Tuesday, May 27, 2008
On the concept of Form (3): the Force Field
Warning: :-) this post is going to be somehow conceptual. I'll soon move to some real-world, software-based example, but I really need to introduce some concepts first.
The notion of force field might be unfamiliar to some, so I'll borrow a great example from Alexander himself. Consider your first "requirement" (for a system yet to be built) as a permanent magnet of some size and shape. If you place a flat glass over that magnet, and drop some iron filings on it, the iron will naturally dispose along the magnetic field lines. That gives us an image of [a section of] the force field. Now add another magnet: the shape of the field will change, as the magnets are interacting, thereby shaping a more complex force field.
We can change the [shape of the] field in many ways: moving magnets around, changing their shape, their magnetization, or even adding some shields around magnets.
The great thing about the magnetic field is that we can somehow observe its shape. Indeed, if our goal was to create a form that can be put into effortless contact with the field, we'll just have to replicate the same form that the magnetic field is giving to the iron filings. As Alexander says (NoTSoF, page 21), "once we have a diagram of forces [...] this will in essence also describe the form as a complementary diagram of forces".
In the real world, and even more so in the software world, we are never so lucky: the force field is invisible and tends also to be highly unstable.
Usually, the force field of a software project starts with Requirements. Requirements are often categorized in some way, like "functional" and "nonfunctional", or "user requirements" and "system requirements. However, requirements of any kind are just like magnets: they contribute to shape the overall field.
Requirements are just one kind of force, that is, they are not alone in shaping the field. Many technological choices we make, sometimes very (or too) early, are also shaping the force field.
Consider a simple business application. Once you decide that you'll build a web application, you have added quite a few powerful magnets. If you're familiar with JSP and EJB, you are naturally tempted to choose those technologies early on. That's like adding quite a few powerful magnets again. Or maybe it's like adding a magnetic shield: it really depends on context.
Sometimes, technology makes the field simpler: the right infrastructure should simplify the field, that is, it should act more like a shield than like a magnet. In this sense, infrastructure should be chosen when the dominant forces are known, unlike what happens in many projects, where infrastructure (usually a superstructure in disguise) is chosen too early, thereby making the overall field even more complex.
We also shape the field, so to speak, by choosing what to ignore and what to postpone in any given release. Anything we ignore, like anything we postpone, won't be allowed to shape the field right now.
This is fine, as long as the corresponding magnets will be placed somehow distant from the others (good modularity), possibly with some kind of magnetic shielding in between (stable interfaces). It's also fine if we can ignore it forever. Any attempt to temporarily ignore a strictly interacting force will wreak havoc later on, as our form will no longer match the resulting force field. Refactoring can accommodate minor misfits with the ideal form, but won't help much when the force field changes radically (see also my notes on refactoring here).
Here lies one of the architect's fundamental abilities: the intuitive understanding that something can be beneficially postponed, while something else must be dealt with immediately, because its influence on the force field is so strong that doing otherwise will shift us toward the wrong kind of form.
It is important to understand the role of choice in exploiting instability. Too often, software developers tend to see requirements as "fixed". They don't like to negotiate: it's much easier to fight the compiler than the marketing guys.
A good architect, however, can't miss the opportunity to simplify the field by moving some magnets around. That requires the ability to see the overall picture and the fine details at the same time. Here is Alexander again (page 18): "this ability to deal with several layers of form-context boundaries in concert is an important part of what we often refer to as the designer's sense of organization. The internal coherence of an ensemble depends on a whole net of such adaptations".
That ain't an easy feat. It requires an understanding of the business, the users, and the technology. And even more important, it requires a willingness to act on that knowledge. The power of choice extends to the infrastructure: sometimes, by willingly postponing a technological choice until the force fields takes shape, we can make a better, more "natural" choice.
This can be hard for some developers: they want certainty, and they want it now. In my experience, that goes in pair with the willingness to adopt a sub-optimal, but repetitive and context free solution for a wide class of problems, instead of adopting several optimal, but reasoned and context-dependent solution for smaller classes of problems.
Unfortunately, choosing the "wrong" technology is very much like choosing the wrong shape or orientation for a building. To quote Alexander once again (page 29): "Instead of orienting the house carefully for sun and wind, the builder conceives its organization without concern for orientation, and light, heat, and ventilation are taken care of by fans, lamps, and other kinds of peripheral devices. Bedrooms are not separated from living rooms in plan, but are placed next to one another and the walls between them stuffed with acoustic insulation".
I think we can easily see a parallel with software here: a misfit technology is chosen early on. As a consequence, you find yourself adding more and more technology (fans, lamps, insulation) to satisfy the end-user needs. "Modern" web applications seem to have taken this path: faced with a difficult field, they're layering one technology on top the other, desperately trying to overcome the problems of the previous layer.
Next time, in no particular order: agility, unstable requirements, early coding, TDD, "seeing" the field, internal and external representations, is UML any useful, order within chaos (dominant forces), constructive force field and systematic techniques, and whatever else will come to my mind :-).
The notion of force field might be unfamiliar to some, so I'll borrow a great example from Alexander himself. Consider your first "requirement" (for a system yet to be built) as a permanent magnet of some size and shape. If you place a flat glass over that magnet, and drop some iron filings on it, the iron will naturally dispose along the magnetic field lines. That gives us an image of [a section of] the force field. Now add another magnet: the shape of the field will change, as the magnets are interacting, thereby shaping a more complex force field.
We can change the [shape of the] field in many ways: moving magnets around, changing their shape, their magnetization, or even adding some shields around magnets.
The great thing about the magnetic field is that we can somehow observe its shape. Indeed, if our goal was to create a form that can be put into effortless contact with the field, we'll just have to replicate the same form that the magnetic field is giving to the iron filings. As Alexander says (NoTSoF, page 21), "once we have a diagram of forces [...] this will in essence also describe the form as a complementary diagram of forces".
In the real world, and even more so in the software world, we are never so lucky: the force field is invisible and tends also to be highly unstable.
Usually, the force field of a software project starts with Requirements. Requirements are often categorized in some way, like "functional" and "nonfunctional", or "user requirements" and "system requirements. However, requirements of any kind are just like magnets: they contribute to shape the overall field.
Requirements are just one kind of force, that is, they are not alone in shaping the field. Many technological choices we make, sometimes very (or too) early, are also shaping the force field.
Consider a simple business application. Once you decide that you'll build a web application, you have added quite a few powerful magnets. If you're familiar with JSP and EJB, you are naturally tempted to choose those technologies early on. That's like adding quite a few powerful magnets again. Or maybe it's like adding a magnetic shield: it really depends on context.
Sometimes, technology makes the field simpler: the right infrastructure should simplify the field, that is, it should act more like a shield than like a magnet. In this sense, infrastructure should be chosen when the dominant forces are known, unlike what happens in many projects, where infrastructure (usually a superstructure in disguise) is chosen too early, thereby making the overall field even more complex.
We also shape the field, so to speak, by choosing what to ignore and what to postpone in any given release. Anything we ignore, like anything we postpone, won't be allowed to shape the field right now.
This is fine, as long as the corresponding magnets will be placed somehow distant from the others (good modularity), possibly with some kind of magnetic shielding in between (stable interfaces). It's also fine if we can ignore it forever. Any attempt to temporarily ignore a strictly interacting force will wreak havoc later on, as our form will no longer match the resulting force field. Refactoring can accommodate minor misfits with the ideal form, but won't help much when the force field changes radically (see also my notes on refactoring here).
Here lies one of the architect's fundamental abilities: the intuitive understanding that something can be beneficially postponed, while something else must be dealt with immediately, because its influence on the force field is so strong that doing otherwise will shift us toward the wrong kind of form.
It is important to understand the role of choice in exploiting instability. Too often, software developers tend to see requirements as "fixed". They don't like to negotiate: it's much easier to fight the compiler than the marketing guys.
A good architect, however, can't miss the opportunity to simplify the field by moving some magnets around. That requires the ability to see the overall picture and the fine details at the same time. Here is Alexander again (page 18): "this ability to deal with several layers of form-context boundaries in concert is an important part of what we often refer to as the designer's sense of organization. The internal coherence of an ensemble depends on a whole net of such adaptations".
That ain't an easy feat. It requires an understanding of the business, the users, and the technology. And even more important, it requires a willingness to act on that knowledge. The power of choice extends to the infrastructure: sometimes, by willingly postponing a technological choice until the force fields takes shape, we can make a better, more "natural" choice.
This can be hard for some developers: they want certainty, and they want it now. In my experience, that goes in pair with the willingness to adopt a sub-optimal, but repetitive and context free solution for a wide class of problems, instead of adopting several optimal, but reasoned and context-dependent solution for smaller classes of problems.
Unfortunately, choosing the "wrong" technology is very much like choosing the wrong shape or orientation for a building. To quote Alexander once again (page 29): "Instead of orienting the house carefully for sun and wind, the builder conceives its organization without concern for orientation, and light, heat, and ventilation are taken care of by fans, lamps, and other kinds of peripheral devices. Bedrooms are not separated from living rooms in plan, but are placed next to one another and the walls between them stuffed with acoustic insulation".
I think we can easily see a parallel with software here: a misfit technology is chosen early on. As a consequence, you find yourself adding more and more technology (fans, lamps, insulation) to satisfy the end-user needs. "Modern" web applications seem to have taken this path: faced with a difficult field, they're layering one technology on top the other, desperately trying to overcome the problems of the previous layer.
Next time, in no particular order: agility, unstable requirements, early coding, TDD, "seeing" the field, internal and external representations, is UML any useful, order within chaos (dominant forces), constructive force field and systematic techniques, and whatever else will come to my mind :-).
Labels: architecture, design, form, requirements
Tuesday, May 13, 2008
Natural language
Some (most :-) of my clients are challenging. Sometimes the challenge comes from the difficult technical problems they face. That's the best kind of challenge.
Sometimes the challenge comes from people: that's the worst kind of challenge, and one that right now is better left alone.
Sometimes the challenge comes from the organization, which means it also comes from people, but with a different twist. Challenges coming from the organization are always tough, but overcoming those challenges can really make a difference.
One of my challenging clients is a rather large company in the financial domain. They are definitely old-school, and although upper management can perfectly see how software is permeating and enabling their business, middle management tend to see software as a liability. In their eternal search for lower costs, they moved most of the development offshore, keeping only an handful of designers and all the analysts in-house. Most often, design is done offshore as well, for lack of available designers on this side of the world.
Analysts have a tough job there. On one side, they have to face the rest of the company, which is not software-friendly. On the other side, they have to communicate clear requirements to the offshore team, especially to the designers, who tend to be very technology-oriented.
To make things more complicated, the analysts often find themselves working on unfamiliar sub-domains, with precise regulations but also with large gray areas that must be somehow understood and communicated.
Icing on the cake: some of those financial instruments do not even exist in the local culture of the offshore team, making communication as difficult as ever.
Given this overall picture, I've often recommended analysts to spend some time creating a good domain model (usually, a UML class diagram, occasionally complemented by some activity diagrams).
The model, with unambiguous associations, dependencies, multiplicities, and so on, will force them to ask the right questions, and will make it easier for the offshore designer to acquaint himself with the problem. Over time, this suggestion has been quite helpful.
However, as I said, the organization is challenging. Some of the analysts complained that their boss is not satisfied by a few diagrams. He wants a lengthy, wordy explanation, so he can read it over and see if they got it right (well, that's his theory anyway). The poor analyst can't possibly do everything in the allotted time.
Now, I always keep an eye on software engineering research. I've seen countless attempts to create UML diagrams from natural language specifications. The results are usually unimpressive.
In this case, however, I would need exactly the opposite: a tool to generate a precise, yet verbose domain description out of a formal domain model. The problem is much easier to solve, especially because analysts can help the tool, by using the appropriate wording.
Guess what, the problem must be considered unworthy, because there is a dearth of works in that area. In practice, the only relevant paper I've been able to find is Generating Natural Language specifications from UML class diagrams by Farid Meziane, Nikos Athanasakis and Sophia Ananiadou. There is also Nikos' thesis online, with a few more details.
The downside is that (as usual) the tool they describe does not seem to be generally available. I've yet to contact the authors: I just hope it doesn't turn out to be one of those Re$earch Tool$ that never get to be used.
From the paper above, I've also learnt about ModelExplainer , a similar tool from a commercial company. Again, the tool doesn't seem to be generally available, but I'll get in touch with people there and see.
Overall, the problem doesn't seem so hard, especially if we accept the idea that the analyst will help the tool, choosing appropriate wording. An XMI-to-NL (Natural Language) would make for a perfect open source project. Any takers? :-)
Sometimes the challenge comes from people: that's the worst kind of challenge, and one that right now is better left alone.
Sometimes the challenge comes from the organization, which means it also comes from people, but with a different twist. Challenges coming from the organization are always tough, but overcoming those challenges can really make a difference.
One of my challenging clients is a rather large company in the financial domain. They are definitely old-school, and although upper management can perfectly see how software is permeating and enabling their business, middle management tend to see software as a liability. In their eternal search for lower costs, they moved most of the development offshore, keeping only an handful of designers and all the analysts in-house. Most often, design is done offshore as well, for lack of available designers on this side of the world.
Analysts have a tough job there. On one side, they have to face the rest of the company, which is not software-friendly. On the other side, they have to communicate clear requirements to the offshore team, especially to the designers, who tend to be very technology-oriented.
To make things more complicated, the analysts often find themselves working on unfamiliar sub-domains, with precise regulations but also with large gray areas that must be somehow understood and communicated.
Icing on the cake: some of those financial instruments do not even exist in the local culture of the offshore team, making communication as difficult as ever.
Given this overall picture, I've often recommended analysts to spend some time creating a good domain model (usually, a UML class diagram, occasionally complemented by some activity diagrams).
The model, with unambiguous associations, dependencies, multiplicities, and so on, will force them to ask the right questions, and will make it easier for the offshore designer to acquaint himself with the problem. Over time, this suggestion has been quite helpful.
However, as I said, the organization is challenging. Some of the analysts complained that their boss is not satisfied by a few diagrams. He wants a lengthy, wordy explanation, so he can read it over and see if they got it right (well, that's his theory anyway). The poor analyst can't possibly do everything in the allotted time.
Now, I always keep an eye on software engineering research. I've seen countless attempts to create UML diagrams from natural language specifications. The results are usually unimpressive.
In this case, however, I would need exactly the opposite: a tool to generate a precise, yet verbose domain description out of a formal domain model. The problem is much easier to solve, especially because analysts can help the tool, by using the appropriate wording.
Guess what, the problem must be considered unworthy, because there is a dearth of works in that area. In practice, the only relevant paper I've been able to find is Generating Natural Language specifications from UML class diagrams by Farid Meziane, Nikos Athanasakis and Sophia Ananiadou. There is also Nikos' thesis online, with a few more details.
The downside is that (as usual) the tool they describe does not seem to be generally available. I've yet to contact the authors: I just hope it doesn't turn out to be one of those Re$earch Tool$ that never get to be used.
From the paper above, I've also learnt about ModelExplainer , a similar tool from a commercial company. Again, the tool doesn't seem to be generally available, but I'll get in touch with people there and see.
Overall, the problem doesn't seem so hard, especially if we accept the idea that the analyst will help the tool, choosing appropriate wording. An XMI-to-NL (Natural Language) would make for a perfect open source project. Any takers? :-)
Labels: analysis, article reference, profession, requirements, tools
