Draft: Key expressions, first blog #29
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p-avital
changed the title
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| # The KE Tree: a Zenoh flavoured data structure. | ||
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| One thing you might have noticed is that with all these slashes, KEs definitely take after paths. One other aspect they take from paths is their intrisic hierarchical nature: like most good address spaces, KEs are hierarchical. |
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I had to think twice to understand the phrase "KEs definitely take after paths"
| 1. If the KEs define disjoint sets (where there doesn't exist a key that belongs to both), they just don't interract. | ||
| 2. If the operation KE and the existing data's KE define sets that have keys in common, like `a/*` and `*/b` both contain the `a/b` key, they are said to _intersect_. That means the operation will affect at least a subset of the existing data. Intersection is always symmetric: A intersects with B implies that B intersects with A. | ||
| 3. If the operation KE's set contains all keys defined by the existing data's KE, the operation KE is said to _include_ the existing data KE. This means that the operation will affect _all_ of the existing data. Note that inclusion is generally asymmetric, but that "A includes B" or "B includes A" implies that "A and B intersect". | ||
| 4. If the operation KE and data KE define the same set, they are equal. This is the only situation where inclusion is symmetrical, and thanks to our previously discussed [3 steps program](#specifying-the-kel), this is equivalent to string equality. |
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to our previously discussed 3 steps program -> can you now tell the truth that it was 4 steps ? :)
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Edit-misread.
It's still called a "3 steps program" , that's just its name :p
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| Inclusion is a bit more "optimizy": if some writes to A that includes B and C, the records for B and C may be erased, since A has now taken over both of their regions on interest. | ||
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| Equality and disjunction are generally not very useful: equality because inclusion is generally sufficient for most optimizations, and disjunction because it usually just means that two things do not care about each other, which we in turn don't care about. |
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I think this sentence would be better as a footnote
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I don't really disagree, considering it's not key information; it just feels more natural to me to include all 4 relations in the same flow rather than interrupting it with an indirection. Plus, I wouldn't really know where to put the footnote marker x)
| One of the major changes introduced by Zenoh 0.6 Bahamut was a new definition of the [Key Expression Language](https://github.com/eclipse-zenoh/roadmap/blob/main/rfcs/ALL/Key%20Expressions.md). | ||
| With Zenoh 0.7.1, we introduce new data structures that let you interact with this language more easily than ever before. | ||
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| Come with me on a journey into Zenoh's vision of a Named Data Address Space: Key Expressions (KE). The major parts of this post are all rather independent, so feel free to skip past one if it's not to your taste. |
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skip past one?
"if it's not your taste" looks better to me.
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Was hard to read, but interesting. Proposals available here (comments where not really usable :) ) : #31 |
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