MSDN Magazine - July 2008 - (Page 59)

data solution around SSDS. I will begin by mapping out the data model that is employed by SSDS. Then I will dive into the development details by showing you how I built the simple online classified ads system, shown in Figure 1, using SSDS. SSDS Data Model SSDS provides a flexible entity-based data model. This model has three main elements—authority, container, and entity—referred to as the ACE concepts (see Figure 2). An SSDS authority can be related to a database in the relational world. When you provision an authority, SSDS will create Figure 1 Sample Classifieds App Hosted by SSDS a DNS name for you to access the authority. For instance, if you provision an authority called ssdsdemo, you will Kind is used to categorize similar entities together. There access it at the following URI: is no schema attached to the entity, so having entities of ssdsdemo.data.beta.mssds.com the same Kind does not guarantee the same structure, An authority is also the unit of geo-location, meaning and Version is used to identify the current version of the that the created DNS name will map to a specific Microentity. This value gets updated on each operation. soft datacenter where your data is hosted. If you create Flexible properties are where the developer stores the two authorities—americasdemo.data.beta.mssds.com application data. Flexible properties support simple types: and europedemo.data.beta.mssds.com—each one will string, decimal, bool, datetime, and binary. Each flexible be associated with a different datacenter that is located property is indexed up to the first 256 bytes. closest to your users. Figure 2 An authority contains a collection of containers—a conBuilding a Classified Ads System Basic SSDS tainer is similar to a table in a relational database. The key To demonstrate the features of SSDS and to give an Components difference is that you attach a schema to a database table overview of the development experience, I will walk you to make all rows in the table homogeneous. A container in SSDS through the implementation of a sample online classifieds system, does not require a schema, which allows you to store heteroge- Contoso Classifieds. The sample comprises two separate applicaneous entities in one convenient location. It is simply a collection tions: a Windows® Forms application to administer the system and of entities. In the current release of SSDS, all queries are scoped to an ASP.NET application—the main Contoso Classifieds site—that a single container. users would visit. The application accesses SSDS via a SOAP interface One other important point to make here is that each container in the Windows Forms application and through the Representational is placed on a different node in the SSDS cluster. In SQL Server, to State Transfer (REST) interface within the ASP.NET application. gain additional performance, you would place different tables on When you sign up for a SSDS account, you will receive a user separate spindles to maximize your read/write capabilities. This name and password. From there it is up to you to begin building is similar in SSDS except that instead each container will be on a your authorities, containers, and entities. For Contoso Classifieds, I separate machine. Additional performance gains can be realized set up the authority as contosoclassifieds and the service URI endby partitioning your data across multiple containers and multi- point in the beta release of SSDS is data.data.beta.mssds.com. threading your requests since your reads and writes won’t be conThe contosoclassifieds authority includes two containers: Catestrained by a single machine. gories and Cities. Categories will contain the entities related to the A final note about containers is that while each container is Listing categories. Cities will contain an entity for each city defined placed on a separate node in the SSDS cluster, the data is also rep- in the system. Those entities will simply be pointers to city-specific licated on several other nodes for disaster recovery purposes. If the authorities. Each city-specific authority will have a container per machine your container is on fails, one of the backup replicas are listing category (see Figure 3). promoted automatically to ensure your applications doesn’t observe any data or performance loss. An entity can be compared to a row in a table in a relational database. An entity is simply a property bag of name/value pairs. These name/value pairs are grouped into two categories: distinguished system properties and flexible properties. Distinguished system properties are common to all entities and include ID, Kind, and Version. ID uniquely identifies the entity. IDs must be unique within the container it exists in, but different containers can have entities with the same ID. Figure 3 Contoso Classifieds Elements msdnmagazine.com July 2008 59 http://msdnmagazine.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - July 2008

MSDN Magazine - July 2008 Contents Toolbox CLR Inside Out Flex Your Data Data Points Advanced Basics Office Space Cutting Edge Data Services ADO.NET Data and WPF Transactions WCF P2P Test Run Security Briefs Foundations .NET Matters {End Bracket}

MSDN Magazine - July 2008

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