Open Data Protocol by Example

The purpose of the Open Data protocol[i] (hereafter referred to as OData) is to provide a REST-based protocol for CRUD-style operations (Create, Read, Update and Read) against resources exposed as data services. A “data service” is an endpoint where there is data exposed from one or more “collections” each with zero or more “entries”, which consist of typed named-value pairs. OData is published by Microsoft under the Open Specification Promise so that anyone that wants to can build servers, clients or tools without royalties or restrictions.

Exposing data-based APIs is not something new. The ODBC (Open DataBase Connectivity) API is a cross-platform set of C language functions with data source provider implementations for data sources as wide ranging as SQL Server and Oracle to comma-separated values and Excel files. If you’re a Windows programmer, you may be familiar with OLEDB or ADO.NET, which are COM-based and.NET-based APIs respectively for doing the same thing. And if you’re a Java programmer, you’ll have heard of JDBC. All of these APIs are for doing CRUD across any number of data sources.

Since the world has chosen to keep a large percentage of its data in structured format, whether it’s on a mainframe, a mini or a PC, we have always needed standardized APIs for dealing with data in that format. If the data is relational, the Structured Query Language (SQL) provides a set of operations for querying data as well as updating it, but not all data is relational. Even data this is relational isn’t often exposed for use in processing SQL statements over intranets, let alone internets. The structured data of the world is the crown jewels of our businesses, so as technology moves forward, so must data access technologies. OData is the web-based equivalent of ODBC, OLEDB, ADO.NET and JDBC. And while it’s relatively new, it’s mature enough to be implemented by IBM’s WebSphere[ii], be the protocol of choice for the Open Government Data Initiative[iii] and is supported by Microsoft’s own SharePoint 2010 and WCF Data Services framework[iv]. In addition, it can be consumed by Excel’s PowerPivot, plain vanilla JavaScript and Microsoft’s own Visual Studio development tool.

In a web-based world, OData is the data access API you need to know.

Atom

OData is built as an application of a set of internet standards, most especially the Atom Publishing Protocol (aka “AtomPub” specified as RFC 5023), which itself is built on top of the Atom Syndication Format (aka “Atom” specified as RFC 4287). Because of this layering, Atom is the XML format in which OData data is published. AtomPub is the protocol to provide not only getting Atom data, but also creating it, updating it and deleting it, all of which OData relies upon. Finally, OData provides a set of features on top of Atom and AtomPub to make the data query and manipulation richer. So, before we get to AtomPub or OData, let’s look at the base: Atom.

Read more: MSDN Data Development Center

Posted via email from jasper22's posterous