Databases Reference
In-Depth Information
We'll see some examples of these clauses later in the chapter. Where they occur, we'll
describe in more detail how they work.
Now that we've seen how we can describe and query a graph using Cypher, we can look
at some examples of graph modeling.
A Comparison of Relational and Graph Modeling
To introduce graph modeling, we're going to look at how we model a domain using both
relational- and graph-based techniques. Most developers and data professionals are
familiar with RDBMS systems and the associated data modeling techniques; as a result,
the comparison will highlight a few similarities, and many differences. In particular,
we'll see how easy it is to move from a conceptual graph model to a physical graph
model, and how little the graph model distorts what we're trying to represent versus the
relational model.
To facilitate this comparison, we'll examine a simple data center management domain.
In this domain, several data centers support many applications on behalf of many cus‐
tomers using different pieces of infrastructure, from virtual machines to physical load
balancers. An example of this domain is shown in
Figure 3-2
.
In
Figure 3-2
we see a somewhat simplified view of several applications and the data
center infrastructure necessary to support them. The applications, represented by nodes
App 1
,
App 2
, and
App 3
, depend on a cluster of databases labeled
Database Server 1,
2, 3
. While users logically depend on the availability of an application and its data,
there is additional physical infrastructure between the users and the application; this
infrastructure includes virtual machines (
Virtual Machine 10, 11, 20, 30, 31
), real
servers (
Server 1, 2, 3
), racks for the servers (
Rack 1, 2
), and load balancers (
Load
Balancer 1, 2
), which front the apps. In between each of the components there are,
of course, many networking elements: cables, switches, patch panels, NICs, power sup‐
plies, air conditioning, and so on—all of which can fail at inconvenient times. To com‐
plete the picture we have a straw-man single user of application 3, represented by
User 3
.
