No, your example would mean that it’s an schema:Article and a pto:Dog_breed.

To state what the schema:Article is about, you could use its about property.

The elaborate version would be:

<article itemscope itemtype="http://schema.org/Article">

  <div itemprop="about" itemscope itemtype="http://schema.org/Intangible">
    <link itemprop="additionalType" href="http://www.productontology.org/id/dog_breed" />
    <!-- properties about dog breed(s) -->
  </div>

  <!-- properties about the article -->

</article>

Notes:

• Schema.org has no class for dog breeds, so you’d have to choose the closest broader class. I think it would be schema:Intangible; otherwise the top class schema:Thing.

• Using pto:Dog_breed means that the article is about the concept of dog breeds, or dog breeds in general, but not about a specific dog breed.

No, your example would mean that it’s an schema:Article and a pto:Dog_breed.

To state what the schema:Article is about, you could use its about property.

The elaborate version would be:

<article itemscope itemtype="http://schema.org/Article">

  <div itemprop="about" itemscope itemtype="http://schema.org/Intangible">
    <link itemprop="additionalType" href="http://www.productontology.org/id/Dog_breed" />
    <!-- properties about dog breed(s) -->
  </div>

  <!-- properties about the article -->

</article>

Notes:

• Schema.org has no class for dog breeds, so you’d have to choose the closest broader class. I think it would be schema:Intangible; otherwise the top class schema:Thing.

• Using pto:Dog_breed means that the article is about the concept of dog breeds, or dog breeds in general, but not about a specific dog breed.

• It should be …/id/Dog_breed, not …/id/dog_breed (URIs are case-sensitive).