Toward a Reusable Content Repository
July 22, 2013
There are a plethora of web-based content management systems and website publishing systems in the world. Almost all of them are what you might call "full stack solutions," meaning that they try to cover everything you need to cook up a full publishing system, from content editing to theming. Wordpress is the most obvious example, but there are hundreds of such systems varying in complexity, cost, and implementation platform.
So many of the available products are full stack solutions that the market seems to have forgotten the possibility of anything else. What would it look like if you could assemble a CMS from ready-made components? What might those components be, and how would they interoperate?
Every web CMS that I have seen can be divided into three major components. They are:
- Content Repository
- Publishing Tools
- Site Presentation
Each of those major components could further be described with a feature set that might be implemented with sub-components. The Site Presentation component might provide Themes or Sidebar Modules. The Publishing Tools might be as simple as a bare textarea, or might include WYSIWYG with spell checking and media embedding. The Content Repository is, almost universally, a relational database.
The Content Repository, I believe, is the reason that so many systems ship as full-stack solutions. There is no reusable Content Repository component that meets the general needs of content management systems. Without that central component, implementors are forced to bind both their Publishing Tools and their Site Presentation systems tightly to their own custom repository.
I would suggest the following feature set for a reusable Content Repository.
- Flexible and extensible information architecture, with a sensible default that will work out of the box for most users.
- Web API for content storage and retrieval (not just a native language API).
- Fielded search and full-text search over stored objects.
- Optional version history for content objects.
- Optional explicit relationships between content objects.
- Pluggable backends, allowing for implementations at different scales.
Most internal repositories are quite weak in this feature set. For example, very few embedded repositories implement full-text search. Of those who do implement it, the implementation is often naive (SQL LIKE % queries), leading to poor performance and poor scalability.
Most embedded repositories implement only a native-language API, not a web API, which prevents access to the content unless you also have access to the code (some see this as a feature rather than a bug).
Relational databases are notoriously bad at flexible information architecture, so it has taken a lot of time and effort for content management systems to add flexibility. Tools like Drupal's Content Construction Kit and Wordpress Custom Post Types are getting there, but without a common base architecture to build on, every implementation is custom and incompatible with the next.
Regardless of the features listed above, there are two key requisites that a reusable Content Repository must fulfill:
- A published (and preferably simple) protocol for accessing its features.
- A common base information architecture for content objects.
A Content Repository with these features would serve as a good backing store for Publishing Tools and Site Presentation systems alike, and would be agnostic to both. Any tool that understood the information architecture and protocol used by the Content Repository could build on it easily. Tools could ship with an embedded Content Repository, or connect to an external one that might be hosted on a provider's servers. Most importantly, your Site Presentation would no longer need to be bundled with your Publishing Tools.
Content Repository Protocol
There are very few contenders for content repository protocols. I only know of two that might be reasonable to build on: AtomPub, and CMIS. To my mind, neither of these is a solution, but examining them might help us develop a solution.
CMIS, despite its name, is geared more toward Document Management than Content Management (IMHO).
CMIS is far from being simple, and it makes some assumptions about information architecture that make it awkward to use in many cases. For example, it assumes a distinction between documents and folders, and assumes that there is a single folder hierarchy for all content. This is a restrictive and unnecessary constraint that does not fit all use cases.
It also requires repositories to implement a SQL-like query language, forcing them to map content to a relational model even when it is not stored that way. This makes implementations expensive, and makes certain kinds of queries difficult to craft.
AtomPub, on the other hand, is simple and well-crafted, but defines only a fraction of the feature set we would want in a protocol. For example, it has no defined search protocol at all. Some implementations extend the protocol to mimic Google's GData search protocol, but it is not a standard, and Google is no longer using it.
Implementers of a reusable Content Repository will have to face the challenge of a new protocol for accessing it. That's a pretty high barrier.
Common Information Architecture
When I talk about a common information architecture, I am referring to standardizing the shape of content objects in terms of the semantics of its field structure. We need a commonly understood set of metadata, so that tools can share content in a sensible way. Some metadata will be required by Publishing Tools, other metadata will be useful to Site Presentation systems, and some will be needed internally by the Content Repository itself.
Atom and RSS are format standards, but each also defines a base information architecture, and they are mostly compatible with each other. Neither is sufficient for a full Content Repository, but any information architecture incompatible with these formats is a non-starter.
The IPTC has done a huge amount of work in developing interoperability standards for the news industry, which is all about content management. Their G2 News Architecture is documented implicitly in the specifications for their XML exchange formats, and in their rNews metadata format for HTML. I think the G2 News Architecture is a great start on a common information architecture, but a reusable Content Repository would need to define a simpler useful subset of it if it wanted to gain wide adoption.
Conclusion: A Hole in the Market? or No Market?
There are no real conclusions to draw from this, only questions to ask. Namely, is there an under-served market for a reusable Content Repository out there? Perhaps everyone is content with their vertically integrated solutions, and no one is interested in mixing and matching their presentation layer with different publishing tools.
I suspect, however, that the market for a reusable Content Repository will emerge as a result of the proliferation of Internet accessible devices. As people want access to their CMS across desktops, tablets, smart phones, and other devices, the utility of separating the presentation from the repository will become obvious.
Of course, the only way to know is to put in the hard work to build it, and see who bites.