Add vcf-rdfizer-policy: ODRL policy attachment with declared selectors and partitions

conda-recipe/meta.yaml

@@ -17,6 +17,7 @@ build:
     - vcf-rdfizer=vcf_rdfizer:main
     - vcf-rdfizer-rules=vcf_rdfizer_rules:main
     - vcf-rdfizer-link=vcf_rdfizer_link:main
+    - vcf-rdfizer-policy=vcf_rdfizer_policy:main
 
 requirements:
   host:
@@ -36,16 +37,20 @@ test:
     - vcf-rdfizer --help
     - vcf-rdfizer-rules --help
     - vcf-rdfizer-link list
+    - vcf-rdfizer-policy --version
     # The vendored vocabulary is package data, not code, so no import touches
     # it: a dropped package-data glob would pass every check above and only
     # surface when SHACL validation runs. One file per glob in pyproject.toml.
     - python -c "import importlib.resources as r; d = r.files('vcf_rdfizer_data'); assert d.joinpath('VOCABULARY_PROVENANCE.json').is_file() and d.joinpath('shacl').joinpath('vcf-4.5.shacl.ttl').is_file() and d.joinpath('ontology').joinpath('vcf-core-vocabulary.bundle.ttl').is_file()"
+    # The policy plug-in's profile and default purpose vocabulary are package data too.
+    - python -c "import importlib.resources as r; d = r.files('vcf_rdfizer_data.policy'); assert d.joinpath('vcf-core-profile.ttl').is_file() and d.joinpath('duo-subset.ttl').is_file()"
   imports:
     - vcf_rdfizer
     # The vocabulary terms, VCF-version model and lexical parsers. Importing it
     # here catches a packaging miss that would otherwise only surface at
     # conversion time, since vcf_rdfizer imports it at module load.
     - vcf_rdfizer_vocab
+    - vcf_rdfizer_policies
 
 about:
   home: https://github.com/ecrum19/VCF-RDFizer

docs/README.md

@@ -54,6 +54,12 @@ deciding whether the tool fits your problem, read
   graph: an ODRL profile with graph selectors, three enforcement tiers, and
   verification — plus a candid account of why access control is not
   anonymization when the genotypes are themselves identifiers.
+- **[Policy attachment v0.1.0](policy-demonstrator.md)** — *implemented;
+  walkthrough in `examples/policy/`.* The first slice of the privacy design:
+  ODRL policies attached to any resource or declared graph selection, a
+  partition rule that says what a withheld resource takes with it, per-request
+  release views, and checks — including a VCF-text oracle — that each view
+  withholds exactly what it should. Selectors and partitions are Turtle, not code.
 
 ### What the graph looks like
 

docs/limitations.md

@@ -267,7 +267,12 @@ record what an artifact was permitted to contain. Three consequences today:
   amount of label removal makes a released genotype graph non-identifying.
 
 The plan is [`privacy-policy-design.md`](privacy-policy-design.md), which is
-explicit that what it offers is *governed release*, not anonymization.
+explicit that what it offers is *governed release*, not anonymization. Its first
+slice exists as a demonstrator, [`vcf-rdfizer-policy`](policy-demonstrator.md)
+v0.1.0: ODRL policies on files and on declared graph selections (region and
+variant ship; others are Turtle declarations), verified release views, in
+memory and after conversion. It changes none of the points above for a
+graph produced by a normal conversion.
 
 **No clinical claims.** The tool transcribes a VCF. It does not interpret,
 annotate, prioritize, or assess pathogenicity, and its output should not be

docs/privacy-policy-design.md

@@ -6,6 +6,12 @@ contract before code depends on it — and, in this case, to be explicit about
 what a policy layer can and cannot achieve, because the failure mode of a
 privacy feature is a false sense of safety.*
 
+*The first slice is implemented and specified separately:
+[`policy-demonstrator.md`](policy-demonstrator.md), v0.1.0 — ODRL attached to
+files, regions and variants over single-sample fixtures, with per-request views
+verified against an oracle. It implements a subset of this document and cites
+the sections it defers.*
+
 VCF-RDFizer currently makes one decision about disclosure: it converts
 everything. Every sample, every genotype, every header line, every free-text
 `Description` goes into the graph, and every artifact is all-or-nothing. The

docs/roadmap.md

@@ -141,7 +141,10 @@ The proposal is an ODRL profile whose assets are **graph selectors** (by class,
 predicate, sample, genomic region, declared field or pattern), compiled to a
 release plan and enforced at the cheapest available point in the existing
 pipeline — TSV pre-filtering, emitter-time filtering, or a post-hoc pass.
-Full design in [`privacy-policy-design.md`](privacy-policy-design.md).
+Full design in [`privacy-policy-design.md`](privacy-policy-design.md). The first
+slice, a v0.1.0 demonstrator over single-sample fixtures, is specified in
+[`policy-demonstrator.md`](policy-demonstrator.md); its §10 maps later versions
+onto the full design's build order.
 
 Two findings from that design are worth surfacing here because they affect work
 outside it:

examples/policy/P001.vcf

@@ -0,0 +1,46 @@
+##fileformat=VCFv4.3
+##fileDate=20260925
+##source=vcf-rdfizer-policy-demonstrator-fixture
+##reference=GRCh38
+##contig=<ID=chr1,length=248956422,assembly=GRCh38>
+##contig=<ID=chr17,length=83257441,assembly=GRCh38>
+##contig=<ID=chr19,length=58617616,assembly=GRCh38>
+##contig=<ID=chr20,length=64444167,assembly=GRCh38>
+##INFO=<ID=DP,Number=1,Type=Integer,Description="Total read depth">
+##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
+##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read depth">
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO	FORMAT	P001
+chr1	11913838	.	A	T	87	PASS	DP=38	GT:DP	1/1:38
+chr1	33711661	.	G	C	61	PASS	DP=37	GT:DP	1/1:37
+chr1	45899293	.	C	T	74	PASS	DP=52	GT:DP	0/1:52
+chr1	138834739	.	T	G	70	PASS	DP=46	GT:DP	0/1:46
+chr1	139602254	.	G	T	84	PASS	DP=49	GT:DP	1/1:49
+chr1	162068500	.	A	G	57	PASS	DP=33	GT:DP	1/1:33
+chr1	227621759	.	C	G	88	PASS	DP=51	GT:DP	0/1:51
+chr17	43044294	.	A	C	62	PASS	DP=45	GT:DP	0/1:45
+chr17	43044295	.	C	G	91	PASS	DP=46	GT:DP	0/1:46
+chr17	43055276	.	G	A	86	PASS	DP=51	GT:DP	0/1:51
+chr17	43059666	.	G	A	55	PASS	DP=24	GT:DP	0/1:24
+chr17	43061329	.	G	A	75	PASS	DP=40	GT:DP	1/1:40
+chr17	43075071	.	C	G	70	PASS	DP=50	GT:DP	1/1:50
+chr17	43087473	.	A	C	52	PASS	DP=45	GT:DP	0/1:45
+chr17	43095759	.	C	T	52	PASS	DP=51	GT:DP	1/1:51
+chr17	43100876	.	G	T	93	PASS	DP=36	GT:DP	0/1:36
+chr17	43108081	.	T	C	60	PASS	DP=22	GT:DP	0/1:22
+chr17	43111166	.	C	A	71	PASS	DP=29	GT:DP	0/1:29
+chr17	43118559	.	T	C	56	PASS	DP=50	GT:DP	0/1:50
+chr17	43125483	.	C	T	76	PASS	DP=40	GT:DP	1/1:40
+chr17	43125484	.	G	C	89	PASS	DP=59	GT:DP	0/1:59
+chr19	44906345	.	T	G	62	PASS	DP=52	GT:DP	0/1:52
+chr19	44907272	.	T	G	85	PASS	DP=29	GT:DP	0/1:29
+chr19	44907527	.	G	C	78	PASS	DP=23	GT:DP	1/1:23
+chr19	44908684	rs429358	T	C	56	PASS	DP=58	GT:DP	0/1:58
+chr20	12657015	.	G	A	94	PASS	DP=39	GT:DP	0/1:39
+chr20	13974064	.	C	G	73	PASS	DP=22	GT:DP	0/1:22
+chr20	22188117	.	A	C	99	PASS	DP=47	GT:DP	0/1:47
+chr20	30588233	.	T	G	55	PASS	DP=22	GT:DP	0/1:22
+chr20	36112198	.	C	A	50	PASS	DP=38	GT:DP	1/1:38
+chr20	38576612	.	C	G	94	PASS	DP=26	GT:DP	0/1:26
+chr20	46050645	.	A	G	71	PASS	DP=36	GT:DP	0/1:36
+chr20	47351745	.	C	A	81	PASS	DP=24	GT:DP	1/1:24
+chr20	50908083	.	G	C	89	PASS	DP=49	GT:DP	0/1:49

examples/policy/P002.vcf

@@ -0,0 +1,35 @@
+##fileformat=VCFv4.3
+##fileDate=20260925
+##source=vcf-rdfizer-policy-demonstrator-fixture
+##reference=GRCh38
+##contig=<ID=chr1,length=248956422,assembly=GRCh38>
+##contig=<ID=chr17,length=83257441,assembly=GRCh38>
+##contig=<ID=chr19,length=58617616,assembly=GRCh38>
+##contig=<ID=chr20,length=64444167,assembly=GRCh38>
+##INFO=<ID=DP,Number=1,Type=Integer,Description="Total read depth">
+##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
+##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read depth">
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO	FORMAT	P002
+chr1	11913838	.	A	T	90	PASS	DP=47	GT:DP	0/1:47
+chr1	45899293	.	C	T	68	PASS	DP=54	GT:DP	0/1:54
+chr1	139602254	.	G	T	56	PASS	DP=34	GT:DP	1/1:34
+chr1	162068500	.	A	G	61	PASS	DP=35	GT:DP	1/1:35
+chr1	231965065	.	C	T	94	PASS	DP=57	GT:DP	0/1:57
+chr1	232595915	.	T	C	57	PASS	DP=27	GT:DP	0/1:27
+chr17	43061329	.	G	A	98	PASS	DP=32	GT:DP	0/1:32
+chr17	43075071	.	C	G	80	PASS	DP=52	GT:DP	0/1:52
+chr17	43087473	.	A	C	53	PASS	DP=58	GT:DP	1/1:58
+chr17	43095759	.	C	T	96	PASS	DP=37	GT:DP	1/1:37
+chr17	43111166	.	C	A	92	PASS	DP=32	GT:DP	0/1:32
+chr17	43118500	.	C	T	67	PASS	DP=29	GT:DP	0/1:29
+chr17	43124696	.	T	A	52	PASS	DP=56	GT:DP	1/1:56
+chr19	44907675	.	A	C	77	PASS	DP=22	GT:DP	0/1:22
+chr19	44908684	.	T	G	50	PASS	DP=28	GT:DP	1/1:28
+chr19	44908822	rs7412	C	T	55	PASS	DP=38	GT:DP	0/1:38
+chr20	12657015	.	G	A	82	PASS	DP=31	GT:DP	0/1:31
+chr20	13974064	.	C	G	65	PASS	DP=56	GT:DP	0/1:56
+chr20	36112198	.	C	A	55	PASS	DP=20	GT:DP	0/1:20
+chr20	38576612	.	C	G	63	PASS	DP=39	GT:DP	0/1:39
+chr20	46050645	.	A	G	86	PASS	DP=34	GT:DP	1/1:34
+chr20	47351745	.	C	A	51	PASS	DP=20	GT:DP	0/1:20
+chr20	50908083	.	G	C	72	PASS	DP=60	GT:DP	0/1:60

examples/policy/P003.vcf

@@ -0,0 +1,39 @@
+##fileformat=VCFv4.3
+##fileDate=20260925
+##source=vcf-rdfizer-policy-demonstrator-fixture
+##reference=GRCh38
+##contig=<ID=chr1,length=248956422,assembly=GRCh38>
+##contig=<ID=chr17,length=83257441,assembly=GRCh38>
+##contig=<ID=chr19,length=58617616,assembly=GRCh38>
+##contig=<ID=chr20,length=64444167,assembly=GRCh38>
+##INFO=<ID=DP,Number=1,Type=Integer,Description="Total read depth">
+##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
+##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read depth">
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO	FORMAT	P003
+chr1	33711661	.	G	C	53	PASS	DP=20	GT:DP	0/1:20
+chr1	45899293	.	C	T	70	PASS	DP=20	GT:DP	0/1:20
+chr1	138834739	.	T	G	92	PASS	DP=35	GT:DP	1/1:35
+chr1	152491455	.	A	G	56	PASS	DP=42	GT:DP	0/1:42
+chr1	231965065	.	C	T	69	PASS	DP=22	GT:DP	0/1:22
+chr1	232595915	.	T	C	62	PASS	DP=47	GT:DP	0/1:47
+chr17	43055276	.	G	A	59	PASS	DP=50	GT:DP	1/1:50
+chr17	43059666	.	G	A	91	PASS	DP=43	GT:DP	1/1:43
+chr17	43061329	.	G	A	85	PASS	DP=35	GT:DP	1/1:35
+chr17	43075071	.	C	G	52	PASS	DP=50	GT:DP	0/1:50
+chr17	43087473	.	A	C	65	PASS	DP=38	GT:DP	1/1:38
+chr17	43095759	.	C	T	69	PASS	DP=24	GT:DP	0/1:24
+chr17	43100876	.	G	T	69	PASS	DP=33	GT:DP	0/1:33
+chr17	43108081	.	T	C	79	PASS	DP=46	GT:DP	0/1:46
+chr17	43124696	.	T	A	54	PASS	DP=22	GT:DP	1/1:22
+chr19	44906345	.	T	G	75	PASS	DP=57	GT:DP	0/1:57
+chr19	44907272	.	T	G	95	PASS	DP=35	GT:DP	0/1:35
+chr19	44907527	.	G	C	51	PASS	DP=33	GT:DP	1/1:33
+chr19	44907675	.	A	C	52	PASS	DP=27	GT:DP	0/1:27
+chr19	44908684	rs429358	T	C	60	PASS	DP=33	GT:DP	0/1:33
+chr19	44908822	rs7412	C	T	58	PASS	DP=39	GT:DP	0/1:39
+chr20	13974064	.	C	G	68	PASS	DP=27	GT:DP	0/1:27
+chr20	20513631	.	T	A	51	PASS	DP=44	GT:DP	0/1:44
+chr20	22188117	.	A	C	68	PASS	DP=44	GT:DP	0/1:44
+chr20	30588233	.	T	G	58	PASS	DP=47	GT:DP	0/1:47
+chr20	36112198	.	C	A	60	PASS	DP=40	GT:DP	1/1:40
+chr20	38576612	.	C	G	85	PASS	DP=23	GT:DP	1/1:23

examples/policy/P004.vcf

@@ -0,0 +1,38 @@
+##fileformat=VCFv4.3
+##fileDate=20260925
+##source=vcf-rdfizer-policy-demonstrator-fixture
+##reference=GRCh38
+##contig=<ID=chr1,length=248956422,assembly=GRCh38>
+##contig=<ID=chr17,length=83257441,assembly=GRCh38>
+##contig=<ID=chr19,length=58617616,assembly=GRCh38>
+##contig=<ID=chr20,length=64444167,assembly=GRCh38>
+##INFO=<ID=DP,Number=1,Type=Integer,Description="Total read depth">
+##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
+##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read depth">
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO	FORMAT	P004
+chr1	11913838	.	A	T	76	PASS	DP=43	GT:DP	0/1:43
+chr1	33711661	.	G	C	64	PASS	DP=29	GT:DP	0/1:29
+chr1	45899293	.	C	T	74	PASS	DP=48	GT:DP	0/1:48
+chr1	138834739	.	T	G	61	PASS	DP=45	GT:DP	0/1:45
+chr1	139602254	.	G	T	89	PASS	DP=31	GT:DP	1/1:31
+chr1	231965065	.	C	T	98	PASS	DP=25	GT:DP	0/1:25
+chr1	232595915	.	T	C	76	PASS	DP=28	GT:DP	1/1:28
+chr17	43055276	.	G	A	81	PASS	DP=31	GT:DP	0/1:31
+chr17	43059666	.	G	A	82	PASS	DP=49	GT:DP	0/1:49
+chr17	43075071	.	C	G	52	PASS	DP=50	GT:DP	0/1:50
+chr17	43087473	.	A	C	65	PASS	DP=37	GT:DP	0/1:37
+chr17	43095759	.	C	T	65	PASS	DP=24	GT:DP	0/1:24
+chr17	43108081	.	T	C	99	PASS	DP=31	GT:DP	0/1:31
+chr17	43118500	.	C	T	83	PASS	DP=27	GT:DP	0/1:27
+chr17	43118559	.	T	C	73	PASS	DP=23	GT:DP	1/1:23
+chr17	43124696	.	T	A	51	PASS	DP=52	GT:DP	0/1:52
+chr19	44907272	.	T	G	96	PASS	DP=50	GT:DP	0/1:50
+chr19	44907675	.	A	C	68	PASS	DP=30	GT:DP	1/1:30
+chr19	44908684	rs429358	T	C	80	PASS	DP=58	GT:DP	0/1:58
+chr20	12657015	.	G	A	79	PASS	DP=28	GT:DP	1/1:28
+chr20	13974064	.	C	G	98	PASS	DP=27	GT:DP	0/1:27
+chr20	20513631	.	T	A	85	PASS	DP=27	GT:DP	0/1:27
+chr20	30588233	.	T	G	85	PASS	DP=26	GT:DP	0/1:26
+chr20	36112198	.	C	A	54	PASS	DP=35	GT:DP	0/1:35
+chr20	47351745	.	C	A	55	PASS	DP=31	GT:DP	0/1:31
+chr20	50908083	.	G	C	95	PASS	DP=58	GT:DP	0/1:58

examples/policy/P005.vcf

@@ -0,0 +1,41 @@
+##fileformat=VCFv4.3
+##fileDate=20260925
+##source=vcf-rdfizer-policy-demonstrator-fixture
+##reference=GRCh38
+##contig=<ID=chr1,length=248956422,assembly=GRCh38>
+##contig=<ID=chr17,length=83257441,assembly=GRCh38>
+##contig=<ID=chr19,length=58617616,assembly=GRCh38>
+##contig=<ID=chr20,length=64444167,assembly=GRCh38>
+##INFO=<ID=DP,Number=1,Type=Integer,Description="Total read depth">
+##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
+##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read depth">
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO	FORMAT	P005
+chr1	11913838	.	A	T	71	PASS	DP=25	GT:DP	0/1:25
+chr1	33711661	.	G	C	72	PASS	DP=56	GT:DP	0/1:56
+chr1	45899293	.	C	T	87	PASS	DP=47	GT:DP	0/1:47
+chr1	138834739	.	T	G	51	PASS	DP=47	GT:DP	1/1:47
+chr1	139602254	.	G	T	87	PASS	DP=26	GT:DP	1/1:26
+chr1	152491455	.	A	G	66	PASS	DP=40	GT:DP	0/1:40
+chr1	231965065	.	C	T	50	PASS	DP=25	GT:DP	0/1:25
+chr1	232595915	.	T	C	58	PASS	DP=50	GT:DP	1/1:50
+chr17	43055276	.	G	A	75	PASS	DP=54	GT:DP	0/1:54
+chr17	43059666	.	G	A	98	PASS	DP=55	GT:DP	0/1:55
+chr17	43087473	.	A	C	94	PASS	DP=23	GT:DP	1/1:23
+chr17	43095759	.	C	T	91	PASS	DP=27	GT:DP	1/1:27
+chr17	43100876	.	G	T	51	PASS	DP=35	GT:DP	0/1:35
+chr17	43111166	.	C	A	68	PASS	DP=31	GT:DP	0/1:31
+chr17	43118500	.	C	T	56	PASS	DP=47	GT:DP	0/1:47
+chr17	43118559	.	T	C	68	PASS	DP=22	GT:DP	0/1:22
+chr17	43124696	.	T	A	54	PASS	DP=58	GT:DP	1/1:58
+chr19	44907675	.	A	C	82	PASS	DP=57	GT:DP	0/1:57
+chr19	44908684	rs429358	T	C	67	PASS	DP=43	GT:DP	0/1:43
+chr19	44908822	rs7412	C	T	84	PASS	DP=34	GT:DP	1/1:34
+chr20	12657015	.	G	A	95	PASS	DP=60	GT:DP	0/1:60
+chr20	13974064	.	C	G	56	PASS	DP=43	GT:DP	0/1:43
+chr20	20513631	.	T	A	81	PASS	DP=21	GT:DP	0/1:21
+chr20	22188117	.	A	C	80	PASS	DP=44	GT:DP	0/1:44
+chr20	36112198	.	C	A	74	PASS	DP=28	GT:DP	0/1:28
+chr20	38576612	.	C	G	92	PASS	DP=55	GT:DP	0/1:55
+chr20	46050645	.	A	G	59	PASS	DP=53	GT:DP	1/1:53
+chr20	47351745	.	C	A	82	PASS	DP=28	GT:DP	0/1:28
+chr20	50908083	.	G	C	99	PASS	DP=20	GT:DP	1/1:20

examples/policy/README.md

@@ -0,0 +1,106 @@
+# Policy attachment example (v0.1.0)
+
+One synthetic cohort, one set of ODRL policies, three requesters, and three
+different release views, each checked against the source VCFs. How the engine
+works (select → partition → decide, each configured in Turtle) is in
+[`docs/policy-demonstrator.md`](../../docs/policy-demonstrator.md).
+
+This is **governed release, not anonymization.** Views keep the original IRIs,
+and a released genotype still identifies the person it came from.
+
+## Run it
+
+```bash
+examples/policy/run_demo.sh /tmp/policy-demo     # needs rdflib; no Docker
+PROFILE=condensed examples/policy/run_demo.sh /tmp/policy-demo-condensed
+```
+
+It explains the policy, attaches it to the graph, and then for each requester
+evaluates a view and checks it. Finally it prints the decision grid:
+
+```text
+requester P001.vcf  P002.vcf  P003.vcf  P004.vcf  P005.vcf  triples withheld
+alz       22        16        18        withheld  20        4649
+clinical  33        23        withheld  withheld  withheld  6539
+gru       21        16        withheld  withheld  withheld  7869
+```
+
+Each number is the records released from that file. Where P001 and P002 differ
+between requesters, that's the cohort rules at work. *BRCA1* records are
+released only for clinical care, and the APOE ε4 variant (rs429358) only for
+disease-specific research. P004 withdrew.
+
+## What is here
+
+| File | What it is |
+| --- | --- |
+| `make_fixture.py` | Deterministic generator for the five VCFs and `fixture.json` |
+| `P001.vcf` … `P005.vcf` | One synthetic participant each, GRCh38, 23–34 records |
+| `fixture.json` | Seed, loci, each participant's consent, and the three requesters |
+| `policy.ttl` | Five consents (one per file) and the cohort policy (*BRCA1*, ε4) |
+| `custom-selector.ttl` | A selector type declared in the policy itself (below) |
+| `converted/` | The VCFs converted once per sample profile, so nothing needs Docker; see `PROVENANCE.json` |
+| `run_demo.sh` | The walkthrough above |
+
+The positions are real GRCh38 coordinates in real loci, and rs429358 and
+rs7412 are the real variants. Every other allele, and every genotype, is
+synthetic. To regenerate the fixture, run
+`python3 examples/policy/make_fixture.py`.
+
+## The pieces, one at a time
+
+```bash
+vcf-rdfizer-policy explain  --policy policy.ttl
+vcf-rdfizer-policy attach   --rdf converted/expanded/P00*.nt.gz --policy policy.ttl -o annotated.nt
+vcf-rdfizer-policy evaluate --rdf converted/expanded/P00*.nt.gz --policy policy.ttl \
+    --assignee https://example.org/party/alz-consortium --purpose DUO:0000007 -o views/alz
+vcf-rdfizer-policy check    --view views/alz --rdf converted/expanded/P00*.nt.gz \
+    --policy policy.ttl --vcf P00*.vcf
+```
+
+`evaluate` writes the following into its output directory:
+- `view.nt`, the released triples;
+- `decisions.csv`, one row per record with the rule that decided it;
+- `summary.json`, the counts;
+- `manifest.ttl`, the policy's digest, the request, what was withheld and the
+  obligations accepted.
+
+`check` runs the structural checks against the source graph. With `--vcf`, it
+also re-derives the expected records straight from the VCF text and fails on
+any difference.
+
+## Write your own selector
+
+Selector types are SPARQL, declared in Turtle, and there is nothing to code.
+`custom-selector.ttl` declares one inside the policy that uses it:
+
+```turtle
+ex:QualityBelow a vcfp:SelectorType ;
+    vcfp:parameter ex:threshold ;                      # bound to ?threshold
+    vcfp:query """
+        PREFIX vcfc: <https://w3id.org/vcf-core/vocab#>
+        SELECT ?resource WHERE {
+            ?resource a vcfc:VCFRecord ; vcfc:hasCall ?call .
+            ?call vcfc:qual ?qual .
+            FILTER(?qual < ?threshold) }""" .
+
+ex:low-quality a odrl:Asset , vcfp:GraphSelection ;
+    vcfp:selector [ a ex:QualityBelow ; ex:threshold 60 ] .
+```
+
+With every file released for general research except that selection, 38 of
+the 139 records are withheld:
+
+```bash
+vcf-rdfizer-policy evaluate --rdf converted/expanded/P00*.nt.gz --policy custom-selector.ttl \
+    --assignee https://example.org/party/anyone --purpose DUO:0000042 -o views/quality
+```
+
+The query must project `?resource`. Each `vcfp:parameter` names a property of
+the selector node, bound to the variable of the same local name. A selector
+type can also carry a `vcfp:violations` query, and any row it returns stops
+evaluation; the shipped region and variant selectors use one to check the
+assembly.
+
+To share a selector across policies, put it in a file and pass
+`--profile vcf-core --profile my-selectors.ttl`.