In this section we're going to continue our discussion about hierarchy and composition within the interface. And we're going to look at some ideas concerning conventions and expectations for both the web and apps. Our screens are often divided up in very conventional ways and as user interface designers we have to figure out how to use these conventions. But also create some kind of variables within them. In terms of scale and visual attention, our content area is normally the most important. Followed by branding and a couple of levels of navigation or functionality. Before we figure out any details of the design we have to figure out the relationship between these four different areas. And each of these areas is somewhat self contained. So we could spend a great deal of time working on the elements and components of each of these individual areas. The simplest structural division that we can make is between the content that might change frequently and the elements that might remain stable. Such as the branding and navigation, which gives us a familiar and standard relationship between the header and the body of our website. And once we've isolated these larger areas or divisions we can start to think about how they might be structured in more detail. If we look at the body of this simple website, for instance, we could have a number of different things going on in that one area. It doesn't have to be a single image or a single activity, there could be multiple things happening at the same time. And as soon as we have multiple things happening our job as an interface designer becomes more complicated. We have to start to think about spacing and structure, organization, and hierarchy. Conventions and familiar structures can help us deal with these things quite quickly and easily. The web is often more concerned with the content that's in the structure than the structure itself. That structure quite often has to be functional and fairly invisible. So it's okay if it's familiar to some extent. Our expectation of the website is that there are multiple things happening on one screen. We have a larger surface area so it makes sense that there's more going on. But when we start to look at a phone and look at apps on our phone, it's not quite the same. Instead of four things happening on one screen, it's often one thing happening on four screens. And those screens work together to form a sequence of events. So our branding might be on a totally separate screen before we get to our content. And even if we wanted to reiterate our branding it would have to be done at a smaller scale. Because we have very little real estate on the screen of the phone. So where everything is laid out in front of us on a web page, for instance, on an app everything is hidden, or condensed, or sequential. So quite often our navigation is invisible until we need it. And any interaction will normally eclipse the previous screen. So the components that make up a web experience in a single page might have to be spread across multiple screens for an app on the phone. Which intrinsically means we're traveling from screen to screen on the phone, which is a little more of a fluid experience. Which explains why even though a website and an app are both screen based experiences, they actually feel very different. Even if they have the same content the app feels much more fluid. So while our content here is divided across a number of different pages. There's definitely going to be some pages where more of the elements are going to need to exist at the same time. And, again, there are formal conventions built around functionality that we adhere to. And that could be where our branding appears, how our navigation works with a swipe, or even where our menu bar is, or what's in that menu bar. And these conventions are constantly changing. We're moving towards that more fluid immersive experience we talked about so we want all of our navigation and other elements to be hidden. And if we're going to travel to other screens we want to do that in a fluid way, not by clicking, but by swiping and scrolling. Our phones act as windows, we can only see a small amount of content on them. But we know there's a much bigger world out there that we can move around in. So while we might only get one piece of information or experience at a time, we know there are thousands more outside the visible realm of our window. And that poetic explanation has some practical implications. We don't want anything to get in the way of our window, to get in the way of our small amount of content we're looking at, our experience. So our menus become hidden or as invisible as possible. On our website our five primary options might be laid out on display, but on an app they're condensed and hidden. They live in a menu that we don't see until we want to. And that menu itself is evolving, again, to be more fluid. So instead of just being a drop down menu, which feels like a web convention, we're now much more used to having menus come in from the side with a swipe. And be much more smooth and fluid. The user interface for our apps our like Swiss Army knives, they have multiple functionality. But everything is packed away until you need that specific tool and when you need a tool there's many different things to choose from. And they, generally, are really good at doing just one thing. But until you need them they remain packed away, they remain invisible. If the website let's it all hang out on display, the app is much more based on a philosophy of being hidden until needed. Our menus and navigation shouldn't get in the way of the small visual field that is our only place to show content. Even if we wanted to unpack our options there'd be no room for us to lay them all out on the screen. If we have more than a couple of options we're going to have to compact them down and create an interface element that can hide them. We want to make sure that our user is focussing on the content on our small screen. And because we have little real estate it means that we have to feed them tasks one at a time. And because of this our apps tend to be more focused on being very successful at a very localized and specific task. When we need more real estate for complex tasks we tend to switch to the computer screen. And this fundamentally affects what kind of content or activity works well on what kind of screen. For the UI designer it also shapes and structures what we do. There are set conventions related to what works best on these screens that we just can't escape. We have to figure out how to get the most out of those conventions.