Language for Specifing Data Streams

The ACSetSpec DSL is basically ready to be the stream language. You just need to add fields for valence (add/delete/merge) and timestamps.

https://github.com/AlgebraicJulia/ACSets.jl/blob/0c5b06649ea6678d2f5668559d8c933f971b62b6/src/ADTs.jl#L22

Instead of:

```julia
@as_record struct Statement <: AbstractACSetSpec
table::Symbol
element::Vector{Args}
end

@as_record struct ACSetSpec <: AbstractACSetSpec
acstype::Union{Symbol,Expr}
body::Vector{Statement}
end
```

You could use:

```julia
@data TimedStatement <: AbstractACSetSpec
Add(s::Statement, t::Time)
Delete(s::Statement, t::Time)
Merge(table::Symbol, part1::Int, part2::Int, t::Time)
end

@as_record struct ACSetSpecSteam <: AbstractACSetSpec
acstype::Union{Symbol,Expr}
body::Vector{TimedStatement}
end
```

And then write an interpreter that takes an ADT in that DSL and gives you a temporal sheaf