Digital Directions: Tiers Without Fears
Complex systems, such as digital publishing platforms, are composed of a number of components that work together. Software architects often think of these components as being arranged in layers, or "tiers," like a layer cake.
While there is a lack of consensus as to how these tiers should be defined, there is strong convergence around one particular flavor of this layer cake. Most system architects think in terms of a three-tier architecture:
- Presentation layer. The top of the cake is the user interface. A user could be a member of the editorial staff, marketing staff, production or design team—as well as customers, or end users. Most systems use presentation layers based on the Web, in which end users access the system with Web browsers.
- Data layer. The bottom layer is the data layer, where all of the data assets reside. These data assets may include digital media assets maintained in content repositories—e.g., image libraries residing in VirtuSales' BiblioDAM, fielded data residing in a relational database (price data in SQLServer), XML content managed by a native XML database (MarkLogic Server), and metadata—that may be found in any of the above.
- Business logic layer. The middle layer is devoted to the management of business logic. Business logic includes the application of business rules, such as restricting access of certain functions to certain users. Business logic also includes business process workflow, such as a publishing workflow. The middle layer also manages how the top layer and the bottom layer connect.
Some common characteristics of well-constructed three-tier systems:
Layer modularity. Modularity enables the replacement of one layer without replacing the whole cake. This allows systems to evolve over time.
Well-documented interfaces. The interfaces between layers—how the layers communicate with adjacent layers—should be clearly documented and easily understood by developers. If interfaces are well-documented, then a layer can be replaced, with the new layer connecting to the other layers the same way the old one did.
Standards-based technologies. All three layers should adhere to industry standards, rather than a proprietary approach. For example, it is far preferable to manage fielded data in an SQL-based database as opposed to a proprietary format.
Why It's Important
How useful is this to anyone outside of a technical development team? Plenty:
Understanding current state. Many publishing organizations already have a plethora of digital assets, applications and services that they have picked up over the course of the last decade or two. The three-tier model is a significantly useful tool in mapping and understanding current systems and assets.
Defining the publishing platform's evolutionary path. Digital platforms should follow an evolutionary path, in which modules are implemented and replaced over time. This is far preferable to the "big bang" model of system deployment in which a big, expensive, monolithic system is rolled out overnight. The three-tier model provides a structure for planning such an evolutionary path.
Vendor evaluation. Many organizations have recognized that a digital publishing platform will involve several technologies and services providers. The three-tier model is useful in evaluating vendors, by mapping their offerings against the layers of the cake. Note that a vendor may well provide multiple layers of the cake. However, if the vendor does not adhere to the practice of modularity of layers—if you can't replace one layer at a time—then your ability to evolve your platform is significantly compromised: You are going to be stuck with that one vendor.
The three-tier architecture not only is useful for systems architects; it also is useful for business planners. Its use as a business-planning tool has an additional benefit: It allows the technical and nontechnical teams to speak the same language. Digital transformation of publishing organizations is greatly facilitated by the use of common terms and concepts across departmental boundaries.
Andrew Brenneman is founder of Finitiv (Finitiv.com), a consulting and services organization that develops and executes transformative digital strategy for publishers and other content organizations.