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ISO Geometry factory not available

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Joined: 1 year ago
Posts: 72614
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I'm using Geotools 30-SNAPSHOT and i would like to use ISO Geometry (from opengis package).

I'm using the following code to get ISO geometry related factories:

import org.geotools.geometry.GeometryFactoryFinder;
import org.geotools.referencing.crs.DefaultGeographicCRS;
import org.geotools.util.factory.Hints;
import org.opengis.geometry.PositionFactory;
import org.opengis.geometry.coordinate.GeometryFactory;
import org.opengis.geometry.primitive.PrimitiveFactory;

public class FactoriesSample {

    
    public static void main(String[] args) {
        PositionFactory positionFactory ;
        PrimitiveFactory primitiveFactory;
        GeometryFactory gf;

        Hints hints = new Hints( Hints.CRS, DefaultGeographicCRS.WGS84 );
                
        try {
          positionFactory = GeometryFactoryFinder.getPositionFactory(hints);
        } catch (Exception e) {
          System.out.println("Cannot determine geometry factory: "+e.getMessage());
        }

        try {
          primitiveFactory  = GeometryFactoryFinder.getPrimitiveFactory(hints);
        } catch (Exception e) {
          System.out.println("Cannot determine primitive factory: "+e.getMessage());
        }

        try {
          gf     = GeometryFactoryFinder.getGeometryFactory(hints);
        } catch (Exception e) {
          System.out.println("Cannot determine geometry factory: "+e.getMessage());
        }
    }   
}

My concern is that the execution of the previous code gives:

Cannot determine geometry factory: No factory of type "PositionFactory" has been found.
Cannot determine primitive factory: No factory of type "PrimitiveFactory" has been found.
Cannot determine geometry factory: No factory of type "GeometryFactory" has been found.

It seems that my project has no attached JAR that contains the factories. My maven dependencies are:

<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-epsg-extension</artifactId>
    <version>${geotools.version}</version>
</dependency>

<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-epsg-hsql</artifactId>
    <version>${geotools.version}</version>
</dependency>
            
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-geotiff</artifactId>
    <version>${geotools.version}</version>
</dependency>
            
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-image</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-main</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-metadata</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-opengis</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-referencing</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-shapefile</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-swing</artifactId>
    <version>${geotools.version}</version>
</dependency>  
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-transform</artifactId>
    <version>${geotools.version}</version>
</dependency>  
        
<dependency>
    <groupId>org.geotools</groupId>
    <artifactId>gt-xml</artifactId>
    <version>${geotools.version}</version>
</dependency> 
        
<dependency>
    <groupId>org.geotools.xsd</groupId>
    <artifactId>gt-xsd-core</artifactId>
    <version>${geotools.version}</version>
</dependency>  
        
<dependency>
    <groupId>org.geotools.xsd</groupId>
    <artifactId>gt-xsd-gml2</artifactId>
    <version>${geotools.version}</version>
</dependency>
        
<dependency>
    <groupId>org.geotools.xsd</groupId>
    <artifactId>gt-xsd-gml3</artifactId>
    <version>${geotools.version}</version>
</dependency>   

Can you please indicate me which dependencies are missing in order to get the factories or is there is an error within my code ?

Thanks a lot.


   
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$begingroup$

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$begingroup$

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Theorem 5.1: Let $Asubsetmathbb{R}^n$ be a Borel set with $text{dim}A=sleq1$. Then for all $tin[0,s]$
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begin{align*}
I_sigma(mu_e) = int_{-infty}^inftyint_{-infty}^infty |x-y|^{-sigma},dmu_ex,dmu_ey &= int_{mathbb{R}^n}int_{mathbb{R}^n} |ecdotxi – ecdotzeta|^{-sigma},dmu xi,dmuzeta \
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&= int_{mathbb{R}^n}int_{mathbb{R}^n} |xi – zeta|^{sigma},dmuxi,dmuzeta\
&= I_sigma(mu),
end{align*}

where I’m using that because $ein S^{n-1}$ then $|e| =1$. But then I get stuck and I do not know how to continue with the calculations, because the set
$${ ein S^{n-1} : I_sigma(mu)=infty }$$
doesn’t make sense to me, maybe my previous calculation is wrong.

$endgroup$

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$begingroup$

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Hi! I am reading Cox’s “Primes of the Form $x^2 + ny^2$“, and am on Chapter 5 (it’s a speedrun from number fields to Hilbert’s class field). I am attempting exercise 5.1, and I have done some parts, so I am both asking for verification for my solution as well as hints for the rest.

Things we have stated:

Proposition 5.3. For a number field $K$

(i) $mathcal{O}_K$ is a subring of $mathbb{C}$ whose field of fractions is $K$.

(ii) $mathcal{O}_K$ is a free $mathbb{Z}$-module of rank $[K : mathbb{Q}]$.


(a) Show that a nonzero ideal $mathfrak{a}$ of $mathcal{O}_K$ contains a nonzero integer $m$. (Hint: …)

My solution: Let $alpha neq 0$ be in $mathfrak{a}$. Of course it is algebraic, so let the monic integer polynomial $f(x) = a_0 + a_1x + cdots + a_{n – 1}x^{n – 1} + x^n$ be its minimal polynomial. Now, $langle alpha rangle subset mathfrak{a}$. In particular, for all integers $i geq 1$, the elements $alpha^i$ are in $mathfrak{a}$. This then means $sum_{i geq 1} a_i alpha^i in mathfrak{a}$, and since $f(alpha) = 0 in mathfrak{a}$, we have $m = a_0 in mathfrak{a}$.


(b) Show that $mathcal{O}_K / mathfrak{a}$ is finite whenever $mathfrak{a}$ is a nonzero ideal of $mathcal{O}_K$. Hint: if $m$ is the integer from (a), consider the surjection $mathcal{O}_K / mmathcal{O}_K to mathcal{O}_K / mathfrak{a}$. Use part (ii) of Proposition 5.3 to compute the order of $mathcal{O}_K / mmathcal{O}_K$.

My Ideas: From above, we know that $langle m rangle subset langle alpha rangle subset mathfrak{a}$, so my intuition tells me that this surjection definitely exists. (In my intuition, everything’s a module / vector space, so this surjection is just a projection map?) However, I don’t know how to explicitly describe it.

To compute $left|mathcal{O}_K / mmathcal{O}_Kright|$, from the proposition above we know that $mathcal{O}_K cong mathbb{Z}^{[K : mathbb{Q}]}$, so $mathcal{O}_K / mmathcal{O}_K$ is just $left(mathbb{Z} / mmathbb{Z}right)^{[K : mathbb{Q}]}$ and the order is $m^{[K : mathbb{Q}]}$. This part makes sense but feels a little hand wavy? Or is it justified as is?


(c) Use (b) to show that every nonzero ideal of $mathcal{O}_K$ is a free $mathbb{Z}$-module of rank $[K : mathbb{Q}]$.

My solution: Fix a nonzero ideal $mathfrak{a} subset mathcal{O}_K$. We know that $mathcal{O}_K / mathfrak{a}$ is finite and $mathcal{O}_K cong mathbb{Z}^{[K : mathbb{Q}]}$, so $mathfrak{a}$ has to be a product of $[K : mathbb{Q}]$ infinite subgroups of $mathbb{Q}$, i.e. $mathfrak{a} cong prod_{i = 1}^{[K : mathbb{Q}]} m_imathbb{Z}$. This is easy to prove by a simple proof by contradiction.


(d) If we have ideals $mathfrak{a}_1 subset mathfrak{a}_2 subset cdots$, show that there is an integer $n$ such that $mathfrak{a}_n = mathfrak{a}_{n + 1} = cdots$. Hint: consider the surjections $mathcal{O}_K / mathfrak{a}_1 to mathcal{O}_K / mathfrak{a}_2 to cdots$, and use (b).

My solution: Again, my intuition tells me the surjections $mathcal{O}_K / mathfrak{a}_i to mathcal{O}_K / mathfrak{a}_{i + 1}$ exists, but I don’t know how to construct them. Anyways, I claim that if $mathfrak{a}_i neq mathfrak{a}_{i + 1}$, then $left|mathcal{O}_K / mathfrak{a}_{i + 1}right| < left|mathcal{O}_K / mathfrak{a}_iright|$. This holds because for $alpha in mathfrak{a}_{i + 1} setminus mathfrak{a}_i$ is a nonzero element in the kernel of the surjection. Since the quotients are finite, it must eventually stop and hence there are no infinite ascending chains.


(e) Use (b) to show that a nonzero prime ideal of $mathcal{O}_K$ is maximal.

My ideas: Let $mathfrak{a}$ be a prime ideal of $mathcal{O}_K$, and suppose that $mathfrak{a} supset mathfrak{b}$ (i.e. $mathfrak{a}$ is not maximal), which gives $mathcal{O}_K / mathfrak{b} subset mathcal{O}_K / mathfrak{a}$. Thinking about everything as $mathbb{Z}$-modules, we can write $mathcal{O}_K cong prod_{i = 1}^{[K : mathbb{Q}]} mathbb{Z}$ as ordered coordinates, and similar that $mathcal{O}_K / mathfrak{b} cong prod_{i = 1}^{[K : mathbb{Q}]} mathbb{Z} / m_i mathbb{Z}$ and $mathcal{O}_K / mathfrak{a} cong prod_{i = 1}^{[K : mathbb{Q}]} mathbb{Z} / n_i mathbb{Z}$. By the inclusion, we know that $m_i mid n_i$, and for at least one $j$, $m_j neq n_j$. However, for such $j$ we have that $n_j = m_j cdot left(frac{n_j}{m_j}right)$ i.e. $mathbb{Z} / n_j mathbb{Z}$ is not an integral domain, and hence the product ring is not an integral domain, which means $mathfrak{a}$ is not prime.


For you for your help in advance!

enter image description here

$endgroup$

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