JISC – Open Book Project

releasing open data for illuminated manuscript collection records and research…

It’s Obvious #2

Part 2 – What’s “Middleware”

I like the beginning of the Wikpedia article for Middleware (I’m dropping the Middleware quotes now in the name of efficiency, too many keystrokes…). It spends most of the first paragraph saying what Middleware is not. But I’m not here to bore you with definitions, lets keep it simple…

Figure 1

Basically, Middleware does something, to something, to produce something. My other jocular way to describe it is ‘Slurp, Stir and Serve’…
Figure 1 is awfully familiar to anyone with exposure to traditional ‘Computing 101’ – computers take input, process it, and create output. At its simplest level so does Middleware.

But let’s quickly get more concrete. Figure 2 is our ‘problem scenario’ from part 1 – using a Collections Management System (CollMS) and its data to feed directly to your web users.

Figure 2

Next, Figure 3 puts Middleware in the picture. Immediately the opportunity exists to change what you present to your web audience – because you’re ‘driving’ your web presence from a ‘different system and data-set’ – more formally you have de-coupled your web functionality from your Collections Management System (CollMS). Most importantly your Middleware will (be chosen to and) allow you to design for your web users (and services) rather than be constrained by the functionality of your CollMS.

Figure 3

Figure 3

Now I’ve lulled you in a false sense of simplicity,  let me expand…

Figure 4

Figure 4

In Figure 4  we see a little more detail of how the Middleware part of this looks.

At a conceptual level it’s worth noting that the Middleware ‘box’ was itself described as an input-process-output ‘box’ at its highest level. And inside the Middleware box, to accomplish that, I’ve shown that we’ll need at least two more input-process-output ‘chains’ to achieve our purpose.

This kind of  ‘model’ is valuable in its simplicity – it shows the potential benefit of breaking everything down to a input-process-output ‘tasks’. And, wherever you see a ‘process’ box you can be pretty sure it has its own input-process-output ‘tasks’ inside it. So as the infamous saying goes, in our ‘model’, it really is just ‘turtles all the way down’

So far, so obvious…

More important is that this approach (Figure 4) has some appealing charateristics from a functional and developmental point of view:

  • it’s technology agnostic. It is not reliant on the system (in our case, CollMS) it’s ‘slurping from’. It’s possible to use a different piece of technology for each of the components (datastore, each of the processes) – this has the potential for you to choose ‘best of breed’ technology for each component. Or, more pragmatically, to choose technology your organisation has skills in – i.e. for the ‘Microsoft shop’ they can use .NET stuff, for University environments like ours we can leverage our skills in open source/standard technologies like PHP, XSLT, JSON etc.
  • it’s modular. Modular is good – it allows us to break problems into contained packets which humans can deal with.  Through modularisation the development of such a system can be broken into simpler, smaller, problems – or ‘black boxes’. Modular should also aid sustainability – replacing one piece in a modular system won’t break the rest – if designed properly.
  •  it’s loosely coupled. What’s good about loose coupling is exactly that it’s not like its opposite – a monolithic system. Our Figure 1 shows a simplified monolithic system, where if the CollMS ‘goes down’ everything is down. Conversely in the loosely coupled example, Figure 3, our web users won’t even notice when the CollMS is down because they are being ‘served’ by the Middleware. Loose coupling is most important as a requirement for modularisation – together they enable the ‘black box’ development approach.
  • it can be distributed. Modularisation and loose coupling means that different components of the system can ‘live’ on different machines, even in different localities if desired. In the technical world this characteristic provides us an easier path to deal with issues such as continuity, recoverability & scalability.

A couple of notes before I finish this weeks instalment.

Presentation. I have completely ignored, for simplicity, that generally there is a whole separate layer, or module, between the Middleware and the web user called the presentation layer. It’s crucial, you should be aware it exists, but it would have messed up my simple pictures..

Integration. Another crucial characteristic of Middleware which I’ve chosen to not detail this week.  But it’s not a great stretch to see that if you can ‘slurp’ from one data source, you can do it from many. This is a key in our “Open Book” project – to show how, and document issues, in bringing together (integrating) multiple data sources.

One final point to ponder – when you take the concepts and characteristics outlined here, multiply them many fold, you have a simple conceptual picture of what the web, and in particular the web of data, looks like. A loosely coupled, distributed system, of modules, which are all able to ‘slurp, stir and serve’. You can plug these modules together,  integrate different data sets, create a new modules… you can create new modules which just serve a processing purpose and let others use them… and so on and so on…

In part 3 we’ll look what ‘Open Book’ will ‘build’ as we move ahead in constructing The Fitzwilliam Museum’s ‘explore service(s)’…

P.S. When I decided I wanted to illustrate this blog, my heart sank – I have never really ‘got on’ with the likes of Visio and MS Office Draw… anyway I found a freeware drawing package, yEd, that is great. and made ‘knocking out’ the figures for this post pretty straight forward.

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One response to “It’s Obvious #2

  1. Pingback: Disambiguating metadata « JISC – Open Book Project

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