the msp files , thats a pain a pain in the back side …. can u think of a smarter way ? Should we write a software which does that ? If you deploy software on a regular basis i m sure you probably might have some idea for a possible work around , I am amazaed why theres nothing from microsoft , doesnt sound that complicated :$
Cheers !!
Comparison Of Pragramming Languages : Have your say ??
January 21, 2008
Programming Languages come in all tastes, shapes and sizes with their pros and cons. If you are a windows/web developer you are likely to say Microsoft.Net and if you are an open source inclined (I seriously don’t know why that would be) lolz you might have other opinion. For the sake of simplicity I would discuss the non Web development (server and client side scripting) here and would add on to my discussion in the next article. In the desktop i.e. windows and dos world having worked with C++ , VC++,VB , VB.Net , Java and C#.Net my personal favorite is definitely C#.Net. Definitely its not the best.Let me elaborate it in detail. Microsoft .Net does provide what most of the developers want. An easy way to make/change a clean UI with a great set of controls , a great collection of base classes making the day to day tasks ( File Handling , Database Handling , Exception Handling , Threads and Network programming) very easy , the scalability factor on the existing API and third party controls available , the extensive documentation and working examples that can be found everywhere , isn’t it like a dream come true .
I worked with java for some while and figured that the language is really neat , and was programming in the real sense all the way. Many people do argue that C# is more like Visual Basic with more RAD features and drag and drop support. I would say “Yes” it is but what is wrong with that? After all with all the slipping deadlines and nonexistent frameworks that’s what we are looking for. RAD features with great object oriented programming model, easy to implement the design and clean backup implementation. The problem with that however are the Portability/Compatibility issues.E.g. Whenever you want to make a product for the everyday user and publish it on the internet you have to specify that the user has to install X.X version of the framework or else your product wont work . Yes it’s a huge put off for the user and that’s one thing I don’t like about the .Net technologies. I think Microsoft can make it part of windows i.e. all standard Operating Systems by Microsoft should make sure that all the releases of .Net framework available then are installed with the operating systems. That would make the life of routine application software developers extremely easy and without having to give a link for Microsoft website to download the framework it would be simply awesome. The two problems which I find difficult when working with JAVA are the UI support and the integrated development Environment. With UI support I mean there are base classes available SWING and supporting wrapper classes but “Are they really as easy to use as the C# counterparts? No they are not!! At least to me“Now the Java lovers would argue here that there are some good and super cool IDES available like JBuilder, JCreator and Eclipse and specify the fact that they are simply great to implement Software patterns with struts and installing X.XX plug-ins on your specific IDE. What happens with that is you tend to be very specific, away from the general JAVA developer and there is not a huge community to support for your specific programming or development related issues.Same is the case when you talk about JSP and beans. Configuring the web server (Web Logic in my experience) seems to be difficult in itself and there are so many formalities to it which the new developer find difficult to adopt.With that said I would still believe that java has more pros than cons and is undoubtedly more powerful than any other programming language for application software development. It is extremely powerful and with a existing framework of UI and some good utility wrappers you just can’t beat it and Java developers are “No Wannabes”!! . They mean serious business. As far as the support and help from the existing communities are concerned try to Google a specific topic or an exact working example on C# and 8 times out of 10 you find someone in a similar situation discussing the whole issue in a forum, this is highly unlikely with C/C++ or Visual C++ and Java for that matter. Long story short I guess it’s the requirements which influence the developers or architects to opt for a particular programming language. Factors affecting the choice are usually Client requirements, hardware interfacing, operating environment, available developer’s expertise, ease of use, development costs, maintenance costs and portability. Anyways these were my views and my opinion totally off course doesn’t make things right or wrong. So if you are an active developer I would love to have your opinion on the comparison and the things on which you might agree or not? What are your views? What is your opinion? What are some of the best technologies, programming languages, development methods or sdks you have worked on ??
Aaroh Jalan Cover
January 13, 2008
This is the recording . As you know no internet and nothing to do so the empty mind =S
The Song is JALAN by AAROH
Enjoy the cool vocals and guitaring lolx :
Vacals : Me
Guitars : Me
Recorded by : ME :S
