3. "Accession" vs. "Other Goods." This section distinguishes among the "accession," the "other goods," and the "whole." The last term refers to the combination of the "accession" and the "other goods." If one person's collateral becomes physically united with another person's collateral, each is an "accession."

Example 1: SP-1 holds a security interest in the debtor's tractors (which are not subject to a certificate-of-title statute), and SP-2 holds a security interest in a particular tractor engine. The engine is installed in a tractor. From the perspective of SP-1, the tractor becomes an "accession" and the engine is the "other goods." From the perspective of SP-2, the engine is the "accession" and the tractor is the "other goods." The completed tractor-tractor cum engine-constitutes the "whole."

4. Scope. This section governs only a few issues concerning accessions. Subsection (a) [Maine cite subsection (1)] contains rules governing continuation of a security interest in an accession. Subsection (b) [Maine cite subsection (2)] contains a rule governing continued perfection of a security interest in goods that become an accession. Subsection (d) [Maine cite subsection (4)] contains a special priority rule governing accessions that become part of a whole covered by a certificate of title. Subsections (e) and (f) [Maine cite subsections (5) and (6)] govern enforcement of a security interest in an accession.

5. Matters Left to Other Provisions of This Article: Attachment and Perfection. Other provisions of this Article often govern accession-related issues. For example, this section does not address whether a secured party acquires a security interest in the whole if its collateral becomes an accession. Normally this will turn on the description of the collateral in the security agreement.

Example 2: Debtor owns a computer subject to a perfected security interest in favor of SP-1. Debtor acquires memory and installs it in the computer. Whether SP-1's security interest attaches to the memory depends on whether the security agreement covers it.

Similarly, this section does not determine whether perfection against collateral that becomes an accession is effective to perfect a security interest in the whole. Other provisions of this Article, including the requirements for