Monday, April 17 2006
Work on my web calendar project has taken a strongly theoretical turn, with me trying to think how I can represent generic data relationships in which the fields of one table could be the primary keys of another, but which table they were primary keys of would vary depending on the contents of a field in a third table. This might sound like an unusual situation in the world of data relationships, but it's actually rather common. I've been thinking how to handle such relationships in my generic MySQL web frontend but as of yet the issue has caused me to do a lot of blank staring out over the railing of my laboratory deck. Being an unusually dry April, the weather has been perfect for such contemplation.
When I wanted real distraction from such mentally-intensive matters, today I went on a crack patrol. This involved surveying all the various masonry projects I've completed over the past few years looking for cracks that have subsequently formed. The other day I noticed an eighth-inch-wide vertical crack in the concrete block retaining wall just uphill from the southwest corner of the house, a wall I disassembled and then rebuilt in September of 2004. The crack coincided with a place in the wall where I'd been forced to stack blocks directly on top of each other without overlap. Today I repaired that crack with a reinforced masonry stucco technique I'd developed months after that retaining wall project. It's the method I'd used to finish the surfaces of the basement walls I'd repaired last summer. It involved embedding lots of overlapping pieces of fiberglass drywall mesh into pure Portland cement, which I obsessively spray with water until it sets to a flinty hardness. That technique seems to have worked miracles in the basement guest room closet, where a careful inspection revealed absolutely no cracks, not even of the tiniest size. But an inspection of the basement linen closet (completed more recently) revealed three or four barely-visible hairline cracks running up the wall from floor to ceiling. I'd used many layers of Portland cement and mesh tape on that wall, augmented with iron wires. But I'd oriented the iron reinforcment vertically, aimed at preventing horizontal cracks (which had been the main problem in that wall).
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