What is OData

The Open Data Protocol (OData) is a Web protocol for querying and updating data that provides a way to unlock your data and free it from silos that exist in applications today. OData does this by applying and building upon Web technologies such as HTTP, Atom Publishing Protocol (AtomPub) and JSON to provide access to information from a variety of applications, services, and stores. The protocol emerged from experiences implementing AtomPub clients and servers in a variety of products over the past several years. OData is used to expose and access information from a variety of sources including, but not limited to, relational databases, file systems, content management systems and traditional Web sites.

OData is consistent with the way the Web works - it makes a deep commitment to URIs for resource identification and commits to an HTTP-based, uniform interface for interacting with those resources (just like the Web). This commitment to core Web principles allows OData to enable a new level of data integration and interoperability across a broad range of clients, servers, services, and tools.

copied from http://odata.org

Teiid Support for OData

When a user successfully deploys a VDB into a Teiid Server, the OData protocol support is implicitly provided by the Teiid server without any further configuration. OData support is currently not available in the Teiid Embedded profile. Teiid makes use of JBoss AS and its already configured RestEasy and OData4J libraries to provide Rest based access to the VDB. The access would be similar to accessing to any web resources deployed on JBoss AS. OData support is implemented and deployed through a single WAR file across the Teiid system. A user can access this WAR file at <jboss-as>/modules/org/jboss/teiid/deployments/odata-8.8.0.Final.war.

http://localhost:8080/odata/northwind.1/NW.customers

SELECT * FROM NW.customers

When you issue the above query are you seeing a message similar to below?
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
<code>NotFoundException</code>
<message lang="en-US">EdmEntitySet NW.customer is not found</message>
</error>

http://localhost:8080/odata/northwind.1/NW.customers?$skiptoken=256

http://localhost:8080/odata/northwind.1/NW.customers?$filter=name eq 'bob'

SELECT * FROM NW.customers where name = 'bob'

http://localhost:8080/odata/northwind.1/NW.customers(1234)/NW.orders?$filter=orderdate gt datetime'2012-12-31T21:23:38Z'

SELECT * FROM NW.orders o join NW.customers c join o.customer_id = c.id where c.id=1234 and o.orderdate > {ts '2012-12-31 21:23:38'}

POST /service.svc/Customers HTTP/1.1
Host: host
Content-Type: application/atom+xml
Accept: application/atom+xml
Content-Length: nnn
<?xml version="1.0" encoding="utf-8"?>
<entry xml:base="http://host/service.svc/"
xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices"
xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"
xmlns="http://www.w3.org/2005/Atom">
    <id>http://host/service.svc/Customers('ASDFG')</id>
    <title type="text" />
    <updated>2008-12-07T8:00:00Z</updated>
    <author>
        <name />
    </author>
    <link rel="http://schemas.microsoft.com/ado/2007/08/dataservices/related/Orders" href="Orders(1)" />
    <link rel="http://schemas.microsoft.com/ado/2007/08/dataservices/related/Orders" href="Orders(2)" />
    <content type="application/xml">
        <m:properties>
            <d:CustomerID>ASDFG</d:CustomerID>
            <d:CompanyName>Contoso Widgets</d:CompanyName>
            <d:Address>
                <d:Street>58 Contoso St</d:Street>
                <d:City>Seattle</d:City>
            </d:Address>
        </m:properties>
    </content>
</entry>

PUT /service.svc/Customers('ALFKI') HTTP/1.1
Host: host
Content-Type: application/atom+xml
Accept: application/atom+xml
Content-Length: nnn
DataServiceVersion: 1.0
MaxDataServiceVersion: 3.0
Prefer: return-content
<?xml version="1.0" encoding="utf-8"?>
<entry xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom">
    <content type="application/xml">
    <m:properties>
        <d:CustomerID>ALFKI</d:CustomerID>
        <d:CompanyName>Updated Company Name</d:CompanyName>
        <d:Address>
        <d:Street>Updated Street</d:Street>
        </d:Address>
    </m:properties>
    </content>
</entry>

DELETE /service.svc/Customers('ALFKI') HTTP/1.1
Host: host
Content-Type: application/atom+xml
Accept: application/atom+xml
Content-Length: nnn
DataServiceVersion: 1.0

    <context-param>
        <param-name>proxy-base-uri</param-name>
        <param-value>${system-property-name}</param-value>
    </context-param>  

Client Tools for Access

OData access is really where the user comes in, depending upon your programming model and needs there are various ways you write your access layer into OData. The following are some suggestions:

• Your Browser: The OData Explorer is an online tool for browsing an OData data service.

• Microsoft .NET Framework 3.51: the WCF Data Services framework is available as a separate download for .NET 3.x.

• Microsoft .NET Framework 4.0: the WCF Data Services framework built into .NET 4.0 (in release candidate as of this writing).

• Silverlight 3: the Data Services client library for Silverlight is available for download.

• Java: the Restlet 2.0 library for Java (including Java on your Android phone) supports the OData protocol.

• Java: Use a library like OData4J for Java based access, or any Rest based framework

• JavaScript: the XMLHttpRequest object is standard in modern browsers or you can use jQuery, which comes out of the box with .NET 4.0 or is available for download.

• PHP: the Toolkit for PHPprovides OData support for PHP clients.

• AJAX: if you're using AJAX for ASP.NET, Microsoft provides the ASP.NET Ajax Library for getting to OData.

• Excel 2010 PowerPivot: PowerPivot comes with OData support built right in.

• Windows Desktop: LINQPad is a wonderful tool for building OData queries interactively.

• Shell Scripts: use CURL tool

How Teiid exposes schema for OData

OData defines its schema using Conceptual Schema Definition Language (CSDL). Every VDB, that is deployed in an ACTIVE state in Teiid server exposes its metadata in CSDL format. For example if you want retrieve metadata for your vdb northwind, you need to issue a query like

http://localhost:8080/odata/northwind/$metadata

Since OData schema model is not a relational schema model, Teiid uses the following semantics to map its relational schema model to OData schema model.

Teiid by design does not define any "embedded" ComplexType in the EntityType.