Hi everyone I’m new to server-side technologies so maybe this is a bit of a dumb question but after reading dozens of articles and viewing dozens of videos I’m still very confused. This has to do with arquitecture principles of modern apps.
Relational model:
I know that a few years ago the model was to have a database (mostly relational) and a DBMS that enabled the connection between an app and the database.
Question 1: Since we are talking about a relational model some examples of DBMS’s are MySQL or PostgreSQL?
Question 2: What is the process of information exchange? The client-side uses a language like PHP to make a request to the server and then the DBMS transforms the request into SQL and accesses the database? Is the conversion of the PHP into SQL part of DBMS function or another server-side software is needed?
(If someone could provide me summary detailed explanation I would be very thankful)
Non-Relational Models:
Question 2: Nowadays with the rise of NoSQL models does the same concept of DBMS apply? Since these systems allow other querying language other than SQL there should be some piece of software that has this function?
Service Oriented Arquitecture:
Almost every app uses this type of arquitecture. I understand the concept of avoid the creation of too tight software relation between client and server side allowing for multiple use across several platforms. What I don’t understand is what parts constitute a system that is build this way.
Question 3: Does the DBMS provides the API’s that constitute the web services made available?
Web Frameworks:
Last but not least, where do frameworks like Django or Ruby on Rails land on?
Question 4: These are supposed to provide tools to develop everything between the front-end and the database of a SOA system right?
Question 5: I’ve seen a lot of buzz about REST arquitecture. Can you explain me of the querying process happens and what are the software entities involved.
Thank you in advance for any explanation that helps me understating these questions. Please provide some links or any diagrams that you find useful.
EDIT:
I'll tackle your questions individually:
Question 1: Since we are talking about a relational model some examples of DBMS’s are MySQL or PostgreSQL?
Correct. The Database Management System is the suite of software that lets you interact with a particular database technology. The examples you give are correct.
Question 2: What is the process of information exchange? The client-side uses a language like PHP to make a request to the server and then the DBMS transforms the request into SQL and accesses the database? Is the conversion of the PHP into SQL part of DBMS function or another server-side software is needed?
There are many different avenues for this. Typically the API for accessing a database is done via ODBC (Open Database Connectivity). ODBC drivers are available for most (if not all) Relational DB vendors and are all very similar.
A language like PHP could connect to the database via an ODBC connection library (eg http://php.net/manual/en/intro.uodbc.php) which would allow you to send CRUD operations to the DBMS to be executed on the database.
Since most DBMS's use a subset or superset of a SQL standard for querying the database you can either pass this code directly via ODBC or you may use another level of abstraction. A common method is called an ORM (Object Relational Mapper). ORMs (eg SQLAlcmehy for Python: http://www.sqlalchemy.org/) provides an abstraction layer so you're not reliant on writing SQL but instead write queries and database commands in a format more common of your language of choice.
Question 2: Nowadays with the rise of NoSQL models does the same concept of DBMS apply? Since these systems allow other querying language other than SQL there should be some piece of software that has this function?
Same general concept (in that there is a DB Driver that exposes an API that languages can hook into) but there are generally more and differing ways of interacting with DB's now since they have many differing structures. Most NoSQL DBs still have ODBC connectors (eg MongoDB and Hadoop) so the general programming practices still apply whilst connecting with them, but the things you expect the database to do (and their natural query languages) will differ.
This continues to be an evolving space as these technologies evolve.
Question 3: Does the DBMS provides the API’s that constitute the web services made available?
Not sure I'm understanding this question. ODBC and webservices are different. Often webservices sit on top of ODBC if you want to query a database via a web API, but it's one layer of abstraction more than connecting to the DB directly via ODBC.
Last but not least, where do frameworks like Django or Ruby on Rails land on?
Web Frameworks are a way of quickening the development of web applications by trying to stop some of the "reinvent the wheel" things that you commonly do with every web application. They give you the basics, and have a lot of extensions that allow you to implement other common elements of web apps (like a subscription/login system, session management, admin system etc).
These are supposed to provide tools to develop everything between the front-end and the database of a SOA system right?
Both Django and RoR aim to be end-to-end frameworks. They include all the common elements you'll need including an Object Relational Mapper. They don't prescribe which DBMS you have to use, their ORMs can interface with many so that choice is still up to you.
Yes, they are aimed to cover everything from the front end to the DB, including the interaction with and initialization of the structure of the database.
Question 5: I’ve seen a lot of buzz about REST arquitecture. Can you explain me of the querying process happens and what are the software entities involved.
REST stands for Representational State Transfer (quick Wikipedia article: https://en.wikipedia.org/wiki/Representational_state_transfer). In a nutshell the creation of a "RESTful" (REST compliant) web API would mean that you have GET, PUT, POST and DELETE methods to accomplish all your services. REST aligns closely with the HTTP protocol which is why it's been very appropriate for the ever growing concept of Web Apps, it's helped transform the thinking from a Web Page (or set of web pages) into Web Apps.
It's hard to sum up better than the Wikipedia article does, I'd suggest you dive into it.
Hope that's cleared up a few of the questions!
I have hadoop 1.0.4 running on my ubuntu 11.04,configured with eclipse I want to make a web application to run hadoop jobs, or may be Cassandra,Hbase and Hive might be a way but I don't have much time to learn thoroughly all these and I want to do it as quickly as possible.Any advice which one might prove the easiest to get started with ?
I don't know if this question really qualifies to be here on SO in its current form. This is the reason I did not write this initially. But, a lot of SO experts are out there to decide this(they can do it much better than me) :)
Having said that, I would like to share a few things with you based on my personal experience, so that you proceed towards the correct path. First of all, Hadoop jobs(MapReduce) and Hive are actually not a good fit for web services kinda use cases. They are most suitable for offline, batch processing kinda stuff. HBase/Cassandra can be used though, if you have real time needs(like web services).
Coming back to your actual question. Before diving into Hadoop, Hive, HBase etc, I would suggest you to get some hold on web services first(if you are new to web services as well). Reason being, a web service is something which has much wider scope of applicability as compared to tools like Hadoop, Hive, HBase etc. These tools are specific to some particular use cases and cannot be used everywhere. But, web services are used almost everywhere and with n number of different things, like RDBMSs, NoSQL datastores etc etc. So if you know web service concepts you definitely have that extra edge. To begin with you can visit these links :
Web Services Tutorial by W3Schools(Nice n easy. Would serve the quick start guide purpose).
For a detailed tutorial you can visit the oracle web services tutorial.
This link by IBM developerworks has references to some really good web services learning stuff.
You might find this one really helpful to start with(Shows how to create web services using Eclipse).
And you can obviously Google web service tutorials anytime.
One last thing. Although it's not mandatory to be a pro in things like Hadoop, Hive, HBase etc, but having some decent amount of understanding of the concepts would be really helpful in developing your solution in a much better manner. It'll allow you to think accurately in the correct direction.
HTH.
I know there are plenty of threads on when you should/shouldn’t use ORM. But at my level of “expertise” I’m far from qualified to be able to tell whether or not my app would be better off with or without ORM. And I don’t want to wait till I’m proficient enough to figure out whether I should learn ORM or not.
So could you tell me whether or not most of today’s web service apps (and most of web apps in general) are being written using ORM?
PS - I'm learning WCF and Asp.Net Web forms
I guess a lot of webapps (yes, probably most of them) use some orm persistence layer these days, provided they use a relational database. That goes for java (hibernate, jpa), .net, Python, groovy/grails and Rails (ActiveRecord by default).
There are also more and more orm solutions appearing for non-relational data stores.
It certainly depends on the language and application framework you are using, if any.
I'm wondering if anyone is currently utilizing Microsoft's Master Data Services? How you are utilizing it? Whether you find it useful? When you believe it would be useful? Thanks!
I have been working with MDS since it was first released as part of a feature pack for SQL Server 2008 R2. While MDS has some compelling features - most notably detailed data lineage, I am not confident in recommending it to clients yet.
My reason for this hesitation is the nature of the install and the tendendency to fail on upgrade or system change. I struggled mightily with the both the SQL Server 2012 RC0 MDS and the RTM installs. There are simply too many brittle aspects of the install (such as the hard requirement that the service be installed on a domain-joined machine and the need to install the Silverlight 5.0 SDK for the client to work properly). I also experienced flakiness in the the Excel add-in.
I see where Microsoft is going and I think the product will eventually be useful. Considering it's purpose (master data repository), MDS must be more 'rock solid' before I would use it in production.
We aren't using it currently in our office, however the presentation Microsoft did in town a while back seemed very interesting. I saw it as sort of a competitor to Oracle's OBAW warehouse. You've probably already looked at these, but Microsoft has a decent set of webcasts that cover how to install and use MDS out here:
http://www.msdev.com/Directory/SeriesDescription.aspx?CourseId=155
I'm anxious to see if anyone else is using it as well, we tend to have a hard time talking our management into letting us try these types of services without being able to point to other corporations that have successfully implemented said product.
We're just starting to investigate the use of MDS to support our consulting practice, specifically around data analytics and ETLs to deduplicate, standardize, and sanitize client data. It's probably just scratching the surface of MDS, but we were led to MDS initially for its inclusion of regular expression capabilities in SQL to transform free-form text data.
Before MDS/DQS, part of the sustainability / enduring-success of a custom database application was heavily dependent on one or both of the following items...
Having a full-time technical resource to manually update the master data. Someone who can work with the Business Experts and make the necessary adjustments to the data in the database.
Developing (in addition to the database/application/etc) a custom UI that is intuitive enough for the less-technical Business Experts to use for managing the master data themselves.
Neither of these were ideal from a cost-perspective. With MDS/DQS, a developer/contractor can come in, design an end-to-end Data Warehouse/BI solution including full integration with DQS/MDS (probably via SSIS packages) with relative ease. The Business-Experts can be trained to manage the master data using a UI they are already very familiar with (ex. Excel), and the developer/contractor can move on to the next project/client.
Also, if the business already has other data sources (via acquisitions or silo'd-yet-overlapping efforts or whatever), MDS can be used to manage all the master data in one centralized location.
It might not be the best MDS product available yet however it does come with SQL Server. Compared to most of the bespoke efforts for accommodating meta-data or master data in warehouse loads it's a pretty good option since most of the time is spent concentrating on the warehouse and the mastering of ancillary or other data isn't normally well accommodated for leaving questionable results. I prefer to use it than create some other flaky option that the customers will find it difficult to maintain. If you have budget however I would consider looking around for something more polished.
Like anything though give master data the respect it deserves. If it is going to be used then it's worth spending the time to model the entities, flow of data and usage correctly. The data stewards will need to savvy and will require training (it's not the most usable interface in the world - to say the least).
As we are a small consulting and development company we don't use MDS internally but we do implement it at customers with a focus on managing the Golden Record as the customers have a myriad of databases and applications all using the same data (customer, product …)
I agree with Lynn Langit's comment about installation and SilverLight dependency and the general comments about the UI. There are also a lot of smaller companies that don't run SQL Enterprise Edition but whom could benefit from MDS.
Those are the reasons why we are now developing a modern web application which we will host for our customers (probably on Azure).
If you're thinking about MDS I'd recommend to have a look at the API to replace (parts) of the UI.
Master Data Service is very useful for managing Master Data,
We have used Master Data Services 2012 and 2016, there are not too many features present in 2012 ,2016 is much better than 2012 with some new features , but I think still Microsoft needs to improve Master Data Services, they should include some flexibility in business rule's area.
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Okay, I will shortly be starting down the path of windows mobile development. I know nothing about the subject really and I am looking for people with experience to let me know of any gottchas you may know of.
Right now I dont even have a breif of what is requied but the assumption is that the application will be very little more than a bunch of CRUD forms for updating data. The only other requirment knowladge I have is that the application will need to support offline storage when there is no signal avaliable. This in turn will obviously require some kind of syncronization when signal returns.
My initial thoughts are that the application will primarily be a front end to interact with a web service layer. Im assuming that WCF will be an appropriate technology for building these services? I also thought that SQL Server CE would be a good route to go down with regards to the offline storage issues.
Any knowlage that you feel is useful within this domain would be appreciated. Advice, links, books anything appreciated.
EDIT: It has been noted that there are two ways to go with off-line synchronization. To either use some form of message queuing or to use SQL synchronization tools. Could anyone offer a good comparison and introduction to these?
EDIT 2: After a little more digging I get the impression that there are basically 3 different approaches I can use here:
Emmbeded Database to query against then syncronization online, when able
MSMQ along with .NET remoting
WCF with ExchangeWebServiceMailTransport bindings using Exchange Server.
Now, there has been a nice few points raised on the first issue, and I think I understand at some level the issues I would face. But I'd like to get a little more information regarding MSMQ implementations and using WCFs new bindings.
Here a few words from my experience so far (about 9 months) of .net Windows Mobile development.
Well you are occasionally connected. (Or more likely occasionally disconnected). You have to choose whether you are going to use messaging with queues (i.e. WCF/SOAP/XML or something like it) or database synchronisation. I choose the SQL synchronisation route so I can't really comment on messaging. The SQL synchronisation route is not hassle free!
If you go down the sync route with SQL compact like me you basically have two choices. SQL Server merge replication or the newer ADO.NET Synchronisation services. If you choose the former you need to be really careful with your DB design to ensure it can be easily partitioned between mobile subscribers and the publisher. You really need to think about conflicts, and splitting tables that wouldn't normally be split in a normalised DB design is one way of doing that. You have to consider situations where a device goes offline for some time and the publisher DB (i.e. main DB) and/or a subscriber alters the same data. What happens when the device comes back online? It might mean resolving conflicts even if you have partitioned things well. This is where I got burnt. But SQL Merge Replication can work well and reduces the amount of code you have to write.
Roll your own DAL. Don't attempt to use datareaders etc. directly from UI code and don't use typed datasets either. There may be third party DALs that work with Windows Mobile (i.e. I know LLBLGEN does, might be worth a look) but Linq-to-SQL is not supported and anyway you need something lightweight. The chances are the DAL won't be too big so roll it yourself.
If you are using .net you'll probably end up wanting some unimplemented platform features. I recommend using this inexpensive framework to give you what your missing (especially as related to connectivity and power management) - http://www.opennetcf.com/Products/SmartDeviceFramework/tabid/65/Default.aspx
Windows Mobile devices partially switch off to save power when not in use. If you are doing a polling type design you'll need to wake them up every x mins. A normal .net timer class won't do this. You'll need to use a platform feature which can be used from OpenNetCF (above). The timer class is called LargeIntervalTimer and is in the OpenNetCF.WindowsCE assembly/namespace (I think).
Good Luck!
SqlCE is only one of the options available for local data storage on a Windows Mobile device, and although it's an excellent database it has limitations. For one thing, SqlCE will not work (period) under encryption (in other words, if your user encrypts the location where your SDF file is, you will no longer be able to access the data).
The second (and most critical) weakness of SqlCE lies in the RDA/Merge Replication tools. SqlCE Merge Replication is not 100% reliable in situations where the network connection can drop during replication (obviously very common in Windows Mobile devices). If you enjoy trying to explain missing or corrupted data to your clients, go ahead and use SqlCE and merge replication.
Oracle Lite is a good alternative to SqlCE, although it too doesn't work properly under encryption. If encryption is a potential problem, you need to find a database engine that works under encryption (I don't know of one) or else write your own persistence component using XML or something.
Writing a WM application as a front end that primarily interacts with a web service in real time will only work in an always-connected environment. A better approach is to write your application as a front end that primarily interacts with local data (SqlCE, Oracle Lite, XML or whatever), and then create a separate Synchronization component that handles pushing and pulling data.
Again, SqlCE merge replication does this pushing and pulling beautifully and elegantly - it just doesn't work all the time. If you want a replication mechanism that works reliably, you'll have to write your own. Oracle Lite has something called a snapshot table that works very well for this purpose. A snapshot table in Olite tracks changes (like adds, updates and deletes) and allows you to query the changes separately and update the central database (through a web service) to match.
This thread I just posted on SO a few days ago has proven to be a great resource for me thus far.
Also the Windows Mobile MSDN WebCasts are a wealth of information on everything from just getting started up to advanced development.
I would suggest Sqlite for local storage. From the last benchmark I ran it was much better than SqlCe and you don't have to do stupid things like retain an open connection for performance improvements.
Trade-offs being that the toolset is less rich and the integration with other MSSql products is nil. :(
you might want to refer to this:
getting-started-with-windows-mobile-development
You shouldn't be intimidated for windows mobile development. It isn't much different from desktop development. I strongly recommend that you use .NET Compact Framework for development and not C++/MFC.
Some useful links:
Mobile section at the Code
Project. You would find a lot of
articles, a little digging is needed
to find the appropriate one.
Smart
Device Framework from OpenNetCF
offer valuable extensions to the
compact framework.
When you install
the Mobile SDK, you will find under the
Community folder links for the
Windows Mobile and CF framework
blogs. These are also valuable
resources.
Regarding your application, you are right about the WCF and the SQL Server CE. These are the proper ways for handling communication and storage.
Some hints for people coming from a desktop world:
You need to have some sort of power management. The device may automatically go to suspend state. Also, you shouldn't consume power when you don't have to.
Network connectivity is a difficult issue. You can register notifications for when a specific network (Wi-Fi, GPRS) becomes available or unavailable. You can also set the preferred means of communication.
Make the UI as simple as possible. The user uses his thumb and/or a pen and he is probably on the move.
Test in a real device as early as possible.
"24 Hours of Windows Mobile Application Development" from the Windows Mobile Team Blog has some good resources
If you can, try to start from the user use cases and work back to the code, rather than vice versa. It's really easy to spend a lot more time working on the tools than working on the business problem. And thinking through user requirements will help you consider alternate strategies, because a lot of the patterns you know from normal .NET don't apply.
I've done lots of intermittent application development of exactly the type you are describing, and an on-board database works just fine. The MSMQ/WCF stuff just adds conceptual overhead without adding much value. You need a logical datastore locally anyway, and replication at this level is a simple concept that you want to keep simple, so the audit trail is easily monitored and debugged. MSMQ and WCF tend to hide things in unfamiliar places.
I upvoted the SqlLite suggestion BTW. MS doesn't have their persistence story stabilized yet for CE.
For the database replication bit I highly recommend Sybase Ultralite. In terms of flexibility and performance it knocks the socks off SQL CE
I had to do this once. Weird setup with Macs for development, and we were all Java programmers. And a short deadline. PowerPC macs too, so no chance to install Windows for Visual Studio development, never mind that the money for this would never have appeared.
We ended up writing applications using Java, running on the IBM J9 virtual machine, with SWT for a user interface. Entirely free development stack. Easy to deploy. Code ran on any platform we desired, not just PocketPC/WinMob.
Most of the work was on the server side anyway - the database, the web service server. The logic. The reporting engine. The client side wasn't totally simple however - would get the form templates from the server (because they changed frequently), the site details (multi-site deployment), generate a UI from the form template (using some SWT GUI components that are wonderful for PocketPC development, like the ExpandBar), gather data with a point and click interface (minimising keyboard entry where possible), and then submit it back to the server.
For offline storage we used XML files on the device itself. More than enough for our needs, but yours may differ. Maybe consider SQLite?
There are a couple links you can check out to start with:
http://developer.windowsmobile.com
http://msdn.microsoft.com/en-us/windowsmobile/default.aspx
If you have a sticking point while developing, there are also Windows Mobile dedicated chats on MSDN that you can attend and ask your questions. The calendar hasn't been updated yet, but the next ones should be in January. You can find the schedule here: http://msdn.microsoft.com/en-us/chats/default.aspx
I am going to add an additional question to this post, as its been active enough and hopefully will be helpful to others as well as me. Ok, so after playing around I now realize that standard class libraries cannot be included in windows mobile applications.
Now the overwhelming advice here seems to be use an embedded database, though I now do have use cases and it appears that I will need to have document synchronization as well as relational data. With this in mind service layer interaction seems inevitable. So my question is how would I share common domain objects and interfaces between the layers?
"Document synchronization" - does that mean bidirectional? Or cumulative write-only? I can think of mobile architectures that would mainly collect and submit transactions for a shared document - if that's your requirement, then we should discuss offline - it's a long (and interesting) conversation.
Owen you can share code from Compact Framework -> Desktop, it's only Desktop -> Compact Framework that has compatability issues if you use certain objects that are not supported by the CF.
While a desktop lib doesn't work on CF a CF lib WILL work on the desktop, you can also run CF.exes on the desktop!
Just create a CF library as the project that defines your base objects / interfaces etc.
This book sshould e essential reading for all Windows Mobile developers: http://www.microsoft.com/learning/en/us/books/10294.aspx
For developing windows mobile applications you must have the basic tools like silverlight, visual studio, windows phone emulator and sqlite as your database storage.