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My team is developing an appraisals software for real estate on an enterprise level. This application has some special requirements.
The application should work in Online and Offline environment. If the user is working and suddenly Application goes offline User should be able to work offline. All offline work is stored in local database and sync next time to a central database when Application connects to the internet.This application has many users and all will work at the same time on same information.
User local database must be updated all times either other users are working or not. If other users are working all updated information should be available in the local database to ensure when the user goes offline all information is updated.
The question is How to develop this kind of application? Is there any standard way to achieve this target? Is there any standard or non-standard pattern to build this kind of software?
We are planning to use the Angular 2 Framework for our front end development. If anyone has experience with this and can give suggestions on what tech stack we should use, it would be greatly appreciated.
Well, you can use pouchdb as client-side DB and use every DB that uses the CouchDB sync protocol. I have used this stack with an Angular 2 application. (NoSQL)
I also worked with Kinto (PostgreSQL) and Kinto.js. It is not as user-friendly as PouchDB, but I think the documentation has improved since I used it.
And finally, I know about Meteor/Mongo/GroundDB. Meteor is very powerful it's a fully reactive Stack which works really well with the async options you have with angular and rxjs. But think if you have not worked with rxjs or reactive backends it's the hardest to learn. I took me a long time to adapt my coding style to the reactive Behavior of the data flow.
We are also doing an online POS that would work as a point of sale
but we are in constant backend solution for us to set up database that can sync or scale with offline and online .
Im developing a 'Multi-User' app and considering using the new(ish) chrome packaged app platform but I have a local database question.
As I understand it (correct me if im wrong), I can store data locally with IndexedDB, but this is exclusively run on the users browser so is only relevant to that user, any changes can only sync when the user is on-line (needing an internet connection).
My app must adhere to the 'offline first' model but as each local user is located in the same physical office on a local network, id like these users to be able to share and sync the applications data without an internet connection (in case its gone down). Meaning we don't bring the whole office down if internet fails, a sort of 'off-line multi user' model.
Is there a way for a chrome packaged app to store data on an internal local database, or am I going about this the wrong way?
You could use sockets to interact with your local network, but if I had to do it, i would use a local web server as a fallback when the internet connection is offline.
That would be a pretty neat feature. Unfortunately, there aren't any web APIs (or Chrome Apps APIs) that specifically facilitate peer-to-peer communication. As xmarcos says, the primitives are there for you to build it yourself, but it would be a pretty big undertaking.
Also one correction to your question: IndexedDB doesn't sync unless you build a syncing infrastructure on top of it yourself. You might be thinking about chrome.storage.sync. However, even in that case, the syncing is replicating only a user's own data, not doing a collaborative merge of multiple users' data into a single repository. You seem to be wanting the latter, and for that you're on your own.
You might be interested in reading more about distributed version control. Here's one concise description of a complicated topic.
What are the strategies you employ to let multiple people work on an access database?
Is it possible to host it online and have its features still functional without having to develop a custom frontend?
MS Access as a software has a few nice features that don't require any programming to configure:
Drop down lists - choose one
Multi Checkbox lists - choose multiple
Is it possible to get all of these features available even when hosted online? I'm basically thinking of an alternate way to quickly get people to work with data using GUI features like the above without going the webapp<>MySQL way.
You have some good comments here. Keep in mind that things have changed quite a bit for access 2010.
Access 2010 allows you to build web applications. The development process is very much the same as it’s been for years, but you can’t use VBA in forms for these web applications (you use a new macro language). This new feature set allows you to publish applications you build to a website. Here is an video of an application of mine running in access 2010, and at the halfway point in the video I switch to running the access application 100% in a web browser:
http://www.youtube.com/watch?v=AU4mH0jPntI
The above is for access 2010…due out this year. The above will require you to be running SharePoint services, or use an hosting service that supports "access web" services.
For previous versions of access, for all intents and purposes, it’s not a web based system at all. Now when you say multiple users, you have to clarify what kind of users and where they plan to be. If your users are on a local office network, then MS access can be used as a multi user system right out of a box with no additional coding and programming required. It is recommended however that you split your application into a front end part that’s deployed on each user’s computer. This Concept as outlined in the following article of mine.
http://www.members.shaw.ca/AlbertKallal/Articles/split/index.htm
Now, perhaps the users are going to be on notebooks and in different locations all over the country? In this type of case you are attempting to connect over a wide area network, or have users connect to the application over the Internet. This is a different problem. In this type of scenario, a good solution is to use something like SQL server for the backend, and you continue to deploy the Access front ends to each user’s computer. This application tends to be about the most cost affordable also. And using sql server + ms-access means you get to continue developing in Access for the most part like you always done. Another way to accomplish wide area use without resorting to sql server is to use something called terminal services. I outline these possibilities in the following article:
http://www.members.shaw.ca/AlbertKallal//Wan/Wans.html
As mentioned, a few others here posted links to some of the new SharePoint features that you can consider using, but they not out untill later this year.
Multi-user Access apps are pretty easy to do for small workgroup user populations in the 15-25 ranger or smaller. Above that, a developer should consider upsizing to a server back end, with the trade-off being greater administrative overhead for the server vs. having to program the app more carefully if you retain the Jet/ACE back end.
As to online access, you this isn't possible over HTTP, but if you have a Windows Terminal Server available, you can host your app there and give users access to that. This is actually an extremely easy and efficient and inexpensive way to support remote users of an app, though the larger the user population, the more problematic it becomes. But by the time an Access app has a user population that would strain a Windows Terminal Server setup, you're no longer going to be using a Jet/ACE back end.
And with a server back end, you could give access to a SQL Server on a VPN over the Internet, and if you write your Access app really efficiently, even over a standard broadband connection, your users could still work productively.
Then there's the future of Access: in Access 2010, a great deal of work has been done to integrate with a host of new features in Sharepoint 2010. If you create your A2010 app using the new type of Access web forms and reports, your app can be uploaded to a Sharepoint server running the new Access Services, and it can then be used running in a web browser (not limited to IE and not dependent on any plugins or web controls, as was the case in the past with the completely worthless Access Data Access Pages). The data store can either be a SQL Server, or you could keep it Jet/ACE for users not accessing it via the web browser, and have the data stored in Sharepoint for the online users. Also, you can have an app integrated with Sharepoint running locally in Access that uses Sharepoint when connected to the Internet, and still be able to work offline when disconnected. When connected again, you synch your local changes with the Sharepoint server, resolve any differences and continue working.
The features are really quite remarkable, and according to what I've heard and seen, if the Access app is built entirely of web forms and reports, it will look and function identically when run in Access and when run in the web browser via Sharepoint. And if you need to have client-side features that you don't expose to the users running the app in the browser, you can still use traditional Access objects!
The Access development team's blog has a number of posts on what's coming in A2010, and there's a good video posted there demonstrating how A2010 integrates with Sharepoint 2010's new Access Services.
This constitutes a quantum leap in Access's web capabilities, which were previously almost non-existent, and I'm quite excited about this. I was formerly quite wary of the changes being made to Access that seemed entirely to make it a servant of Sharepoint, but now I can see that the benefit to Access users and Access developers will be huge.
One way i've heard of, is to import the access database into a SQL Server database.
(Almost any version will do.).
Then link to the SQL Server database with Access and let users use it as they did before.
Look at this link: http://office.microsoft.com/en-us/access/HA010345991033.aspx
If you want an online solution i'd recommend going with a normal web application architecture. (Talking to a proper database.).
I have never needed to support it myself, but from what I heard so far, performance dramatically breaks down as soon as you need to support multiple users writing simultaneously. I think this is because Access uses simple file locking to implement isolation, and this just is not the right technique for a concurrent database system.
Hosted on-line? Do you mean on the network? Technically it will work on a network but there is a reason MS-Access in not in Visual Studio - it is not considered a development platform - it is a desktop application. When MS-Access first hit the scene many people built applications using it. The multiuser functionality just is not there. Upto four or five users is ok. But I would not go for more.
I am asking this in very general sense. Both from cloud provider and cloud consumer's perspective. Also the question is not for any specific kind of application (in fact the intention is to know which type of applications/domains can fit into which of the cloud slab -SaaS PaaS IaaS).
My understanding so far is:
IaaS: Raw Hardware (Processors, Networks, Storage).
PaaS: OS, System Softwares, Development Framework, Virtual Machines.
SaaS: Software Applications.
It would be great if Stackoverflower's can share their understanding and experiences of cloud computing concept.
EDIT: Ok, I will put it in more specific way -
Amazon EC2: You don't have control over hardware layer. But you can take your choice of OS image, Dev Framework (.NET, J2EE, LAMP) and Application and put it on EC2 hardware. Can you deploy an applications built with Google App Engine or Azure on EC2?
Google App Engine: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing Java or Python application and port it to GAE? Or vice versa, can applications that were built on GAE be taken out of GAE and ported to any Application Server like Websphere or Weblogic?
Azure: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing .NET application and port it to Azure? Or vice versa, can applications that were built on Azure be taken out of Azure and ported to any Application Server like Biztalk?
Good question! As you point out, the different offerings fit into different categories:
EC2 is Infrastructure as a Service; you get VM instances, and do with them as you wish. Rackspace Cloud Servers are more or less the same.
Azure, App Engine, and Salesforce are all Platform as a Service; they offer different levels of integration, though: Azure pretty much lets you run arbitrary background services, while App Engine is oriented around short lived request handler tasks (though it also supports a task queue and scheduled tasks). I'm not terribly familiar with Salesforce's offering, but my understanding is that it's similar to App Engine in some respects, though more specialized for its particular niche.
Cloud offerings that fall under Software as a Service are everything from infrastructure pieces like Amazon's Simple Storage Service and SimpleDB through to complete applications like Fog Creek's hosted FogBugz and, of course, StackExchange.
A good general rule is that the higher level the offering, the less work you'll have to do, but the more specific it is. If you want a bug tracker, using FogBugz is obviously going to be the least work; building one on top of App Engine or Azure is more work, but provides for more versatility, while building one on top of raw VMs like EC2 is even more work (quite a lot more, in fact), but provides for even more versatility. My general advice is to pick the highest level platform that still meets your requirements, and build from there.
This is an excellent question. Full disclosure as I am partial to Azure but have experience with the others.
Where I think Azure stands out from the others is the quick transition from on prem to the cloud. For example -
SQL Azure - change connection string, upload DB, go!
Queues work a lot like MSMQ.
Blobs are pretty much blobs any way you shake them but they scale like crazy.
The table storage component is good because it provides incredible scalability for name/value pairs - but takes some getting used to.
Service Bus is my favorite of the services because it allows for a variety of communications paradigms. Two SB endpoints first try to connect to each other, if they cannot, then they route through the cloud - makes for very secure and scalable processing when firewalls tend to get in the way.
Access control list - paired typically with the service bus to make sure the right people access the right things - think SAML in the cloud.
I hope that helps!
My cloud experience is currently limited to Salesforce.com
For standard business operations and automation it provides a significant number of features that allow us to get apps up and running very quickly. We are particularly benefitting from the following:
Security (Administrators can control access to objects and fields)
Workflow & Approvals
Automatic UI generation
Built in reporting and dashboards
Entire system (including our custom changes) is accessible via web services
Ability to make the data in the system available through public sites (e.g. eCommerce)
Large library of third party apps to solve standard problems
The platform does NOT solve every problem.
I would not use the platform to model a nuclear power station or build the next twitter.
The major points of cloud computing is to save on costs by paying for usage and enable immediate deployment of computing resources.
The costs are not purely x amount of cents per instance per hour. The costs include maintenance, development, administration, etc. The huge benefit of cloud, in my mind is to liberate the customers from having to manage anything that is not within the realm of their core business competency. If I am an insurance business, I want my developers to concentrate on my insurance problems that help solve needs of my claims, rates, etc. I would rather avoid dealing with problems of email servers, file servers, document repositories, and administrating OS patches, service packs, etc.
Thus, in my opinion, the biggest benefits are derived from the SaaS and PaaS cloud offerings. One should go to IaaS only when PaaS or SaaS have serious restrictions to specific needs (i.e. I need to install a set of proprietary COM components and Azure does not support them).
SaaS is good for commodity type of applications that are not the core line of business for the client, but are more of a utility. These are your typical Messaging systems, Portals, Document Repositories, Email systems, CRMs, ERP's, Accounting, etc. etc. etc. Why reinvent the wheel by writing your own when you can customize a well supported third party product.
PaaS is great for core line of business software that supports companies' main business offering. Abstracts clients from having to deal with OS management and lets clients concentrate on the business system development - something that noone else can do for the client.
One can also take advantage of the benefits of PaaS (let's say, Google App Engine) and extend it, at times and if necessary, by pulling out some virtual machines from IaaS providers (e.g. Amazon) to do some number crunching then just send back the output to Google App Engine.
This way, you get the best of both worlds -- you can rapidly develop scalable apps in GAE, then you can always augment it by running any program you want from Amazon virtual machines.
This keeps changing, now Windows Azure also supports VM, so it is also an IaaS provider now.
Now how about Free Amazon EC2 for a year to do a better comparision. Check this out.
http://www.buzzingup.com/2010/10/amazon-announces-free-cloud-services-for-new-developers/
I am going to write a database application for the camp I work for. I am thinking about writing it in C# with a Windows GUI interface but using a browser as the application is seeming more and more appelaing for various reasons. What I am wondering is why someone would not choose to write an application as a web application. Ex. The back button can cause you some trouble. Are there other things that ayone can think of?
There are plenty of cons:
Speed and responsiveness tend to be significantly worse
Complicated UI widgets (such as tree controls) are harder to do
Rendering graphics of any kind is pretty tricky, 3D graphics is even harder
You have to mess around with logins
A centralised server means clients always need network access
Security restrictions may cause you trouble
Browser incompatibilities can cause a lot of extra work
UI conventions are less well-defined on the web - users may find it harder to use
Client-side storage is limited
The question is.. do enough of those apply to your project to make web the wrong choice?
One thing that was not mentioned here is the level of complexity and knowledge required to generate a good web application. The problem being unless you are doing something very simple, there is no "Single" knowledge or technology that goes into these applications.
For example if you were to write an application for some client server platform.. you may develop in Java or C++. For a complex web application you may have to have expertise in Java, Java Script, HTML, Flash, CSS, Ajax, SQL, J2EE.. etc. Also the components of a web based application are also more numerous, Web Application Server, HTTP Server, Database, Browser.. are tipical components but there could be more.. a client server app is tipical just what it says.. a client application and a Server application. My experience and personal preference is not web based .. web based is great for many things. But even though I am an IT Architect for a leading company that is completely emersed in Web Apps as the solution for everything... The cons are many still.. I do thing the technology will evolve and the cons will go away over time though.
Essentially the real limitations are only through of the platform, being the browser. If you have to account for all browsers in current use that can be a pain due to varying degrees of standards in each of them.
If have control of the which browser to use, that is everyone is on computers that you control on site, and say you install firefox on all of them, you could then leverage the latest Javascript and CSS standards to their fullest in your content delivery.
[edit] You could also look into options like the adobe integrated runtime or "AIR" as an option allowing you to code the front-end with traditional browser based options like xhtml/css/javascript, flash/flex and have the backend hooked up to your database online, only also providing functionality of a traditional desktop app at the same time.
The biggest difference and drawback I see with web applications is state management. Since the web is, by nature, stateless every thing you want to maintain has to be sent back and forth from the server with every request and response. How to efficiently store and retrieve it in a matter with respect to page size and performance is hard to do at times. Also the fact that there is no real standard (at least not that everyone adheres to) for browsers makes consistency really..........fun.
You need to have a network access to the server that you are going to have the web application on (if there are going to be multiple users for the application - which is typically the case).
Actually, there are more pros than cons - if you can give some details about your application, we could help a little more...
It completely depends on the requirements of your project. For the most part, there isn't much web applications cannot do these days. Admittedly, certain applications do belong on the desktop as browsers (while currently advancing, and rapidly), still are not quite there yet. From the advent of applications such as Google Docs, Gmail
There isn't much you -cannot- do on the web. If you're creating a World of Warcraft competitor however, the web is most certainly not the optimal solution. Again, unfortunately we'd need more insight on the application you're building for the camp. The best part about the web is that anyone with a browser can use your application.
Web applications delegate processing to a remote machine. Depending on the amount of processing, this can be a con. Consider a photo editor that's a web app.
Web applications also can't deal with a whole lot of data going back and forth to and from a client. You can watch video online.. when it's compressed. It will be awhile before we see any web-based video editing software.
Browser compatibility is also a hassle. You can't control the look-and-feel of the application 100%.
Vaibhav has a good point. What's your application?
A major one is down time for migrations... users will not expect the application to be down, ever, but realistically it will have to be down for major upgrades. When doing this with a desktop application, the user (or end-user systems admin) is in control of when upgrades happen; with an online app, they're not.
For applications which have large data, performance can be a major problem as you're storing a large number of users' data centrally, which means the IO performance will not be as good as it would be if you gave them all a laptop.
In general scalability gives problems for a server-based app. Desktop applications scale really well.
You can do an awful lot with a web-based app, but it is a lot easier to do certain things with a thick client:
Performance: You get simple access to the full power of the client's CPU.
Responsiveness: Interactivity is fast and easy.
Graphics: You can easily use graphics libraries such as DirectX and OpenGL to create fast impressive graphics.
Work with local files
Peer-to-peer
Deciding whether a web application is a good approach depends on what you are trying to achieve. However here are some more general cons of web applications:
Real integration with desktop apps (e.g. Outlook) is impossible
Drag and drop between your app and the desktop / other running apps
With a web application, there are more privacy concerns, when you are storing user data on your servers. You have to make sure that you don't loose/disclose it and your users have to be comfortable with the idea of storing that data on your servers.
Apart from that, there are many security problems, like Man-in-the-middle attacks, XSS or SQL injections.
You also need to make sure that you have enough computing power and bandwidth at hand.
"Ex. The back button can cause you some trouble."
You'll have to be specific on this. A lot of people make fundamental mistakes in their web applications and introduce bugs in how they handle transactions. If you do not use "Redirect after Post" (also known as Post-Redirect-Get, PRG design), then you've created a bug which appears as a problem with the back button.
A blanket statement that the back button in trouble is unlikely to be true. A specific example would clarify your specific question on this.
The back button really is not that much of an issue if you design your application correctly. You can use AJAX to manipulate parts of the current page, without adding items into the browser history (since the page itself wont change).
The biggest issue with designing web applications has to do with state, and the challenges that need to be programmed around. With a desktop application, state is easy to handle, you can leave a database connection opened, lock the record and wait for the user to make the changes and commit. With a web application, you could lock the record...but then what if the user closes the browser? These things must be overcome in the design of your application.
When designing a web application, make sure that each trip to the server "stands alone" and provides a complete answer. Always re-initialize your variables before performing any work and never assume anything. One of the challenges I ran into once was pulling "pages" of grid data back to the user. In a real busy system, with record additions/modifications happening in real time, the user navigation from page to page would vary greatly, sometimes even resulting in viewing the same set of a few records as new additions were added in-front of the query.