Welcome!

Microsoft Cloud Authors: Janakiram MSV, Yeshim Deniz, David H Deans, Andreas Grabner, Stackify Blog

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

An Exploration of the ObjectSpaces Framework

Accessing data through application business domain objects

With the release of the alpha bits of ADO.NET 2.0 and Visual Studio 2005, Microsoft is experimenting with a framework that provides .NET programmers with a new way to access and work with relational data. Traditionally, passing and persisting data to the data storage layer has been very data-centric, as it consisted of thinking of data in terms of tables, rows, and columns. This conflicts with the object-centric paradigm of the business logic layer where data is defined in terms of objects and properties. As a result, a lot of custom code is written and maintained to couple the data-centric database storage layer to the object-centric business layer. ObjectSpaces enables you to work with the data through the business- level objects that make up the application domain. The classes that make up the ObjectSpaces architecture allow you to abstract out the complexity of the data-centric syntax of the storage medium from the object-oriented developer. This article introduces the ObjectSpaces framework and demonstrates the fundamentals of implementing ObjectSpaces in a .NET application.

ObjectSpaces: An Introduction
A valid question you may be asking is, "What is the ObjectSpaces framework and what problem is it trying to solve?" Quite simply, ObjectSpaces is technology built on top of ADO.NET, to provide data-access support. With the addition of ObjectSpaces, ADO.NET supports three main forms of data access technology. The most obvious and utilized data-access technology is the DataSet/DataReader. The strength of DataSets and DataReaders are that they incorporate a relational model common to most relational back-end databases and fully expose the database functionality. They also provide the highest performance compared to the other data-access technologies.

Another data-access technology is SQLXML. The strength of SQLXML is its ability to decouple the data from the database schema. When data needs to be exposed as XML structures, such as Web services and B2B applications, SQLXML is generally the data access of choice. It also provides the ability to map the same data to different schemas for content publishing to various vertical industry standards.

ObjectSpaces is similar to SQLXML in that it decouples the data structure from the database schema. The difference is that ObjectSpaces exposes the schema based on the business-level objects in the application as opposed to XML structures. ObjectSpaces is the way to go if the application has a strong business object layer and the data needs exposure through an object model instead of a relational model.

As you can see, each of these data access technologies exposes a different set of functionalities to solve various problems. It is important that you understand the strengths and weaknesses of each of the data-access technologies. Armed with this knowledge, you will make better decisions on how to design your data-access strategies.

ObjectSpaces is an object-relational mapping (O/RM) framework embedded in ADO.NET. Although O/RM technologies are not new and several third parties offer .NET add-ins, Microsoft is including ObjectSpaces as part of the .NET Framework. O/RM essentially couples the application's object model with the underlying data storage engine. To accomplish this, the O/RM engine uses a mapping file to make the necessary translations.

The ObjectSpaces engine uses an XML mapping file that translates from an object query/update call into the SQL query/update call. By moving the mapping schema into a separate file, objects can be persisted and retrieved from the data storage without writing provider-specific code. Object-oriented programmers can work with the object data using familiar object-oriented syntax.

Mapping Object Relationships
For O/RM to work, the O/RM engine needs a mapping file that defines the schema of the data base, the schema of the objects, and how the schema is mapped between the two. To demonstrate the creation of a mapping file we will create a simple object type – product – and map it to the products table in the Northwind database. Listing 1 (the listings are online at www.sys-con.com/dotnet/sourcec.cfm) defines the product class. Listing 2 shows the XML mapping file used to define the mapping between the product class and the products table.

The database definition schema is defined within the <m:Data Source> </m:DataSource > tags. The object schema is defined within the <m:DataTarget> </m:DataTarget> tags. Notice that object schema tags contain the prefix "osd:" as a namespace alias. (One little caveat of which to be careful: when exposing your data through properties of the class instead of public fields, you need to specify the property as an alias attribute of the field <osd:member> node.)

The mapping schema is defined within the <m:Mappings> </m:Mappings> tags. As you probably realized, creating even the simplest of mapping files is not a trivial exercise and when creating one by hand, using note pad is not practical. Fortunately, Microsoft will provide a mapping utility that will greatly simplify this process. Figure 1 shows the current incarnation of the mapping utility, which allows you to drag and drop data tables and classes onto the design surface and visually create the mappings.

ObjectSpaces supports complex mappings such as one-one, one-many, and many-many. As an example of a one-many mapping, a Supplier class is defined that is related to the Product class. To link the parent Supplier class with the child Product class, a property of a type that implements the IList interface is defined. The child class links back to the parent class through a property of type parent in the child class.

Listing 3 contains the definitions of the Supplier and Product classes. To support this relationship, the mapping file is updated to include an <osd:ObjectRela tionship> node that includes a schema defining the relationship between the two objects. The updated schema also reflects the definition relating the Supplier table and the Products table from the Northwind Database. Listing 4 shows the updated nodes added to the mapping files.

Retrieving Objects
To use ObjectSpaces, the application needs to reference the System.Data.ObjectSpaces and System.Data.SqlXml assemblies. The ObjectSpace class acts as the broker between the database model and the object model. An ObjectSet is then instantiated through the GetObjectSet method of an ObjectSpace. The ObjectSet represents a collection of objects returned from the GetObjectSet method. The GetObjectSet method takes a parameter of type string, which defines the query used to retrieve the object data (more about this later). Listing 5 demonstrates retrieving and populating a collection of Product objects and displaying their ProductName properties in a list. Figure 2 shows the resulting list. The ObjectSet provides functionality similar to the DataSet. For example, it enables data binding to Windows Forms controls and tracking values for optimistic concurrency checking.

Along with the features provided with the ObjectSet, the results of an object query can be returned through an ObjectReader. The ObjectReader is analogous to the DataReader. It provides a forward-only, low-overhead stream of objects. It is useful when you need to read the data out of the Objects but do not need the overhead of persisting the entire object model. Listing 6 demonstrates retrieving the ProductName property of the Product objects and loading them into a list box using an ObjectReader.

Spans and Delay Loading
Spans and delay loading provide more control over the way the object model is loaded. A span identifies the related objects that are returned along with the objects retrieved by the query. For example, when retrieving the Supplier objects, you can use a span to retrieve the associated products. Listing 7 uses a span to retrieve both the Suppliers and their related Products. Each Supplier's CompanyName property is loaded into a TreeView control as a parent node and the associated Products' ProductNames are loaded as the corresponding child nodes. (Remember that the relationship between these objects must also be modeled in the mapping file.) Figure 3 shows the resulting TreeView display.

For performance reasons, there are times when you do not want to load the related objects immediately. ObjectSpaces supports on-demand loading of the related objects using delayed loading. To implement delayed loading, ObjectSpaces provides two classes that provide a wrapper for the classes in the relationship. The ObjectList class provides delayed loading for a one-many relationship and the ObjectHolder class provides delayed loading for a one-one relationship. Listing 8 shows the Supplier class altered to take advantage of delayed loading. Notice the Products field and the Products property are of type ObjectList. Listing 9 shows the loading of a second list box depending on the value selected in the first list box by delayed loading. Figure 4 shows the resulting list boxes.

Querying Objects with OPath
One of the most interesting aspects of the ObjectSpaces framework is the development of an object query language. OPath allows object-oriented programmers the ability to use familiar object-oriented syntax to query the object model. It includes a rich feature set of literals, operators, predicates, and functions. Using OPath, programmers can construct complex queries using the syntax with which they are most comfortable working, while giving the ObjectSpaces engine the arduous task of converting it to the database querying syntax. In the previous examples, an empty string was passed in with the instantiation of the ObjectQuery object. This results in pulling back the entire object set. Listing 10 demonstrates restricting the result set using an OPath query. Listing 11 contains the ensuing SQL generated by the ObjectSpaces engine. Although I can only scratch the surface of the OPath query language in this article, look for a future article devoted to this topic as the language matures.

Conclusion
With the ObjectSpaces framework, Microsoft is providing an intriguing technology to .NET programmers. The classes that make up the ObjectSpaces architecture provide the ability to abstract out the complexity of the data centric syntax of the storage medium. Object-oriented developers can work with the data using familiar OOP syntax and the object centric model of the business layer. ObjectSpaces is evolving to offer a rich feature set including object/relational mapping, delayed loading, data binding, transactional support, and an optimistic concurrency model.

The possibilities of this technology are fascinating and I hope that this article gave you a feel for the direction in which Microsoft is moving with the ObjectSpaces framework. Unfortunately, we will have to wait a little longer for the full release of this framework. Microsoft has recently announced that the release of the ObjectSpaces framework is now aligned with the WinFS/Longhorn release timeframe. On the upside, this indicates that ObjectSpaces is an integral part of Microsoft's future and will only get better and more mature over time.

More Stories By Dan Clark

Dan is a Microsoft Certified Trainer, Microsoft Certified Solution Developer, and a Microsoft Certified Database Administrator. For the past seven years he has been developing applications and training others how to develop applications using Microsoft technologies. Dan has been developing and training Microsoft's .NET technologies since the early betas. He has recently authored the book "An Introduction to Object-Oriented Programming with Visual Basic .NET," published by Apress.

Comments (4) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Zeeshan Shakeel 08/13/07 09:05:27 AM EDT

interesting article, fantastic effort, welldone Dan
take care

Santosh Benjamin 11/22/04 09:51:38 AM EST

Dan,
Sorry i missed that part of the conclusion. I agree that its good for the maturity of the framework, but i think they will also lose some momentum in this space to open source technologies such as NHibernate etc. Anyway, all we can do is wait and see. Perhaps it will turn out to be a killer app!!

Dan Clark 07/07/04 02:34:03 PM EDT

Santosh - You are correct that ObjectSpaces has been stripped from ADO 2.0, as I mentioned in the conclusion. The good news is that it will resurface in the near future.

Santosh Benjamin 07/07/04 10:29:08 AM EDT

Interesting article. As far as i know though, ObjectSpaces is not in ADO.NET 2.0 and has been moved to the Longhorn/Orcas timeframe. See the following articles
http://blogs.msdn.com/aconrad/archive/2004/06/01/146315.aspx
and
http://weblogs.asp.net/aaguiar/archive/2004/05/26/141931.aspx

@ThingsExpo Stories
SYS-CON Events announced today that Synametrics Technologies will exhibit at SYS-CON's 22nd International Cloud Expo®, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Synametrics Technologies is a privately held company based in Plainsboro, New Jersey that has been providing solutions for the developer community since 1997. Based on the success of its initial product offerings such as WinSQL, Xeams, SynaMan and Syncrify, Synametrics continues to create and hone inn...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...
Recently, WebRTC has a lot of eyes from market. The use cases of WebRTC are expanding - video chat, online education, online health care etc. Not only for human-to-human communication, but also IoT use cases such as machine to human use cases can be seen recently. One of the typical use-case is remote camera monitoring. With WebRTC, people can have interoperability and flexibility for deploying monitoring service. However, the benefit of WebRTC for IoT is not only its convenience and interopera...
The 22nd International Cloud Expo | 1st DXWorld Expo has announced that its Call for Papers is open. Cloud Expo | DXWorld Expo, to be held June 5-7, 2018, at the Javits Center in New York, NY, brings together Cloud Computing, Digital Transformation, Big Data, Internet of Things, DevOps, Machine Learning and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding busin...
Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
No hype cycles or predictions of a gazillion things here. IoT is here. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, an Associate Partner of Analytics, IoT & Cybersecurity at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He also discussed the evaluation of communication standards and IoT messaging protocols, data...
Product connectivity goes hand and hand these days with increased use of personal data. New IoT devices are becoming more personalized than ever before. In his session at 22nd Cloud Expo | DXWorld Expo, Nicolas Fierro, CEO of MIMIR Blockchain Solutions, will discuss how in order to protect your data and privacy, IoT applications need to embrace Blockchain technology for a new level of product security never before seen - or needed.
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
Cloud Expo | DXWorld Expo have announced the conference tracks for Cloud Expo 2018. Cloud Expo will be held June 5-7, 2018, at the Javits Center in New York City, and November 6-8, 2018, at the Santa Clara Convention Center, Santa Clara, CA. Digital Transformation (DX) is a major focus with the introduction of DX Expo within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive ov...
"Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, discussed how they built...
Digital Transformation (DX) is not a "one-size-fits all" strategy. Each organization needs to develop its own unique, long-term DX plan. It must do so by realizing that we now live in a data-driven age, and that technologies such as Cloud Computing, Big Data, the IoT, Cognitive Computing, and Blockchain are only tools. In her general session at 21st Cloud Expo, Rebecca Wanta explained how the strategy must focus on DX and include a commitment from top management to create great IT jobs, monitor ...
"Digital transformation - what we knew about it in the past has been redefined. Automation is going to play such a huge role in that because the culture, the technology, and the business operations are being shifted now," stated Brian Boeggeman, VP of Alliances & Partnerships at Ayehu, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...