Advantages of Network database model

The network database model extends the hierarchiear model by allowing a record to participate in multiple parent/child relationships. In order to be helpful, a database model must be able to represent data relationships in a database to mirror those we see in the real world. One of the shortcomings of the hierarchical database model was that a child record could have one and only one parent. As a result, if you needed to model a more complex relationship, you had to create redundant tables. For example, suppose you were implementing an order-processing system.

The main advantages of the hierarchical database are:

• Performance. Although the network database model is more complex than the hierarchical database model (with several additional pointers in each record), its overall performance is comparable to that of its predecessor. While the DBMS has to spend more time maintaining record pointers in the network model, it spends less time inserting and removing records due to the elimination of redundant tables.

• Ability to represent complex relationships. By allowing more than one parent/child link in each record, the network database model lets you extract data based on multiple relationships using a single table. While we explored using the network database to get a list of all customers that purchased a product and all salesmen that sold the product, you could also get a list of the orders placed by one or all of the customers and a list of sales made by one salesman or the entire sales force using the same network database structure and the same set of tables.

Unfortunately, the network database model, like its hierarchical rival, has the disadvantage of being inflexible. If you want to add a field to a table, the DBMS must create a new table for the larger records. Like the hierarchical model (and, again, unlike an SQL relational database), the network model has no ALTER TABLE command. Moreover, rebuilding a table to accommodate a change in a record's attributes or adding a new table to represent another relationship requires that a majority of the network database's record links be recalculated and updated-this translates into the database being inaccessible for extended periods of time to make even a minor change to a single table's fields.

Tags: network database model, advantages, hierarchiear model, relationships, child record, performance, complex relationships, dbms, sql, relational database, alter table,tablee

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Advantages of hierarchical databases

A hierarchical database model consists of data arranged into a structure that looks a lot like a family tree or company organizational chart. If you need to manage data that lends itself to being represented as parent/child relationships, you can make use of the hierarchical database model. Suppose, for example, that you have a home food delivery service and need to know how much of each grocery item you have to purchase in order to fill your customer orders for a particular delivery date. In a hierarchical database, each parent record can have multiple child records; however, each child must have one and only one parent.

The main advantages of the hierarchical database are:

• Performance. Navigating among the records in a hierarchical database is very fast because the parent/child relationships are implemented with pointers from one data record to another. The same is true for the sideways relationships from child to child and parent to parent. Thus, after finding the first record, the program does not have to search an index (or do a table scan) to find the next record. Instead, the application needs only to follow one of the multiple child record pointers, the single sibling record pointer, or the single parent record pointer to get to the "next" record.

• Ease of understanding. The organization of the database parallels a corporate organization chart or family tree. As such, it has a familiar "feel" to even nonprogrammers. Moreover, it easily depicts relationships where A is a part of B (as was the case with the order database we discussed, where each item was a part of an order).

The main disadvantage of the hierarchical database is its rigid structure. If you want to add a field to a table, the database management system must create a new table for the larger records. Unlike an SQL database, the hierarchical model has no ALTER TABLE command. Moreover, if you want to add a new relationship, you will have to build a new and possibly redundant database structure.

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Easy Picture Frames

A picture frame is a container added to a picture in order to enhance it, make it easier to display or, in some cases, to protect it. Picture frames are usually made of soft or hard wood although other materials are also used, including aluminum or polystyrene. A picture frame may be of any colour or texture, but gilding is common, especially on older frames. Some picture frames have elaborate mouldings on them, which may relate to the subject matter of the picture.

The picture frame may contain a pane of glass, in order to protect the picture. Glass may be treated with various coatings, the most common being UV filters. The most expensive glass, Museum glass, has a coating which makes the glass non reflective and practically invisible.

"L"-style frames are a simple variety that are constructed with a single L-shaped border of wood, with the bottom part of the L, or rabbet, at the front of the frame to hold in the glass, object and backing, which are secured in from the back. In this type a frame, a framing mat should be used to distance the object/picture from the glass, because condensation quickly accumulates inside any frame and causes damage to the picture.

Shadowbox frames have an additional channel cut into them, which the glass is inserted into. This allows the picture to be framed without a mat and still have protection from condensation.

Attractive and unique picture frames can be made with basic tools, for some only a saw and a square are needed. It is much easier to cut mitered corners with a miter box or trimmer, if the fit is not exact the angles can be fine tuned by sanding them. Often a cause of poor fitting joints is that the two opposite side pieces are not exactly the same length. A disk sander is a very handy tool to have to adjust the angles to fit, there are plans to build one here.

Miterless Frame

Make a base using 3/8" thick material as shown in fig.1, the inside dimensions should be standard photo sizes, 5 X 7, 8 X 10, 11 X 14, etc. For the top use strips 1/2" wider than base, use thicker and wider material for the corner blocks. Glue top pieces to the base as shown in Fig 2.

Rather than using corner blocks, cut strips 3/8" wider and glue on top of base lapping the joints as shown in Fig. 3

Traditional Molding Profiles

Clamping

There are several ways to clamp your frames, perhaps the easiest way is to use a picture frame clamp. There are manufactured ones available or you can build your own. Masking tape will also work, simply lay a strip around each corner to hold it together until the glue sets. Rubber bands cut from innertubes can be used but it is difficult to keep the parts together while stretching it around the frame.

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Eliminate Credit card debt

A poor credit history can make it harder for you to rent an apartment, buy a car, or fulfill a dream. It is important to know how credit can change your spending power and how you can recognize the danger signs of credit and avoid serious problems.

The problem arises when people tend to use their credit card for almost every expenditure from grocery, accessories, entertainment to children's toys. Soon they find themselves facing a severe cash crunch, unable to pay back their card dues, and forced to borrow from friends and relatives.

There are several people out there who use their card like there's no financial tomorrow. Don't forget that as soon as you roll the bill over, the interest clock starts to tick.

Warning signs

Your card does not give you credit for free. And once you allow the outstandings to pile up, the sum can pose as much danger to your financial security. It's the same old addiction thing. You can get as addicted to irresponsible spending as you can to drugs or alcohol.

So, first admit that there's a problem. The symptoms are easy enough to detect: huge credit card statements, plenty of unused clothing and gizmos, a wallet full of ATM receipts and charge slips and, the worst, a savings bank account with no savings.

Credit cards can reduce your future buying power if you carry a balance and let finance charges build up.

You are in trouble if:

• You reach for your card automatically when you don't have cash.
• The monthly statement you receive has several expenses you could have avoided.
• You pay just the minimum due on your credit cards each month.
• You use the cash advances facility regularly, often to pay off other debts.

• You use one credit card to pay off the bills on another card.

If one or more of the above apply to you, you are headed for serious trouble. Still not convinced? Calculate the sums you paid over the years in credit dues, interest and late payment fees: they will add up to a fortune.

How can you get rid of your credit card debt?

Financial freedom can be yours if you exercise some willpower and take a few basic steps to eliminate debt.

• The first thing to do is get all your credit card bills together. For each account, write down the total balance and the minimum monthly payment required. Prioritize your repayment.

• The next step is to be sure you can make the minimum payments on your credit cards. Look at your spending and make cuts where you can to find the money to pay your credit card bills.

• Call the bank today and ask for a lower credit limit. Once that's done, you won't be able to charge as much on your card, and will be forced to use it only when absolutely necessary.

• If you have already used your card to the hilt, keep lowering the limit as and when you pay off the balance. Also if your interest liabilities are huge, consider transferring your balance to a low-interest card. The difference of even half a basis point in interest can save you a few thousand rupees in payments.

• Make it a priority to pay off your credit card bills. If need be, use your savings to bring your outstandings to zero. Once you eliminate the debt, make sure you pay your card dues in total each month.

• Don't put off settling your dues for another day. The more you delay, the more the bills will mount. 'Decide How Many Credit Cards You Need' and 'Decide How Much Credit Is Too Much.' Choose strategies to cut your debts as soon as possible.

• Pay off cards with the smallest balances first. Paying off cards with small balances gives you extra money to pay on the bigger balances. Once you pay off a bill, next month add the amount you have been paying to the check you write to your remaining creditors.

For example, let's say you pay Rs 350 a month on your Citibank account. Once it's paid off you can start adding Rs 650 to the check you write to pay your ICICI account. Then when you've paid off your VISA, add that amount, including the Rs 350 from the Citibank account, to the check you write to pay your MasterCard account, and so on until all the accounts are paid in full.

• Stop making new charges. If you have to, cut up your cards, hide them, or lock them in a drawer. The key to sticking to your credit card debt repayment plan is to stay flexible.

• If you find that you set unrealistic spending limits in the beginning, revise your spending plan the next month. Find one or two low-rate cards and cancel all the others. Switching from a high-rate credit card to a low-rate card can easily save you Rs 20,000 or more a year.

• Carry just what you need. Most people need only one or two credit cards one for purchases they pay off each month, and another for emergencies (or business purposes). Any more than that is usually overkill.

• Get some free stuff. If you're going to use it anyways, why not get something back for your trouble? If you consolidate your spending on one card, consider getting a 'rewards' card where you earn miles, stuff, or cash back on your spending. Look for a card that will award you stuff you'll actually use.

• Cash is usually a good option. Still, don't let your spending get out of control just so you can get a free travel bag or a few extra airline miles.

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Tags: credit card, credit card debt, eliminate credit card debt, atm, charge slips, savings, statement

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Validator controls for Checkbox and Checkboxlist in asp.net

ASP.NET provides a variety of validation Web controls that can be used to validate a user's form field inputs. (See Form Validation with ASP.NET - It Doesn't Get Any Easier! for general information on the validation Web controls and Dissecting Validation Controls in ASP.NET 2.0 for the validation control changes from ASP.NET version 1.x to ASP.NET version 2.0.) Unfortunately, the validation Web controls do not work with the CheckBox or CheckBoxList Web controls. If you set a validation control's ControlToValidate property to the ID of a CheckBox or CheckBoxList, the page will throw an HttpException, stating: "Control 'controlID' referenced by the ControlToValidate property of 'validationControlID' cannot be validated."

There may be times, however, when you need to provide validation for a CheckBox or CheckBoxList. Many Web pages with Terms of Service include a CheckBox titled "I agree to the above terms" that must be checked before continuing. Likewise, a Web Form may contain a set of options in the form of a CheckBoxList. Perhaps the user is required to check at least one of these options before continuing. To provide such validation, we have three choices:

1. Forgo any sort of validation Web control semantics and perform the validation check using code on postback. The downside of this is that it breaks from the standard validation control metaphor and requires extra effort to include client-side validation.
2. Use the CustomValidator control and define our own server-side and client-side validation logic. The benefit of this approach is that it adheres to the validation control metaphor; however, the validation logic is tightly bound to the ASP.NET page, meaning that the server-side and client-side validation must be replicated on all pages that need to validate a CheckBox or CheckBoxList. (See Using the CustomValidator Control for more information on this topic.)
3. Create a custom, compiled validation server control that provides the functionality needed. The benefit of this approach is that we have a reusable, easily deployable custom server control that adheres to the validation control metaphor. Unfortunately, this option requires the most upfront code/effort. 

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Tags: validator controls, checkbox, checkboxlist, asp.net, web page, form validation, user controls

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Issues and problems with Windows XP Service Pack 2

Did you ever experience issues while installing Service pack 2 of Windows XP?. To all the users who had problems installing service pack 2 has a solution.

Product IDs that matches one of the following (where X is any numeric value): XXXXX-640-0000356-23 XXX or XXXXX-640-2001765-23 XXX will be blocked from installing the service pack as they were blocked from Service Pack 1 (Click here for how to view your product id). If you have brought what you believe to be a legal version of Windows go back to where you purchased it and ask for a legal product key.

In order to install SP2 you will need a legal version of the Windows XP Edition you are currently using, insert the CD into your drive before Windows loads and boot from the CD (may require this function to be enabled in your computers BIOS). Once Windows XP setup has begun press Enter to start setup and press F8 to agree to the EULA. Select the current windows install to repair and press R. This will give you the ability to change the pirate key with a new legal retail key.

If you have the following problems, follow the link.
- Service Pack 2 Will not install, I'm told I have an invalid product key
- Service Pack 2 Setup could not verify the integrity of the file. Make sure the Cryptographic service is running
- When trying to upgrade to a later version of SP2 with a Beta or Release Candidate version already installed setup is terminated
- Atapi.sys is currently in use, please close all programs and continue.' Warning Message shown during setup

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Tags: windows xp, service pack 2, problems sp 2, issues sp 2, invalid key, microsoft

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Create Tool tips using CSS easily

As you have surfed the web you have probably run into pages that had a nifty tool-tip that would come up when you hovered over a word. These tool-tips are being used more and more by web designers to display the definition of a word or the long version of an acronym. There are other uses as well but you will figure those out on your own, I just want to show you how to add these CSS tool-tips to your pages. He is a snippet of code that will show a CSS tool-tip. After checking out the code, try hovering over the example text below the code.

<span title="This is a CSS tool-tip" style="cursor: help;">Hover Here</span>

Hover Here

You should see that the cursor changes to a question mark when you hover over the text. You can style the text however you wish but it helps to make the style stand out a bit so that the user knows that the text has something different about it. Most web designers use the following style for text that has a CSS tool-tip.

<span title="This is another CSS tool-tip" style="cursor: help; border-bottom: 1px dashed #000000;">Another Example</span>

Another Example

With the dashed border underneath the text your users will know that there is something about the text that is different from the rest of the text so they will most likely hover their mouse over it and see the CSS tool-tip come up. If your regular links are underlined with a solid line then users will know that text underlined with a dashed line is different from a link.

You can make the text for your tool-tips pretty long and most browsers will still show them. Firefox is the only browser (as far as I can tell) that truncates the tool-tip to a shortened length. The other browsers I have tested will display a much longer tool-tip although I am sure they have a maximum limit too. I have tested these tool-tips in IE, Firefox, Opera, and Konquerer. Please let me know how they work in other browsers specifically if there is a problem.

You may also wish to learn how to use Javascript to create tool-tips on your pages.

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Tags: css, css tool tips, create tooltips, span, tooltip example

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Javascript location.reload simple example script

Many web pages on the internet are dynamically generated using PHP or some other scripting language. Dynamically generated pages can provide the website's visitors with up to the minute information that static pages cannot. There are some pages that visitors refresh often because of the data they contain. For example, pages with stock quotes, news, auctions, statistics, sports scores, and bank accounts all have data that can be changed at any second. The Javascript location.reload function gives your visitors an easier way to reload the page.

There are a few different ways to implement the location.reload function. You can provide a simple link that the user can click on to call the Javascript function or you can use a timer that calls the location.reload function at a specified interval.

Here is an example of how to use Javascript's location.reload in a link:

<a href="javascript:location.reload();">Refresh the page</a>

The above HTML is pretty simple and easy to understand. When the user clicks the link the page will reload or we could say, refresh. It basically does the same thing as the user's refresh button in their browser but they don't have to drag their mouse pointer all the way up to the refresh button, instead they just use your "Refresh the page" link.

The other method of using location.reload which involves a timer is a little more complex. You will need to place the following code in the <head> section of your webpage or in an external Javascript file.

<script type="text/javascript" language="javascript">
var reloadTimer = null;
window.onload = function()
{
    setReloadTime(5); // In this example we'll use 5 seconds.
}
function setReloadTime(secs)
{
    if (arguments.length == 1) {
        if (reloadTimer) clearTimeout(reloadTimer);
        reloadTimer = setTimeout("setReloadTime()", Math.ceil(parseFloat(secs) * 1000));
    }
    else {
        location.reload();
    }
}
</script>

So when the page gets loaded, a timer is set for five seconds in this example. After five seconds the location.reload function is called and the page will reload. You can change the five to whatever you want to make the delay as long or as short as possible.

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Tags: javascript, location.reload, dynamic, php, reload page, javascript example, script example

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A simple Javascript function to get URL parameters

Most of the server-side programming languages that I know of like PHP, ASP, or JSP give you easy access to parameters in the query string of a URL. Javascript does not give you easy access. With javascript you must write your own function to parse the window.location.href value to get the query string parameters you want. Here is a small function I wrote that will parse the window.location.href value and return the value for the parameter you specify. It does this using javascript's built in regular expressions. Here is the function:

function gup( name )
{
  var regexS = "[\\?&]"+name+"=([^&#]*)";
  var regex = new RegExp( regexS );
  var tmpURL = window.location.href;
  var results = regex.exec( tmpURL );
  if( results == null )
    return "";
  else
    return results[1];
}

The way that the function is used is fairly simple. Let's say you have the following URL:

http://www.foo.com/index.html?bob=123&frank=321&tom=213#top

You want to get the value from the frank parameter so you call the javascript function as follows:

var frank_param = gup( 'frank' );

Now if you look at the frank_param variable it contains the number 321. The query string was parsed by the regular expression and the value of the frank parameter was retrieved. The function is smart in a couple of ways. For example, if you have an anchor in your URL like our example URL above does (#top) the gup() function knows to stop before the # character. Also, if a requested parameter doesn't exist in the query string then an empty string is returned instead of a null.

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Tags: javascript, url parameters, get url parameters, server side, window.location.href, javascript function

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Javascript location.reload simple example script

Many web pages on the internet are dynamically generated using PHP or some other scripting language. Dynamically generated pages can provide the website's visitors with up to the minute information that static pages cannot. There are some pages that visitors refresh often because of the data they contain. For example, pages with stock quotes, news, auctions, statistics, sports scores, and bank accounts all have data that can be changed at any second. The Javascript location.reload function gives your visitors an easier way to reload the page.

There are a few different ways to implement the location.reload function. You can provide a simple link that the user can click on to call the Javascript function or you can use a timer that calls the location.reload function at a specified interval.

Here is an example of how to use Javascript's location.reload in a link:

<a href="javascript:location.reload();">Refresh the page</a>

The above HTML is pretty simple and easy to understand. When the user clicks the link the page will reload or we could say, refresh. It basically does the same thing as the user's refresh button in their browser but they don't have to drag their mouse pointer all the way up to the refresh button, instead they just use your "Refresh the page" link.

The other method of using location.reload which involves a timer is a little more complex. You will need to place the following code in the <head> section of your webpage or in an external Javascript file.

<script type="text/javascript" language="javascript">
var reloadTimer = null;
window.onload = function()
{
    setReloadTime(5); // In this example we'll use 5 seconds.
}
function setReloadTime(secs)
{
    if (arguments.length == 1) {
        if (reloadTimer) clearTimeout(reloadTimer);
        reloadTimer = setTimeout("setReloadTime()", Math.ceil(parseFloat(secs) * 1000));
    }
    else {
        location.reload();
    }
}
</script>

So when the page gets loaded, a timer is set for five seconds in this example. After five seconds the location.reload function is called and the page will reload. You can change the five to whatever you want to make the delay as long or as short as possible.

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Tags: javascript, location.reload, dynamic, php, reload page, javascript example, script example

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Foundations of AJAX (Foundations) ebook

Ajax burst onto the Web development scene by offering highly interactive, desktop-like Web applications that can be deployed through any modern Web browser without the need for special plug-ins. Ajax is built on existing Web technologies such as JavaScript, HTML, and CSS, and it is used in conjunction with your favorite server-side language. Foundations of Ajax explains how to combine these technologies effectively to implement Ajax into your new or existing Web applications. Like you, we are developers who are "in the trenches," tasked with building Web-enabled applications that provide real value to our customers. As the Web continues to grow, the demand for more expressive and engaging interfaces will continue to increase.
Much of the early hype surrounding Ajax centered on its use by Internet powerhouses such as Google and Amazon. However, just because the initial forays into Ajax were pioneered by leading software development firms doesn't mean your application wouldn't also benefit from these techniques. You already know how to develop Web applications, so this book uses specific, focused examples to teach the Ajax tools and techniques you'll need to bring your applications to life. Armed with this book and your existing development expertise, you too will be able to apply Ajax techniques to your application to enrich the end user's experience.
When we first saw the potential of Ajax, we knew we had to start leveraging it for our own applications. Along the way we've learned some hard-earned knowledge that we thought needed to be shared with the rest of the development community. With this book you'll be able to easily extend your own applications with Ajax and have fun while doing it. We hope that someday we'll be reading about your great Ajax-enabled application!

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Ajax Professional Programmer to Programmer ebook

Written for experienced web developers, Professional Ajax shows how to combine tried-and-true CSS, XML, and JavaScript technologies into Ajax. This provides web developers with the ability to create more sophisticated and responsive user interfaces and break free from the "click-and-wait" standard that has dominated the web since its introduction.
Professional Ajax discusses the range of request brokers (including the hidden frame technique, iframes, and XMLHttp) and explains when one should be used over another. You will also learn different Ajax techniques and patterns for executing client-server communication on your web site and in web applications. By the end of the book, you will have gained the practical knowledge necessary to implement your own Ajax solutions. In addition to a full chapter case study showing how to combine the book's Ajax techniques into an AjaxMail application, Professional Ajax uses many other examples to build hands-on Ajax experience. Some of the other examples include:

• web site widgets for a news ticker, weather information, web search, and site search
• preloading pages in online articles
• incremental form validation
• using Google Web APIs in Ajax
• creating an autosuggest text box

Professional Ajax readers should be familiar with CSS, XML, JavaScript, and HTML so you can jump right in with the book and begin learning Ajax patterns, XPath and XSLT support in browsers, syndication, web services, JSON, and the Ajax Frameworks, JPSpan, DWR, and Ajax.NET.

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Java J2EE Job Interview Questions ebook

A Java/J2EE technical job interview guide for job seekers, promotion seekers, pro-active learners and interviewers. Learn the core concepts and issues relating to Java/J2EE in an easy to understand questions and answers approach . Covering over 220 interview questions and answers on: Java, J2EE, Applet, Servlets, JSP, EJB, JNDI, RMI, JDBC, LDAP, JMS, XML, RUP, UML, STRUTS, SQL, Design concepts & design patterns, JUnit, Ant, CVS, Development process, Emerging technologies/frameworks like AOP, IoC, Hibernate, Spring, JSF and more.

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Automatically generate HTML and javascript from server side code

Automatically generate HTML and Javascript from server-side code. You write code in a standard server-side language like Java, or a custom language like that used in Backbase, and it's converted to HTML and Javascript. Depending on the framework, you might not need to code directly in HTML or Javascript at all. Since you're unlikely to create such a framework yourself, this pattern relies on a certain category of publicly availably Ajax Framework.

In the case of all code being autogenerated, the code is something like a conventional desktop application. Widgets and event-handler are defined, and the browser generates the appropriate HTML, along with XMLHttpRequest Calls and general Javascript handling. As well, the framework will often generate Ajax Stubs to deal with incoming calls and pass them to appropriate application code.

In other frameworks, the approach is more mixed. The framework might let you create a Slider with just a single tag, for example. But in the tag, you'll specify a Javascript function to be called whenever the slider value changes.

There are several arguments for Server-Side Code Generation:

• Developers don't have to know HTML and Javascript. One nasty thing about the web paradigm is that developers usually have to learn HTML, CSS, and Javascript on top of any server-side languages. Along with the raw language, each of these languages has its own conventions, patterns, and libraries to get familiar with. It's not surprising that few people master both sides. Server-Side Code Generation allows developers to focus their attention only on the server-side language.
• The framework can, in theory, handle graceful degradation transparently. In other words, it can free the developer of worrying about browser portability, Javascript or cookies being turned off, or XMLHttpRequest Calls timing out.
• The framework can, in theory, deliver multiple platforms simultaneously. A single code base can be used to generate a web application (Ajaxian or not), standalone desktop application, and maybe even a mobile application.

However, code generation does comes at a cost to usability. Look at it this way: anything you could generate from the server, a skilled developer could also hand-code. The reverse is not true; given enough time and talent, it's always possible to build a custom solution that's superior in terms of usability. So, to be worthwhile, the framework must add enough value in terms of productivity and support for non-experts, to compensate for the drop in usability. Whether this can be achieved really depends on two things: how much users will gain from a custom-built application; and how much of a boost the framework will give you. On the second point, consider a few counter-arguments to the benefits above:

• The first point, about developer's not having to learn HTML and Javascript, has traditionally been the most compelling. Server-side developers have produced minimal satisficing, rather than optimal, interfaces, allowing them to focus on the server side. It's not uncommon to see advice against anything relatively complex being performed on the server-side. But as Ajax becomes more prominent, this argument becomes less compelling. As discussed in Fat Client, Javascript is undergoing a renaissance - developers will learn about it, tools and libraries will evolve, patterns will emerge. All of this reduces the argument for isolating developers from HTML and Javascript.
• A server-side framework may well be able to handle graceful degradation and browser versions transparently. But to the extent that's possible, a browser script can also achieve the same effect, as discussed in Cross-Browser Component.
• The dream of transforming a single code into a variety of different user-interface styles has been around for a while. Certainly, many modern UI toolkits are cross-platform, running on different operating systems from the same code base. However, can a single code base lead to both a web application and a desktop application? It's possible in theory and in proof-of-concept demos. But, in practice, users expect applications to follow the conventions of the platform and that's difficult to achieve with a single generation. It might, however, work if the framework allows for platform-specific tailoring.

Full-featured frameworks will likely be more prominent on intranet applications, where new functionality is often more critical than usability, and users can be trained to work around problems. Hand-coded HTML and Javascript is more likely for public dot-coms where alternatives are abundant and the pressure of competition means its critical to optimise the user-interface. In those environments, there is still some role for Server-Side Code Generation, but mainly as a helper for very specific tasks and with some flexibility, rather than as the overarching architectural style.

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Tags: ajax, ajax patterns, design, http, javascript, generate html, server side code, developers, java, ajaxian, web application, xmlhttprequest, server

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Need for AJAX Patterns

Ajax holds a lot of promise for web usability, and the underlying technology has already delivered some stunning applications. But it's no magic bullet. Careful design is always required, and it target the technology at hand. As Ajax emerges, we're going to learn more about what sort of design works, and we'll need ways of documenting this information and talking about it. Fortunately, the evolution of this particular technology will take place at a time when design patterns are well-entrenched in the industry, and design patterns are an excellent means of knowledge representation. Thus, it makes sense to begin cataloguing Ajax design patterns. These are some thoughts based on current examples and demo systems.

Patterns being patterns, nothing in here is truly new. Patterns are just a concise way to represent the knowledge embodied in the many Ajax applications that are out there. The point is to discover best practices by investigating how developers have successfully traded off conflicting design principles. Ajax is all about usability, so the patterns focus particularly on delivering usability in the face of constraints, most notably: user capabilities and expectations, bandwidth limits, the stateless nature of HTTP, the complexity of Javascript.

There should eventually be more patterns, more examples, more detailed explanations. And one more disclaimer: Ajax is a new term, but XMLHttpRequest and related technologies have been around for a while. I know that, but the introduction of a single umbrella term nevertheless constitutes a tipping point which is forcing web development to move heavily in a certain direction. Ajax is only a name, but names can be tremendously important.

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Tags: ajax, ajax patterns, design, http, javascript

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Add Windows media player to a HTML page

This piece of HTML code adds a Windows media player into the HTML page. The versions of 7,9 and 10 of windows media player will work without any problem. The following code has some parameters.

Useful Parameters:
autoStart=true;
baseURL (Specifies the base URL used for relative path resolution with URL script commands that are embedded in media items.)
currentPosition (default=0; Specifies the current position in the media item in seconds.)
enabled=false (Specifies whether the Windows Media Player control is enabled.)
URL (Specifies the name of the media item to play.)
uiMode (Specifies which controls are shown in the user interface. Possible values: invisible, none, mini, full.)

<object id="VIDEO" width="320" height="240" 
    style="position:absolute; left:0;top:0;"
    classid="CLSID:6BF52A52-394A-11d3-B153-00C04F79FAA6"
    type="application/x-oleobject">
    
    <param name="URL" value="your file or url"/>
    <param name="SendPlayStateChangeEvents" value="False"/>
    <param name="AutoStart" value="True"/>
    <param name="uiMode" value="none"/>
    <param name="PlayCount" value="9999"/>
    <param name="Volume" value="9999"/>
</object>

<object id="VIDEO" width="320" height="240" 
    style="position:absolute; left:0;top:0;"
    classid="CLSID:22D6F312-B0F6-11D0-94AB-0080C74C7E95"
    type="application/x-oleobject">
    
    <param name="URL" value="your file or url"/>
    <param name="SendPlayStateChangeEvents" value="False"/>
    <param name="AutoStart" value="True"/>
    <param name="uiMode" value="none"/>
    <param name="PlayCount" value="9999"/>
    <param name="Volume" value="9999"/>
</object>

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Different Software development process models

Software engineering follows some structured models for software development. A Software Model describes the phases of the Software Life Cycle and the order in which those phases are executed.  The following sections discuss the following important process models:

· Waterfall Model

· Iterative Model

· Incremental Model

· Spiral Model

Waterfall Model

This is the most common, easy to implement and classic of all the life cycle models. It also is referred to as a Classic Life Cycle Model or linear-sequential life cycle model. This model places a lot of emphasis on documentation, i.e. Requirements Specification and Design Document. In a waterfall model each phase must be completed sequentially in its entirety before the immediate next phase can begin. A review is done after each phase to analyze whether the project is running as per the required standards, specifications and timelines.

The output of each phase is the input to the immediate next phase in this model. This model is well suited if the project requirements are static or have been clearly stated from the beginning. The Waterfall Model is great for specifying the individual tasks, roles, and deliverables in the project life cycle. It is a misleading model when used for project planning because it de-emphasizes iteration and incremental delivery.

Advantages of the Waterfall Model

The following are the advantages of the Waterfall Model.

· It is very simple and easy to implement meaning it is well suited for small projects.

· Testing is inherent to each of the phases of this model.

· The model is rigid and each of the phases has certain deliverables and a review process immediately after a particular phase is over.

Disadvantages

The following are the disadvantages of the Waterfall Model.

· It is high risk.

· It cannot be guaranteed that one phase of this model is perfect before we move on to the immediate next phase in the model.

· It is not suited for long or complex projects or projects where the requirements can change.

· The deliverable software is produced late during the life cycle.

Iterative Model

The Iterative Model addresses many problems associated with the Waterfall Model.  In the Iterative Model analysis is done the same way as it is done in the Waterfall method.  Once this analysis is over, each requirement is categorized based on their priority.  These priorities are:

· High

· Low

· Medium

Advantages

The advantages of the Iterative Model are:

· Faster Coding, testing and Design Phases

· Facilitates the support for changes within the life cycle

Disadvantages

The disadvantages of the Iterative Model are:

· More time spent in review and analysis

· A lot of steps that need to be followed in this model

· Delay in one phase can have detrimental effect on the software as a whole

Incremental Model

The incremental model divides the software to be developed into modules which are then developed and tested in parallel.  These modules or cycles are divided up into smaller, easily managed iterations.  Each iteration passes through the requirements, design, implementation and testing phases.  The Incremental model allows full SDLC of prototypes to be made and then tested before moving to next level.  In this model the functionality is produced and delivered to the customer incrementally.  Starting from the existing situation, we proceed towards the desired solution in a number of steps.  At each of these steps the Waterfall Model is followed.

Advantages

The following are the advantages of the Incremental Model.

· Deliverables are produced early in the software development lifecycle in each iteration.

· It is flexible and easy to manage

· Risk Management and Testing is easy

Disadvantages

The following are the disadvantages of the Iterative Model.

· Each phase of iteration is rigid and does not overlap each other.

· All the requirements are not gathered up front for the entire software life cycle which can create problems at the later stages in the design and development cycle.

Spiral Model

The Spiral Model or the Spiral Development Model combines the best of both top down and bottom up approaches and is specifically risk-driven.  It combines the features of both the prototyping and the waterfall models.  In essence the Spiral Model is a combination of the classic Waterfall Model and Risk Analysis.  It is iterative, but each iteration is designed to reduce the risk at that particular stage of the project.  The Spiral Model provides a rapid development and at the same time, incremental versions of the software application.  The Spiral model is better than the Waterfall Model in the sense that it emphasizes more on risk management while the Waterfall Model emphasizes more on the project management aspects.

The spiral model has four phases.  These phases are as follows:

· Planning

· Risk Analysis

· Engineering

· Evaluation

Advantages

The following are the advantages of the Spiral Model.

· It has strong support for Risk Analysis.

· It is well suited for complex and large projects.

· The deliverable is produced early in the software development life cycle.

· It uses prototyping as a risk reduction technique and can reduce risks in the SDLC process considerably.

Disadvantages

The following are the disadvantages of the Spiral Model.

· It is high in cost and Risk Analysis is also very difficult.

· It is not suited for small projects.

· Needs considerable Risk Assessment.

Which Model to choose?

The question that now arises is, "Which model should I choose?"  Note that we should choose the right type of the Model to implement based on the scope of the software project.  This depends on a number of factors, some of which are given below.

· The Scope of the Project

· The Project Budget

· The organizational environment

· Available Resources

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Tags: sdlc models, process models, waterfall, iterative, incremental, spiral, life cycle, software engineering, software model, phases, advantages, disadvantages, review model, priorities, deliverables, testing, design, implemenation, documentation

 

 

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Steps in Software Development Life Cycle SDLC

Software Development Life Cycle (SDLC) is a methodology that is typically used to develop, maintain and replace information systems for improving the quality of the software design and development process.  The typical phases are analysis, estimation, design, development, integration and testing and implementation.  The success of software largely depends on proper analysis, estimation, design and testing before the same is implemented.

Steps in SDLC

The Software Development Life Cycle is the cycle in which the business analysts, the software developers, the database designers and/or the database developers, the QA developers and end users collaborate to build the application software.  Basically, it involves designing the application from scratch, documenting everything, adding the improvements and fixing the bugs that occur in the SDLC.  It is the lifecycle of Software from concept to obsolescence.

A quality software system is based on the following three principles:

· Modeling of the software development process (process)

· Modeling of the measurement of product (product)

· Modeling of the management and human interactions (people)

The software development life cycle (SDLC) may be divided into the following steps:

1. Requests from customers/original idea

2. Creation of feature lists based on item 1

3. Technical design of features based on item 2

4. Software design and time evaluation based on item 3

5. Code implementation based on item 4

6. Software Testing

7. Beta release/ bug fixes

8. Final release

SDLC Categories

Broadly, the SDLC steps discussed earlier can be categorized into:

· Requirement Specification

· Requirement Analysis and Design

· Coding and Testing

· Deployment and Support

The following sections discuss these in more detail.

Requirement Specification

Software Requirements Specification (SRS) provides a complete description of all the functions and specifications of the software to be designed.  It extracts the functional and the nonfunctional requirements of the desired software product.  It is the initial stage in the SDLC, the first and the foremost step that has to be performed and includes the information about the requirements for the proposed system.  The requirements are pertained to such as resources, scope of the system, purpose of the system and the limitations.  This phase is also known as the feasibility study phase.

Requirement Analysis and Design   

After the requirements specification is over, it is analyzed for its accuracy and sufficiency.  Issues such as whether that particular proposed system will serve the purpose or not, what are the necessary constraints that have to be taken into consideration and the monitoring the management of the activities in a fashion are all carried out in a hierarchical manner which is specified in the BRS (Business Requirement Specification) document.

Coding and Testing

The next step consists of developing the application logic and writing the functionalities for the user interfaces on a specific action performed (known as Coding).  The coding or the development phase takes as its primary input the design elements described in the approved design document. It is to be noted that the Programmers/Developers should adhere to the required coding standards.  The code should also be optimized for the purpose of saving the valuable resources. Next in the SDLC cycle comes the testing phase.

Deployment and Support

The software that has been developed and deployed should provide adequate support for maintenance so as to cope with the bugs that can exists even after deployment of the software is over.  This can take far more time than the initial development process of the software.

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Tags: sdlc, process models, development process, analysis, estimation, design, development, integration, testing, implemenation, life cycle, quality software, request

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Simple tip to become successful

Is there magic in the number 48? Does this number hold any significance in your future success? Speaker Don Crowther suggests that there is. In his presentation at the NSA Summer Symposium, Don told the audience that 48 minutes is the magic number. Here’s how it works… Set a timer for 48 minutes. Close out all distractions and work continuously for 48 minutes. When the timer goes off, get up and stretch, get coffee, use the restroom etc, in the following 12 minutes. Repeat as necessary.

Don reports that this technique repeated four times a day allowed him to write a 200 page book in just two weeks. The ability to focus on one task for 48 minutes straight was the key. I have been testing Don’s idea and I have to say it works well for me. This eliminates the distractions that have a way of derailing even the best laid plans. Taking a short 12 minute break once an hour is refreshing but not enough to get you off track.

So the question comes up, If this solution works well how can I use it in planning out my daily schedule and applying it to future goals. Can I successfully write a blog post in 48 minutes? Can I write a book chapter in that time? As I’ve tried the process, it has been a challenge to sit in one place that long. But when I do my productivity soars. I find it best to just keep writing, not worry about mistakes, and get everything on paper. Once I have the points on paper I can go back and make my edits and corrections.

My usual morning schedule has about 2 hours of productive time available. I’ve tested the idea of blogging for an hour and then working on a book for the second hour. So far this has worked well with standard length blog posts and has yielded a book outline.Check out this article for further information

Tags: magic number, simple tip, successful, future, distractions, be productive, office, get energized

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Handling Exceptions and errors in ASP.NET

Exceptions or errors are unusual occurrences that happen within the logic of an application. You cannot program for every possibility; hence, they are imminent. If an exception occurs within an application, the user is presented with a yellow page that looks ugly. So, how do you deal with these situations? You use exception handling techniques in ASP.NET.

There are three ways to handle exceptions/errors in ASP.NET:

1. try-catch block. This is also called Structured Exception Handling (SEH).
2. Error Events.
3. Custom Error Page.

You will look at each one of them in detail in the next sections.

try-catch Block

Enclose code that accesses files, databases, and so forth inside a try-catch block because access to those resources might be denied due to various reasons causing an exception. The third part of this block is finally. It is executed irrespective of the fact that an exception has been raised. Hence, use the finally block to complete the housekeeping jobs.

As a good programming practice, always catch specific exceptions. To view the exception types supported by the .NET Framework, use the Debug menu and select Exceptions in Visual Studio.NET.

In the following code, you try to access a table that does not exist in the Northwind database; therefore, an exception is raised. By using the try catch and finally block, you handle the exception and display a message.

try
{
   con = new SqlConnection("integrated security=SSPI;
      data source= (local);persist security info=False;
      initial catalog=Northwind");
   da = new SqlDataAdapter("Select * from TblNotExisits", con);
   ds = new DataSet();
   da.Fill(ds);
}
catch(SqlException ex)
{
   return "Connection Unsuccessful " + ex.Message;
}
finally
{
   con.Dispose();
}
return "Connection Successful";

Using Error Events

There are three different error events in ASP.NET that can be used in conjunction with SEH so that all exceptions are handled and the user is presented with a user-friendly error message.

1. 
   
   Page_Error: Occurs when an error occurs within the Web page. This event is in the Web form.
   
   
2. 
   
   Global_Error: Occurs when an error occurs within the application. This event is in the Gloabl.asax file.
   
   
3. 
   
   Application_Error: Occurs when an error occurs within the application. This event is in the Gloabl.asax file.

Methods in the Server object are used to handle the exception in the error events.

1. 
   
   GetLastError: Gets the last exception that occurred on the server.
   
   
2. 
   
   ClearError: Use this method to handle the exception and stop the error to trigger the subsequent error event or display the error to the user.

In the following code, you handle the exception in all the above three mentioned events but call the ClearError method only in the Application_Error event so that the error is propogated to the above level.

private void Page_Error(object sender, System.EventArgs e)
{
   Exception ex = Server.GetLastError();
   Response.Write("Handled error from Page<br>");
   //Server.ClearError();
}
protected void Application_Error(Object sender, EventArgs e)
{
   Exception ex = Server.GetLastError();
   Response.Write("Handled error from Application <br>");
   Server.ClearError();
}
protected void Global_Error(Object sender, EventArgs e)
{
   Exception ex = Server.GetLastError();
   Response.Write("Handled error from Global <br>");
}

Using Custom Error Pages

Use custom error page to handle HTTP exceptions such as page not found, unauthorized access, and so forth. You can specify custom error pages in two places:

1. 
   
   customErrors section of the web.config file. This setting specifies the application-wide error page to display for unhandled HTTP errors. HTTP errors are identified by the HTTP status code. Include the <error> tag in the customErrors to display a status code-specific error page. Does not work with .htm or .html files. Set the mode attribute to "On" to view the error page locally.
   
   
2. 
   
   errorPage attribute of the @Page directive of the Web form to display the error page for the error generated on the particular Web form.

The customsError section in the web.config file specifies the application to redirect to Error404.aspx file if a non-existent file is requested.

<customErrors mode="On" defaultRedirect="Error.aspx">
   <error statusCode="404" redirect="Error404.aspx" />
</customErrors>

The @Page directive specifies the error page to be redirected to if an error occurs in the Web page.

<%@ Page language="c#" Codebehind="PageErr.aspx.cs"
         AutoEventWireup="false"
         Inherits="ExceptionHandling.PageErr"
         errorPage="Error.aspx" %>

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