OData, the Open Data Protocol, is described at odata.org:

The Open Data Protocol (OData) is a web protocol for querying and updating data. OData applies 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 other day, Pablo Castro wrote an excellent post explaining how developers can implement aspects of the modular OData spec, and outlining some benefits that accrue from each. One of the aspects is query, and Pablo gives this example:

http://ogdi.cloudapp.net/v1/dc/BankLocations?$filter=zipcode eq 20007

One benefit for exposing query to developers, Pablo says, is:

Developers using the Data Services client for .NET would be able to use LINQ against your service, at least for the operators that map to the query options you implemented.

I’d like to suggest that there’s a huge benefit for users as well. Consider Pablo’s example, based on some Washington, DC datasets published using the Open Government Data Initiative toolkit. Let’s look at one of those datasets, BankLocations, through the lens of Excel 2010′s PowerPivot.

PowerPivot adds heavy-duty business analytics to Excel in ways I’m not really qualified to discuss, but for my purposes here that’s beside the point. I’m just using it to show what it can be like, from a user’s perspective, to point an OData-aware client, which could be any desktop or web application, at an OData source, which could be provided by any backend service.

In this case, I pointed PowerPivot at the following URL:


I previewed the Atom feed, selected a subset of the columns, and imported them into a pivot table. I used slicers to help visualize the zipcodes associated with each bank. And I wound up with a view which reports that there are three branches of WashingtonFirst Bank in DC, at three addresses, in two zipcodes.

If I were to name this worksheet, I’d call it WashingonFirst Bank branches in DC. But it has another kind of name, one that’s independent of the user who makes such a view, and of the application used to make it. Here is that other name:

http://ogdi.cloudapp.net/v1/dc/BankLocations?$filter=name eq ‘WashingtonFirst Bank’

If you and I want to have a conversation about banks in Washington, DC, and if we agree that this dataset is an authoritative list of them, then we — and anyone else who cares about this stuff — can converse using a language in which phrases like ‘WashingtonFirst Bank branches in DC’ or ‘banks in zipcode 20007′ are well defined.

If we incorporate this kind of fully articulated web namespace into public online discourse, then others can engage with it too. Suppose, to take just one small example, I find what I think is an error in the dataset. Maybe I think one of the branch addresses is wrong. Or maybe I want to associate some extra information with the address. Today, the way things usually work, I’d visit the source website and look for some kind of feedback mechanism. If there is one, and if I’m willing to provide my feedback in a form it will accept, and if my feedback is accepted, then my effort to engage with that dataset will be successful. But that’s a lot of ifs.

When public datasets provide fully articulated web namespaces, though, things can happen in a more loosely coupled way. I can post my feedback anywhere — for example, right here on this blog. If I have something to say about the WashingtonFirst branch at 1500 K Street, NW, I can refer to it using an URL: 1500 K Street, NW.

That URL is, in effect, a trackback that points to one record in the dataset.1 The service that hosts the dataset could scan the web for these inbound links and, if desired, reflect them back to its users. Or any other service could do the same. Discourse about the dataset can grow online in a decentralized way. The publisher need not explicitly support, maintain, or be liable for that discourse. But it can be discovered and aggregated by any interested party.

The open data movement, in government and elsewhere, aims to help people engage with and participate in processes represented by the data. When you publish data in a fully articulated way, you build a framework for engagement, a trellis for participation. This is a huge opportunity, and it’s what most excites me about OData.

1 PowerPivot doesn’t currently expose that URL, but it could, and so could any other OData-aware application.