Basics of edge-side composition
Edge-side composition may be the oldest pattern besides the web approach – if we reduce the web approach to purely taking links, that is. As you already know, techniques such as SSI and, later, ESI were only invented to place fragments of HTML on an HTML page. This was a simple yet flexible way to create reusable layouts.
Of course, when SSI was introduced, content delivery networks (CDNs) and distributed development weren't around. However, as we saw in the previous chapter, the use of SSI or its successor, ESI, may be a great choice when you're looking for a good way of denoting UI insertion points. The best argument in favor of using SSI or ESI is its widespread adoption and the clear rules governed by a specification.
As in the previous chapters, first, we will go over the architecture before doing a sample implementation. Finally, we will touch on some potential enhancements for our sample implementation.
